Why Did Bernard Kerr's Prototype Frame Break at Crankworx Rotorua?

Mar 18, 2024 at 20:24
by Mike Kazimer  

A catastrophic frame failure in the middle of a race run is a nightmare scenario for any professional athlete, and for the company that manufactured the frame. Unfortunately, that's exactly what happened to Bernard Kerr and his prototype Pivot during the Crankworx Rotorua DH race this past weekend. Towards the bottom of his run he pulled up for a triple and came up short, with the front end of his bike separating on impact, as the above video demonstrates. Thankfully, Bernard wasn't seriously injured, but it's still the last thing anyone wants to see happen.

Chris Cocalis, Pivot's founder and CEO, provided the following insight into what likely caused the frame to break:

bigquotesAfter a preliminary investigation into the failure of the prototype frame, we have identified that there was no failure of the carbon tubes and the epoxy used to bond the frame was still intact on the carbon tube side. Unfortunately, virtually no adhesive remained bonded to the aluminum. We use a treatment on all the aluminum parts to protect from galvanic corrosion between the carbon and the aluminum. We believe there was a failure of this treatment to properly etch/adhere to the aluminum.

We have additional frames that were made in the same batch, which we will be putting through full destructive testing as well as getting all the frames from the team back that were produced at the same time. Once we have the opportunity to test these prototype frames, we will take the necessary steps to ensure that the frames are as safe as possible, and ready for the full impact of another World Cup season.

We never want to see a frame failure and certainly not a failure of this magnitude. We are incredibly thankful that Bernard was not seriously injured and are taking steps to make sure that this is not an issue in the future.
Chris Cocalis, Founder & CEO, Pivot Cycles

Photo Credit Dario DiGiulio
One of the prototype frames being assembled at Pivot's Phoenix, Arizona, headquarters.

Racers often serve as test pilots, putting hard miles in on bikes and equipment before they're launched to the public. Lab testing can only go so far, which is why real world testing is still an integral part of the development process. In this case, Pivot has been developing the new DH bike out in the open, allowing the general public to trace its progress over the course of last year's World Cup DH season.

The frame that broke had been raced at Hardline and seen numerous practice runs put on it in the lead-up to the Crankworx DH finals, so it hadn't exactly had an easy start to its life. Still, an instance like this does illustrate just how quickly things can go wrong. It is good to see that Pivot are already working to correct the issue, and we look forward to seeing Bernard and the rest of the Pivot DH team on track when the World Cup season kicks off at Fort William.

Bernard Kerr warming the hips up for some race run break dancing.
BK sending a whopper at Crankworx Rotorua before things took a turn for the worse.

Author Info:
mikekazimer avatar

Member since Feb 1, 2009
1,743 articles

  • 495 38
 One word: Prototype. That frame took WAY more abuse than most of us mortals would put it thru in 5 seasons. I mean....Hardline race alone was a beast of a race. Prototypes break, they adjust and move on. Glad Kerr wasn't seriously injured (I hope). Part of racing at the pointy end.
  • 231 328
flag jostaudt (Mar 18, 2024 at 20:56) (Below Threshold)
 Frames (even prototypes) that get raced should NOT break! It puts a rider‘s life at risk. All of these construction processes are well known. Messing up the process for a high consequence step like anti-galvanic corrosion treatment is negligence.
  • 231 34
 @jostaudt: Saying prototypes shouldn't break is naive at best. Pro racers have been testing AND breaking prototypes since pretty much bike racing was invented (Road, Track, BMX, MTB, etc). Simple as that
  • 92 1
 It's like people forgot how Bernard Kerr got on pivot in the first place!
  • 61 1
 Anyone who's been around racing long enough would have seen plenty of bikes break. Ive had athletes say they were told to ride it until they break it. Hopefully BK is all good, but I'm sure he's busted up plenty of bikes in the past, just unfortunate for Pivot that it happened during the broadcast.
  • 18 38
flag JohSch (Mar 18, 2024 at 22:32) (Below Threshold)
 @jostaudt: about all of those bike companies/brands are small scale garage shops aka "Bastelbuden" and not overly great or experienced in carrying out good manufacturing process quality and probably don't know enough about the techniques they're using and the shortcomings / traps

Manufacturing is what (hopefully) their Asian suppliers are good at.
  • 37 37
Completely right.
This was a production fault.
  • 28 9
 @Bomberone: In case you didn't know, I'm a PB Fantasy League Racer. But anyway, pretty much all Racing (all motorsports, anyway) is done on Prototype parts.
  • 12 136
flag TokenCanfieldGuy (Mar 18, 2024 at 23:31) (Below Threshold)
 I didn't know it was possible to hate Pivot bike TRASH anymore than I already did....I gotta commend their ability to help 'innovate' more hate within my heart. Kudos
  • 52 16
 @fektor-b: Cracks and minor issues like we‘ve seen with the Frameworks frames is acceptable and part of testing but a catastrophic failure like this one is different. That should not happen. Makes me wonder what these riders have written in their contracts in case of major consequences…
  • 11 12
 @jostaudt: Spoke with a friend who works is automotive a while ago, he was on a team that developed a new part for racing cars, it was pretty critical part of an engine and during first testing 100% of their parts failed. Also dont forget when Boeing put a pretty much prototype system on their airplanes which eventually crashed two of them...
  • 6 2
 How do you know that that frame is the same one used in the other events?
  • 34 5
 If the wheels held up casing that knuckle, the frame should have.
  • 38 13
 Being a prototype doesnt excuse it from critisim or mean its understandable to have a critical failure. Tyler Waite was on the Yeti prototype and cased the living shit out of the same triple but that frame was fine.
  • 25 3
 @winko: Well, as of latest news it seems that Boeing supplies prototypes only to their customers.
  • 409 30
 Naw, it’s a fundamentally flawed design and manufacturing process (in terms of composites engineering), from what I can see from their prototype manufacturing pictures, as well as from Kerr’s broken frame pictures — in my opinion. Also, the fact that something is a prototype doesn’t mean that it’s permissible to utilize a dangerously designed / engineered / manufactured product, which could result in the substantial impairment or death of an athlete.

The first flaw is the straight-insertion of the top tube AND the down tube into the lug, at the same draw angle. As such, if the bond isn’t perfect and the bondline fractures, the tubes are not mechanically constrained by different draw angles...both tubes pull out of the lug(s) in the exact same draw direction — that is a serious design / engineering flaw in my professional (composites engineering) opinion. If designed differently, with different draw angles for each tube / lug, both tubes likely would not experience the same stress vectors at the bondine (due to their varying orientation) and thus both bondlines likely wouldn’t fail at the same time. And both tubes would not (and could not) pull out of the lug(s) at the same time, in the same direction. With different draw angles / bondline orientation / stress vectors, one bondline would likely fail before the other, allowing detection of the bond failure. Likewise, the different draw angles (if the tube are stiff & strong enough) wouldn’t allow both tubes to pull out at the same time, in the same direction. Atherton got that right. Pivot got that wrong. It was a major oversight and a fundamental engineering flaw, in my opinion. That Pivot frame even has a separate individual top tube, and a separate individual down tube — so they didn’t need to utilize the same draw angle for both the top tube & down tube. (But the same draw angle would be required if the rest of front triangle was a single-piece composite molding and the top and down tubes weren’t separate pieces).

Also, if the bondline wasn’t perfect, bonding failures can occur from bonding adhesive microcracking, adhesive macro-cracking, and incomplete adhesive coverage. Galvanic corrosion, and other corrosion, can be an issue with aluminum lugs and carbon fiber (unless the carbon fiber is insulated with fiberglass or similar non-conductive material). Aerospace companies often use fiberglass layers to prevent galvanic corrosion, making sure to not sand them off, nor sand too deeply into the fiberglass, where it bonds to aluminum. Likewise, at a minimum, they’ll typically hard anodize the aluminum, or use another bonding-optimized mil-spec surface preparation or treatment and/or anodizing process. Often, aerospace companies apply a military-spec type of cured epoxy primer onto the aluminum, to which the subsequent prepreg composite, or bonding adhesive, can tenaciously bond (and bond without corrosion due to the protective anti-corrosion epoxy coating). It appears Pivot excluded some or all of these critical (and fairly simple) steps. I also don’t see any fiberglass on the cured tubes, in the bonding area, in the prototype manufacturing pictures that Pivot released for publication on Pinkbike — it appears to be solely a woven carbon fiber surface layer, with no galvanic insulation layer, in the area bonded to the lug.

Additionally, it appears the bonding process was flawed — I didn’t seem to see much adhesive on the composite nor aluminum portions of the failed bond (in Kerr’s broken frame pictures). There’s a chance they didn’t properly remove mold release on the cured composite tubes. Or that they didn’t properly prepare the composite & aluminum surfaces (via abrasion and solvent cleaning), or that insufficient bonding adhesive was used, or that the adhesive scraped out of place during the assembly process...thus resulting in insufficient adhesive in the area to be bonded. The bonding process also appears suspect, from what I’ve seen in various pictures of the frame & manufacturing process. Trek (OCLV) and others co-mold several 0.002” tall “pips” around the circumference and length of their “male” bonded tubes...those pips center the tube into the female lug (or tube) and ensure an optimal 0.002” thick bondline, and it ensures that the adhesive doesn’t get scraped out of place as the tube is inserted. I doubt Pivot did anything like those 2-thou pips, based on several of my observations. It’s also usually a good idea to “inject” a bit of structural epoxy bonding adhesive into a port at the bonded joint, after initial assembly with adhesive, to ensure the entire bondline is fully covered, saturated, and void-free. I don’t see that sort of adhesive-injection port feature on their frame (from my cursory review), but I think Specialized might do that on their prototype DH frames. I think Atherton does the same. It’s common in aerospace, F1, and even in the production of certain composite sports cars. I actually import special 3M structural adhesive from the UK (it’s what I used on McLaren’s carbon fiber “tubs” and Bentley Motors’ prototype carbon fiber doors for one of their Super Sports technology demonstrator cars) which is better than what’s available in the US (likely because it’s more toxic =) — it’s strong, and has superior mechanical & dynamic performance numbers, and is highly toughened (as well as being highly crosslinked for extra strength, if you post-cure it a bit around 250F to 350F after achieving initial bond strength at room temp, overnight. Engineers, prototype manufacturing technicians, and production manufacturing technicians, cannot mess around with bond failures — it has to be done right, and the materials and manufacturing processes have to enable bonding perfection. Every time.

Also, Pivot appears to use cast-silicone custom bladders for their prototypes — and silicone / silicone oil can readily leach into the prepreg (unless significant protective countermeasures are taken). The silicone contamination can greatly adversely affecting bonding / adhesion. Aerospace companies ban everything silicone in their composites manufacturing facilities, for this reason. Even those yellow silicone “Livestrong” Lance Armstrong bracelets are strictly banned. Pivot’s custom composite tubes could have been contaminated with silicone that could affect their adhesive-bond performance — and their manufacturing pictures show the silicone bladder directly in contact with the uncured & cured carbon fiber prepreg, directly adjacent to the end of the tube (where the composite tube is subsequently bonded). Polyurethane, latex, molded nylon, or nylon film over polystyrene foam rigidized-bladder mandrels, are good alternatives for prototypes (and sometimes production).

Lastly, the kink / bend in the carbon fiber downtube, just behind the lug, will put both sides of the downtube in compression right at the kink / downtube bend...and carbon fiber fails in compression. Although Kerr’s bike didn’t fail there, it’s a suboptimal compression-loading scenario which will result in pronounced compressive forces in the laminate on both the top and bottom sides of the downtube at the bend (in a jump-case loading scenario like Kerr experienced). Frames have to be engineered, in every way, for those worst-case cases...and engineering a frame with a tube geometrical configuration that results in substantial compressive forces on both sides of a composite tube is just questionable engineering, in my opinion. The goal should be to limit inducing those sort of compressive loads and mitigate the risk of composite compressive failure.
  • 130 1
 @WRCDH: you sound like you know what you're on about
  • 15 1
 @WRCDH: Where are Kerr's broken frame pictures?

Also, Atherton uses titanium lugs while Pivot used aluminum lugs. I'm no expert and just a guess, but could the titanium being more resistant to corrosion than alumunium be a factor?
  • 165 0
 @WillW123: Ikr, someone should really explain to him that this is PinkBike and comments should be baseless, accusatory and inflammatory rather than measured, researched and well explained
  • 18 1
 @WRCDH: Best analysation by far. Very interesting backround knowlege you have here. Thanks for sharing !
Do you know what adhesive atherton bikes or Spezialized uses for their prototypes ?
  • 8 23
flag KalkhoffKiller (Mar 19, 2024 at 2:07) (Below Threshold)
 @winko: it comes down to how much a company values safety over profit and how its regulated on a state level. Just compare boeing to airbus or tesla to japanese manufacturers. Clearly there are different ethics at play from top to bottom which have their consequences.
  • 4 20
flag NelsonRidela (Mar 19, 2024 at 2:07) (Below Threshold)
 @jostaudt: Karen
  • 15 2
 Don't they state these bikes are just lugged for a prototype stage and the final product will be full carbon oce they get geo and so on dialled in ?

I think a lot of bike may of cracked or broken with the amount of forces that went through that frame and the angle of the landing, these things happen look at GT brand new DH bike it snapped clean in half in front of the world but people like Danny Hart are riding it without the same issues and Greg's V10 a few years ago I know it hit a tree but look how many other bikes (even the same models) have had similar crashes and nothing has happened. It was a freak accident that happned on the world stage the amount of bikes that break while testing and not being seen would probably shock everyone but you don't get to see or hear about it
  • 5 12
flag deadmeat25 (Mar 19, 2024 at 2:48) (Below Threshold)
 @jostaudt: Wow, you're wasted at that shelf stacking job, you sound like such an engineering genius....
  • 11 10
 @jostaudt: I cannot these people are defending this public excuse. If you race hardline after you replace the frame if you think it has been through too many impacts outside the simulation boundaries.
Honestly I think large frame manufacturers are having troubles sourcing the right talent.
A failure of this magnitude could have caused the death of an athlete, then I would like to see their sorry faces.
  • 15 1
 @winko: You're creating false equivalences. In the motorsports case, if that engine was going to shoot a rod through the driver's head, there is no way it would have been allowed. Look at the crashes that F1 drivers walk away from, there is a mandatory level of safety for the drivers and spectators that are met and is managed by the relevant motor sport association. In the case of Boeing... corporate negligence, underfunded certification organizations among other things. That should serve as an example of failure and _not_ as a roll model.

I _do_ agree that in racing there is a risk of prototypes breaking, but fundamental process problems like this case are _not_ what you want as a point of failure. Carbon layups and bonding are not garage-sport technologies and the companies involved in them need to have a certain amount of resources available to do things right. How Pivot analyzes, improves and moves on will say a lot about their engineering/manufacturing credentials.
  • 15 0
 @jostaudt: production frames break all the time in world cup DH. It just isn't usually this public.
Last year there was at least one full head tube separation on a production frame.
  • 13 23
flag slayersxc17 (Mar 19, 2024 at 3:25) (Below Threshold)
 @WRCDH: I didn’t even read all the words in this article, no way I’m getting thru this
  • 3 1
 @tacklingdummy: Correct, Titanium lugs, which thankfully dont suffer from the same galvanic corrosion issues.
  • 24 1
 @WillW123: Haha, thx! But don’t tell anyone — I’m just getting more proficient at faking it until I make it =)

But I’ll tell ya, despite my prototype Pivot DH bike engineering thrashing, I’ve utterly thrashed my own Pivot Mach 4 with zero failures in 7+ years — it’s a 28.5 pound (13.0kg), with pedals, aluminum 26” Pivot Mach 4 cross country bike that I ride like a DH and/or slalom bike (the Avalanche cartridge in the 120mm fork really helps =). I still can’t believe how well that bike rides...climbs well and goes downhill even better. Then again, Pivot’s M4X (4X / slalom frame) was just a slightly modified Mach 4. Some pics & vids below!

Haleakala Schleyble-Top:
Greenlake wheelie fake?
Maui Waui manual-lander:
My best Myles Rockwell pose (no Maui Waui involved tho):
Never lift when you drift:

Trying to destroy my Mach 4:
You steer a bike with the rear wheel:
  • 17 2
 @WRCDH: Hope they don't venture in to underwater engineering.
  • 12 0
 @Beicpinc: Dude, for real — I know a few of the Seattle-area people and companies who made the composites for that sub! Bad idea from the start.
  • 46 1
 @WRCDH: This is probably the best article ever published on Pinkbike. You're hired.
  • 2 1
 @slayersxc17: LOL, me either...I just now saw Chris’ quote in the article, haha.
  • 11 0
 Adhesive failure means the load bearing capability is very low - it's a binary situation - either very strong or very weak. Basically there is just friction holding the tube in place - this could have failed just riding trails.
I have designs (and most importantly the process control developed and defined) in space applications and commercial planes that rely on surface preparation of aluminum for adhesion. We normally use plasma etching, a primer and a curing oven before bonding). The loads and the lifetime requirements are pretty challenging. I guess that on a MTB those challenges are even more difficult ... plus the consequences.
  • 1 15
flag OpeSorryAbootThat FL (Mar 19, 2024 at 3:54) (Below Threshold)
 @slayersxc17: you can ignore most of what he said anyways since it's irrelevant or wrong.
  • 2 1
 @winko: You don’t know what you’re talking about. Be quiet.
  • 2 0
 @blacktea: it literally says so in the article…
  • 15 6
 @WRCDH: Guy just absolutely dismantled Pivot bikes in a single post.
How could we trust anything they "innovate" with future designs, real question.
  • 10 0
 @tacklingdummy: Here is one of Kerr’s broken frame pics:
  • 1 0
 @WillW123: your comment made me laugh.
  • 4 1
 @WRCDH: Too long to be wrong!
  • 3 1
 i dont care about how or why i just know theres no way i would trust it from that point onwards especially as prototypes are usually meticulously assembled and it still failed!
  • 4 8
flag sanchofula (Mar 19, 2024 at 5:59) (Below Threshold)
 @suspended-flesh: this has got to be the funniest thing I’ve read in a long time, as if being a fantasy racer makes you knowledgeable about racing, eccentric sure, but a mountain bike racer, not even close
  • 5 26
flag sanchofula (Mar 19, 2024 at 6:00) (Below Threshold)
 @WRCDH: holy shite, who’s gonna read that?
  • 3 0
 @blacktea: because the article says so....
  • 1 0
 @WRCDH: What do you think of the atherton released today, alu lugs and tubes but still bonded?
  • 6 2
 Prototype or not a frame breaking is a safety issue that we should think of as up there with a helmet failing. It's reasonable that people are questioning Pivot because this frame broke in a way an aluminum test mule would not have.
  • 9 0
 @WRCDH: So, back in the early 90's Trek OCLV frames DID fail. Carbon and aluminum. I had 2 Trek 9000 frames fail, in 2 different locations. Tubes just came apart, no shearing. I know, horrible bike, but that's what we had back then. I also saw Giant Cadex and a Specialized (hardtail around 1993) carbon tube lugged frames fail. It was always an issue. I think side loads and twisting slowly works away at the bond and fails. Some manufacturers added rivets near the end of the lugged frame run, but if you had a frame fail, you bought a welded frame after that experience. Haven't ridden an epoxy lugged frame in 30 years and never will again. It was bad.
  • 14 0
 @WRCDH: 10/10, I now consider myself a composites expert
  • 4 0
 @sanchofula: I did and loved every word of it. Then again, it is slightly relevant to my day job. Smile
  • 3 0
 The real reason has emerged: they wanted to spoil the Atherton bike launch.
  • 4 28
flag brapaholics (Mar 19, 2024 at 7:33) (Below Threshold)
 @WRCDH: i aint reading all that. congrats or sorry for your loss
  • 28 1
 @WRCDH: This x1000!! As someone who used to travel the country training aerospace companies how to properly perform different types of adhesive bonding, I can say you are 100% accurate in your analysis.

The frame failure is similar to what happens when too much primer is used, surface contamination (silicone), or lack of basic surface prep (one could argue all of these are examples of).

Pivot said they believe the failure was the material used to limit corrosion. Amazingly it sounds like they didnt do lap shear testing of various material, thicknesses, and surface prep. Or if they did, it sounds like they need to update process and procedures for the technicians.

Ultimately, this is just an example of new engineering, failures happen and we learn. Glad Kerr is not hurt, want to see this bad ass get the #1win !!!
  • 3 0
I noticed between the Atherton and Pivot, their cable ports are in different locations. The Pivot looks like it's lost 30-40% bonding area on the down tube and Lug.

What are you thoughts on that? Seem like a complete oversight.
  • 2 3
 The pictures are blurry, but the lugs look clean and doesn't look like there is any signs of bonding epoxy. Could they have forgotten to even use any bonding epoxy on those joints? Perhaps, like the Boeing mistake. Whenever I break an epoxy bonds with heat, there is always epoxy residue. Just a conspiracy theory from someone who uses epoxy a lot and breaks epoxy joints a lot with golf clubs.
  • 2 0
 @hgardner: I for one don't trust him, didn't mention anything about the benefits of headset cable routing. Clearly not all there.
  • 1 0
 @hgardner: best comment by far hahahha
  • 9 0
 @WRCDH: I just learned more here than in all of university
  • 5 0
 Some nice, light bathroom reading
  • 1 1
 @WRCDH: how long did it take you to write this?
  • 1 0
 @WRCDH: exactly
  • 2 0
 @bman33: "prototypes" in the bicycle world are actually "first production". That's not what most other industries would consider a "prototype". This is in fact a real prototype.
  • 4 0
 @WRCDH: I think you're onto something with the uni-directional insertion of the top and down tubes. If you angled them in the same manner of a traditional bike frame design, they would have used counteracting forces to literally keep the frame together; structural strength on top of bond strength. Not to say that the bond couldn't fail, but I think maybe if the insertion angles were different it wouldn't *catastrophically* fail. Also, there's zero need for the down tube to have that flat section that's often designed into bike frames for single crown fork clearance, and it would be useless for a bike intended to be used with a double crown. The traditional "true" triangle frame design has worked for brazed steel lug frames for over a century — Pivot should have been taking notes.
  • 6 0
 @WRCDH: Whoa fascinating analysis.

Perhaps they went with the sketchy parallel straight entry top and downtube to allow for front center/ reach geometry changes without changing the headtube CNC assembly dimensions?

With an Atherton I imagine they have a headtube lug CAD design for each of their geometry options, because the angles between top tube and downtube change with different reaches.

This way they can change reach without having to make a new headtube shape each time.

Maybe that's the point of the questionable bent down tube as well? The bend allows them to just cut the down tube to the desired front center/ reach?
  • 6 0
 @eastonsmith: the bent downtube helps the front tire clearance when bottoming out the fork.
  • 1 1
 @WillW123: Thanks...chat gpt?
  • 5 1
 The frame is only 1 month old. To have a joint failure on a new frame is fairly catastrophic
  • 4 0
 @WRCDH: maaan you killed it! Respect!
  • 1 0
 @jokermtb: ah yes forgot about that.
  • 3 0
 @blacktea: If you follow the team, I recommend you do cos it’s well worth it, you’ll see they are open about when a freshy arrives. This one arrived for BK to test RBHA - did you see the big hit on the first drop off the new container drop that led to a change in the landing? It then went back to NZ, then back to Tas and prepped and raced RBHA. Then back to NZ QT, then to Rotorua for CWR. Used for training extensively before each event.
  • 1 19
flag Azrocktester (Mar 19, 2024 at 12:38) (Below Threshold)
 @WRCDH: ...your a clown !
  • 2 1
 @sanchofula: Thanks, I'll be here all week.
  • 3 0
 @WRCDH: thanks for open my mind
  • 5 0
 @jostaudt: it's beyond me why you are getting downvoted.
Good to read some good old german engineering thoughts on this one.
  • 4 0
 I get what people are saying on both sides.

As far as the "prototypes break" that's very true. But in 2024 the fatigue/failure points of carbon and aluminum are pretty well known. In years past it was "hey the frame failed but we learned something and are adjusting our layup." Those failures make the finished product stronger or even carry over into early generations of the finished product (v1 Yeti Sb6). This failure isn't like that. It's a defect that will not help or hurt the finished product. It's embarrassing for Pivot and could have been catastrophic for Kerr.

At the same time people saying well Yeti's prototype didn't break. Yeti's prototype is way more finished than this one. Living in Arizona and seeing prototypes around this is a very early version.

I think both sides of the argument are looking way too much into this. It's a big deal for Pivot and Kerr and hopefully he is okay. But it doesn't really have an affect on the product we will be offered as the consumer.
  • 8 2
 @oldschool43: Ahhh, yeah, those metal-lugged / composite-tubed Trek bikes did have failures — but those were not Trek’s OCLV made-in-house full-composite frames with the 0.002” bondline pips...those were pre-OCLV frames that yes, were inferior. Those metal-lugged frames used table-rolled & shrink-wrapped carbon fiber tubes from MacLean Quality Composites (if I remember correctly)...it was definitely a less ideal construction method & structual configuration than Trek’s later 1992-ish OCLV bikes (which are what got me into composites at age 12; at it was amazing to get to work with Trek in 2008-2010 to bring one of their composite technologies to the automotive market).

But not all composite-tubed lugged bikes broke — Colnago’s C40, with its carbon lugs and carbon tubes, is one of the most well-liked road bikes of all time (including by TdF champs such as Bradley Wiggins — he and I battled for a 63cm NOS 1994 Colnago C40 w/full Dura Ace on eBay...and yeah, he really wanted it, and he won it, haha). Still hoping to get a C40 at some point (especially as my 64cm full-6/4-Ti 1999 Colnago Oval Master Titanio former team bike is my favorite handing, and favorite ride-quality, road bike of all time...having not ridden a C40 yet =)
  • 1 0
 @WRCDH: Yikes! I am just happy that didn't happen at Hardline. Scary stuff. Glad BK is ok
  • 8 1
 @Azrocktester: If you mean circus clown, I’ll take that as a compliment =P. I definitely got some “is the circus in town?!” looks when I did a 5.7 mile wheelie around Greenlake in Seattle almost 2 times, weaving on my rear wheel between many excited & perlexed onlookers. To my surprise, no one seemed upset and everyone seemed to enjoy the spectacle, haha...I guess they could tell I was in total control and wasn’t going to harm anyone =)
  • 2 1
 @jostaudt: @jostaudt: the reality of prototyping looks different. There is always uncertainty thats the reason there are Prototypes thats why we test things. Processes are known yes but also difffenret every time you change a parameter which you do when designing something new. also things interfere which is hard to predict
  • 2 0
 @WRCDH: You lost me at Fahrenheit
  • 1 0
 @jostaudt: depends on how long you have been around bikes for seen this and the same on carbon alloy frames @fector-b is correct
  • 2 0
 @jostaudt: not sure why you’ve been downvoted! I agree
  • 2 0
 @blacktea: it says so in the article.
  • 2 1
 @WRCDH: good point about the top tube/bottom tube angles. I will take your word on the rest of it ;-)
  • 4 2
 First there was Oceangate, now we have Pivotgate

Luckily Kerr is fine, but can you imagine the lawsuits coming Pivot's way if these bikes made it out into the wild and someone got kebab'd by a toptube?
  • 3 0
 @Spark24: the lugged versions were never going into production
  • 1 0
 Very well put.
  • 1 0
 To everyone who replied... thank you, I didn't see that the article continued after the photo!
  • 3 6
 @jostaudt: no, it is a prototype. Racers and free riders beta test components and frames before it hit FAI and a full production run. This is how it’s ALWAYS been. Even for DoD programs this is a known risk for all the engineers and “customers” involved. No matter how much FEA you do, a simulation will NEVER equate a real world test.

And stop with your anti galvanic corrosion BS. Its titanium lugs bonded to carbon fiber tubes. Dynamic assembly break, EVERY design has a cyclical load. Meaning, you shake that shake weight enough times, it will break.

Please actually get a design and manufacturing job before you sprout non sense.
  • 4 0
 @kroozctrl: Definitely aluminium lugs mate not titanium like on an atherton.
  • 2 1
 @WRCDH: How'd you get the job at McLaren!? I'm a mechanical engineer who's a McLaren fanboy at heart. Did you work on the tub for the P1? (my favorite car all time)
  • 2 1
 @WillW123: i know a guy who says if you say something authoratively enough to fool people you are 99 percent there
  • 1 0
 @HardtailHerold: exactly Smile ))
  • 5 0
 @WRCDH: this consulting is worth alot of $$$. they should pay/hire you.
  • 5 0
 @eastonsmith: Could be! I’m personally guessing that they machined the parallel-draw top/down-tube headtube lug because they likely used a 3-axis CNC machine...and they could machine both lug/tube bores in a single operation. Boring two different tube angles would require either another fixture / setup on a 3-axis machine, or it would require a 4 or 5 axis machine to do in a single operation/setup (like Hope frequently does for its complex parts like brake master cylinders).
  • 16 1
 @11six: The McLaren work is a bit of a long story, but if you like wild stories and McLaren, you might enjoy reading it =P. I’ve copied it below, and the same thing is also posted here: www.pinkbike.com/news/final-randoms-core-bike-2024.html
Oh, we did a lot of the engineering, R&D, and prototyping work in Seattle, and some at our facility in Andover UK, but I went to the McLaren Technology Centre in Woking a lot — all from 2005-2010. Then I did some additional McLaren Applied Technologies projects for several years.

As for the carbon tub, we backed out of producing the tub/chassis for McLaren and Carbotech in Austria took over when we didn’t want to take on the financial risk associated with McLaren’s quite-optimistic sales projections. Apparently Carbotech was almost sunk because of that issue (specifically, the lower cash flow from lower volumes in the first years made it difficult to recoup their investment and difficult to cover high overheard costs associated with the program). That’s one reason why McLaren moved production in-house to their new(ish) custom-built Sheffield facility a few years ago. The “patented” 4-hour “single piece” manufacturing was my contribution =). It’s actually a lot more than 4 hours — it’s just a 4-hour mold utilization cycle...with dozens of hours of other labor prior to, and after, that 4-hour mold cycle time.

The crazy thing is, I was supposed to be a summer manufacturing intern on the McLaren SLR in 2005 — it took about 9 months to arrange the internship with McLaren, being from the US. But then I broke my back snowboarding and had a spinal cord injury, a few months before the internship was due to start. I called McLaren’s HR manager from the hospital and she told me I was SOL — the internship wouldn’t happen due to my required recovery time. I was crushed. I didn’t know what to do if think, nor did I know if I was going to be able to walk, so I simply prayed for an opportunity to work with McLaren in the future. Amazingly, that put me at peace about it.

A few days later my friend Nichole visited me in the hospital...super cool and smart gal who loved cars and had a rad VR6 GTI. We got to be better friends during my recovery, and one day a few months later she told me her dad does aerospace composites, kind of like the automotive composites I was keen on, and that I should meet him. When I met him, he offered me a tour of their Seattle aerospace composites facility. A few weeks later the tour day was approaching and his engineering manager called me and told me to bring my resumé. I was stunned — my medical insurance had changed and I was going to no longer be receiving medical coverage in a few months, and at the time I wouldn’t be able to get new independent medical insurance due to my “preexisting” spinal cord injury (a rule which changed with Obamacare). But the tour went well, they liked my resumé, and they hired me a few weeks later — and I got full medical coverage, despite my “preexisting” (and expensive) SCI.

But 8 weeks after starting at that aerospace company, the sales manager called me to his office to discuss new market opportunities like nanocellular foams + composite skins, and single-crystal sapphire bulletproof armor windows with bulletproof composite doors for military vehicles. But when I was waiting outside his office, I heard him on a phone call discussing “McLaren.” I was mystified. When the call ended, he called me into his office and I asked about “McLaren.” He said “Oh no, you don’t know these people, they’re in England.” And I said, “No, I do know them, I was supposed to be working there as a college intern right now!” He was just as surprised as I was. Turns out McLaren had come knocking on our door (well, through the phone), as our company’s UK site made the carbon fiber fabrics and flat-pack CNC-knife-cut carbon fiber preform kits for the McLaren SLR program. McLaren wanted us to bid on their new car program...the program for engineering and prototyping and manufacturing the carbon tub for their next vehicle (just like is used on all McLarens today!). It was a 5-year R&D + Prototyping program, and then a $250,000,000 multi-year manufacturing contract =o ! We were all amazed by the situation — they had hired me to help them get into new markets, but they didn’t expect a perfect fit like this!

Two weeks after that, I was at McLaren Technology Centre bear London giving a sales / technical / business proposal presentation with our team, to the senior engineering & business leadership of McLaren — and after talking all lunch with their otherwise-reportedly-mute engineering director (where we accidentally invented McLaren’s hydraulically-controlled suspension-roll-control-system based on my similar Formula SAE system), we ended up being awarded the R&D contract! I couldn’t believe it.

The next day, we went to the McLaren SLR production facility in Portsmouth. While there, the manufacturing engineer who was supposed to be my internship mentor told me that the HR manager, Lynne, was in the office. We both realized we had to go talk to her, as just a few months earlier, she had to end my internship...all while I laid in the hospital, unable to walk. I walked in, Graham was smiling, and I introduced myself and Lynne had a look on her face like: “I told you no months ago, and I’m not changing my mind, I don’t care how far you flew to talk to me.” But then I told her that McLaren came knocking on our door in Seattle and that I was going to be the lead R&D engineer on manufacturing their next new McLaren carbon fiber vehicle structure. She couldn’t get her head around it. It made no sense to hear. Graham was just laughing at the stupefied, perplexed, almost-alarmed look on her face. She asked how this could have possibly happened. I told her I didn’t know, other than that I had prayed for an opportunity to work with McLaren, moments after I had last talked to her, when the internship fell through. None of us had ever experienced anything like that before, so we all just talked through it a bit...it was a fun conversation =). But she was just amazed that I was supposed to be a lowly production intern, making SLR’s all day for minimal pay, and now I was in charge of development their next carbon fiber car structure that would replace their SLR and replace their Portsmouth facility. It still doesn’t make sense to me today, aside from a direct answer to prayer in a crazy semi-miraculous way...including learning to walk again just months before! But yeah, I’m still waiting on that McLaren 720S in British Racing Green prayer =P
  • 7 0
 @WRCDH: This was a wonderful read. I'm glad things worked out for you.
  • 2 0
 @kusanagi72: Haha, no kidding. Fascinating and impressive analysis by @WRCDH but I must say I was temporarily distracted by the "optimal 0.002” thick bondline" (0.0508 mm). I managed to recover though and finished the read without getting lost at Fahrenheit Smile
  • 3 2
 @WRCDH: Are you Brian O rourke? He was the guy who did all of the Mercedes SLR Roof , Prior he was out at Lockheed working of low observables this was around 1998 I worked at Mclaren and know a lot of the people there to this day having been at Woking since the early days of the F1 cars and the new production facility A lot of people played parts in fixing mistakes made by people like yourself
  • 3 0
 @thewanderingtramp: This may be the craziest non-Waki PB comment thread in recent memory. Please carry on, chaps....
  • 1 0
 @thewanderingtramp: Whoa, no, but Brian sounds like he followed the same career path as me, maybe 10 years prior to me...I’ve gotta connect with him! In fact, I was the “technical lead” on manufacturing the full-size low-observable “radar pole model” of the F35 that was tested by Lockheed, as well as the F35 engine test ducts, and I have been out to Lockheed Skunkworks several times for other stuff (materials, machines, manufacturing, etc). I’ve also gotta get back out to MTC and drum up some new work and projects — MTC was my favorite place on earth during the 2005-2015 era =). Send me a message (or I’ll do the same soon), and we can follow up!
  • 2 0
 @suspended-flesh: I'm so fn invested
  • 1 0
 @WRCDH: Better hurry up. I hear Geely may be in talks to acquire McLaren. I doubt much will get outsourced to the US after that acquisition.

It's a shame that the McLaren brand has been so mismanaged. Build quality issues aside, the cars are on a different planet to anything from Maranello etc.
  • 1 0
 @WRCDH: you nailed it on the head either there.
The Atherton’s have it dialled.
  • 1 0
 @TokenCanfieldGuy: I’m curious, what creates hate against a bike brand? Hate is a strong emotion and takes effort. Dislike, sure. Hate, bit weird…
  • 1 1
 @rokboy: complete lack of emotional intelligence?
  • 6 0
 @tacklingdummy: I saw the frame up close and may or may not have pics of it up close.
The aluminium lugs are 1mm thick at best and have literally torn apart.
FAR too thin to be safe in my opinion as a fabricator. (admittedly im not an engineer so take that as you will)
It looks as though the lugs tore apart as a result of the bottom tube coming out of the lug and putting all the downward pressure onto the top tube.
  • 4 0
 @tacklingdummy: the Atherton lugs are also about 5mm thick so a lot stronger,
  • 2 1
 @rokboy: Risked BK-sports like by 'fabricating' a bike with that many (likely) flaws...catastrophically failed at the highest level. Unacceptable. Especially considering how flagrantly the bike was engineered^^^^read everything above if you haven't already for clarification on why Pivot bike is pretty junky when it comes to real deal integrity. Risked that dudes life for a pretty trash engineered design. The compressive 90* bend at the downtube lug alone is garbage (for carbon). It makes me dislike a company that would even think to release something that dangerous. even as a prototype, in modern-era 2024.
  • 1 0
 @Dodgysam: So, there is more to the story. There are definitely more questions now. It will be interesting if they release anymore information after fully investigating the broken frame. I'm sure the Atherton lugs are quite strong being titanium and thicker.
  • 2 3
 @TokenCanfieldGuy: what do you mean by release? You realized that was 100% prototype test mule don't you? Bernard shreds bikes hard and he's been riding pivot for quite some time. And it sucks? Yes it did. However, that bike was never meant to be released to the public.
  • 111 7
 Top tier response from Chris honestly! No tip toeing around and right to the point on reason, solution and mitigation. You love to see it. Happy BK is okay too of course
  • 15 0
 I agree. It is good to see brands being honest about things like this.
  • 1 9
flag tomo12377 FL (Mar 19, 2024 at 0:57) (Below Threshold)
 @lewiscraik: and their between a rock and hard place on this.. if they do the above and be honest they get hate and if they lie giving some BS excuse they get hate.. can’t win
  • 13 1
 @tomo12377: nah. If they lie/BS they will lose everyone's respect. But if they own it they'll only lose the respect of a few. It's a really simple decision Smile
  • 4 0
 Yes I’m glad he debunked that they want frames to fail.
  • 57 3
 Nobody is going to mention how well pivot have handled this situation? I for one dig the transparency
  • 19 0
 Cocalis has never been one to shy away from the hard lessons
  • 36 0
 Honestly. In my experience not a lot of brands would respond with this level of openness. Really nice to see.
  • 7 0
 I live in Phoenix and see Chris Cocalis on the trails at least weekly. Solid guy. He even helped me sort out a non Pivot bike I was having trouble with.
  • 38 0
 Little JB Weld onto 'er by'jaysus B'ys... She'll Buff!
  • 36 2
 I would much rather a bike from a company that develops at this level and takes accountability than one that doesn’t. Glad Kerr wasn’t seriously injured.
  • 3 59
flag TokenCanfieldGuy (Mar 18, 2024 at 23:32) (Below Threshold)
 Pivot bikes have been BIG trash as the years go by.
  • 1 0
 It's Kerr saving lives right there as they're recalling the rest of the batch. Not sure how many other testers could take such a full face smasher, eh...
  • 35 2
 Maybe the frame was Kerrsed?
  • 6 6
 That's quite a Burnard...
  • 17 1
 Obviously it broke because it didn't have internal cable routing to hold the frame together
  • 17 0
 The name's bond. Unbond.
  • 12 2
 Wow! Could’ve been a lot worse! I have faith in Pivot getting the PR nightmare sorted! As a pivot rider for the last 4 years I’ve only got great things to say about my Firebird. And as another commenter says Bernard’s bike gets more abuse than us mere mortals could ever throw at a bike. Glad Bernard’s ok. Gonna have to go scope his race day footage now!
  • 2 0
 yeah, I think it was bman right above you who mentioned about Bernard's bike getting more abuse from him vs mere mortals
  • 9 1
 I would like to hear more explanation of how/why the treatment failed to keep the aluminum in a state to keep an epoxy bond. Also, I wish someone would explain the benefit of the lugs and tubes sorta Atherton esque design that people are using now. Specialized and Pivot (and more?). What are the benefits that can't be achieved with a standard alloy mule or full carbon construction?
  • 29 0
 Ease of modifying the design. If through testing they need to switch up the kinematics or geometry, they can quickly machine new lugs to make these adjustments. Carbon tooling for a frame is very pricey, as well as tube molds for alloy bikes.
  • 4 0
 It's a balance of cost and performance, but mostly because you can modify geometry easily between versions. Hence proto frames and Atherton, whose bikes are all unique geo for the rider. The flexibility to adjust a prototypes geometry in the machined aluminum components (or printed Ti for Atherton) without having to redo a carbon frame layup plan is why. Easier geometry adjustments.
  • 9 0
 There was an interview with Chris somewhere… he talked about using this lug method only for rapid prototyping. Once they’re done tweaking the frame, they’ll build a full carbon version for sale. Also said it wasn’t feasible as these bikes would cost something like $20k each including all the man hours etc.
  • 27 0
 There are two major differences between the Atherton lugs and the Pivot prototypes lugs, material and bonding surfaces. The Atherton lugs are made with 3d printed titanium, which doesn't cause galvanic corrosion, and they have two surfaces for bonding, the carbon tubes slip into a slot so that they have ti on either side and are bonded on either side. This allows Atherton to quickly produce bikes that are at least semi custom, as well as reducing material waste. The pivot lugs are aluminum, cnc machined, and the carbon tubes are only bonded on one side. They are doing this specifically for developing the bike, easy to make quick changes to geometry, and the production version will be full carbon, like others have said. Pivots QC is usually immaculate, so this was a very rare mistake on their part, and they are doing the right thing to protect their riders who are on the proto frames.
  • 2 0
 @Dorkin: ah so its really the LUGS that are the benefit here. and the carbon is just the preferred tubing to keep the weight down... is this just an advanced version of alloy mules? as I can't imagine the lugs are being re-used change to change? both are just being done up in a jig i assume.
  • 10 0
 The way the Atherton frame are made is actually really smart. It reduces the amount of non automated labor that they need, so they don't need to hire as many people, and can make the bikes in their own factory in the UK instead of outsourcing it overseas. Given the Athertons investment in Dyfy, and the town that's there, it makes a lot of sense for them to make them that way, in addition to the customization that they can do on the frames.
  • 2 3
 @lepigpen: it takes a lot fewer man hours to machine an aluminum lug than it takes to weld an aluminum frame, and while molds for full bike frames are very expensive, you can 3d print carbon fiber in the more simple tube shapes. It saves a lot of time, and when you are prototyping, the time it takes between iterations is super important.
  • 5 4
 Discussions among my riding group are saying that Atherton bikes suffer from the same issue than the Pivot prototype. Not sure if true and how many cases of front end separation there have been for Atherton bikes. For sure one happened last year at a local DH race. This kind of reminds me of late 90s thermoplastic frames that were often lugged as well and also ended up separating. Maybe this type of construction is not meant to be ?
  • 4 0
 @Balgaroth: Only time will tell, Neko Mulally is going to start using the same construction as the Pivots for the Frameworks bikes if I remember correctly, so we'll have three teams on bikes with lugged and bonded carbon frames in WC DH, so we'll have a good picture of the long term viability. I don't think Aluminum lugs is the way forwards for consumer production bikes, but Ti has a lot of promise. I wonder if having locking lugs on the carbon tubing would help reduce the chance of them pulling out if the bonding happens to fail, similar to how a bolt on a rifle locks into the barrel. Food for thought. Manufacturing and materials science has come a long way since the 90s too, so that probably helps.
  • 4 0
 @eae903: one of the problems with a bonded jount is that it’s far more difficult to inspect te final quality without actually destroying the frame (cutting it up) than it is with welding.
You can inspect welds after testing for your QC, with bonding you basically do statistical spot checks (I assume on bikes also the welds checked are only a small percentage).
  • 6 2
 @eae903: probably not the best day for Atherton to be releasing their cheaper model with CNC aluminium lugs.
  • 2 0
 @eae903: Yes to the locking lugs. I've played around with bonded aluminium and carbon quite a bit and I really think that a mechanical connection is the only safe way to do it. If you shape the joint with some large scale texture (like > 3mm) and lay up the carbon directly onto it then you can the fibres shaped to really hold the aluminium. This way even if the bonding fails you'll just get a very creaky frame that won't break right away. With a lugged joint and premade carbon tube I think the only way to achieve the same failsafe would be to pin the joint as well as bond it. Alternatively, use premade carbon tubes with carbon lugs à la Calfee.
  • 1 1
 I think one more advantage of lugs with carbon tubes is that the carbon is primarily an advantage if you have a consistent and simple load path. Where tubes join and especially when you have bearings for bb, suspension components, fork etc the load path is so complex that an isotropic material (so a material which has identical properties in all directions) is often the lighter and more simple choice.

Does Pivot also work with double shear lap joints like Atherton/Robotbike uses? These lugs look machined so I suppose it would be too hard to do. The primary reason for using that is to avoid delamination at the free edge (where the tube got trimmed) but it may also give some redundancy as the tube is bonded both on the in- as well as the outside. They have a small hole on the outside for air and later the excess glue to evacuate so at least they know the glue is everywhere. So yeah, that's the check they can do. But I don't think they can actually check whether the glue has properly bonded to the metal. That said, I know that they have the Fokker Bond Tester (a resonance test) for checking glued connection in aviation but that's for body panels. Not sure whether it could be used for relatively compact machined parts.

Either way, failures like these are scary and I'm happy that Bernard came off relatively ok. Back in the days we built a car for a race in Australia where we built the suspension linkage out of pulltruded carbon tubes bonded to aluminum connectors glued to the inside (which were then connected to the bearings). During a test drive on Arnhem Highway (in Arnhem land, just east of Darwin) one of those glued connections failed causing a crash that could have ended much, much worse.

So yeah, carbon production has come a long way but it is still far from perfect. Remember though that head tube failures on aluminum frames used to be quite common whereas I haven't heard of (m)any in the past few years. Frames like these will get there someday as well.
  • 4 1
 @eae903: Yeah I think people forget Athertons didnt innovate their technique, they bought out Robot Bike Co. who had been working on these specific methods for years.
  • 2 0
 @eae903: not sure having WC teams using the tech will be of any use to assess whether this method is reliable or not. A prime example is Commencal, we never saw any frames explode with the WC teams, but at the consumer level the info came out that the Suprems have a lifespan shorter than a fruit fly. The only hope with this is Neko since he was really open with the development of his frames Tho now that he sells frames, by nature he became a bike brand and saying that stuff explodes is not a recipe for commercial success.
  • 2 1
 @lewiscraik: I think they’ll be fine. The reason the Pivot failed is not an issue on the Atherton bikes, which don’t use carbon and alu together.
  • 3 0
 @lewiscraik: "Lugs are manufactured using a re-imagined CNC process and both lugs and tubes are made from Aluminium 7075"
Sure they have it nailed.
  • 1 0
 @WillW123: Pole uses same kind of aluminium and adhesive in their Finnish made frames. Tried and tested method.
  • 2 1
 @kiisseli: One thing Pole can do which these tube-in-lug companies can't is to clamp the glued surfaces together as it cures. Not sure how much it matters for the glue they're using but for some glues obviously clamping is essential for a good bond.
  • 1 0
 @lewiscraik: Wonder how a stainless steel lug would hold up
  • 3 0
 @lewiscraik: Shouldn't be a problem, since it's also got aluminum tubes. There shouldn't be galvanic corossion as far as I am aware.
  • 4 0
 So if I may explain from an adjacent technical background (not an engineer).

Etching cleans and roughens the surface, this essentially gives the material something to stick to, everything bonds better with some profile, some porousness and aluminum is not a very porous metal.

From experience in the coating industry aluminum and galvanized are hard to coat and require a ton of prep and specific products to provide a long life.

When they say etching failed, you can use a mechanical etch like lasers, or a chemical etch like muriatic acid. either the mechanical or chemical etch was insufficient to provide a profile to bond to.

Many products struggle with bonding issues, personally the raceface next sl cranks came to mind as the insets suffered multiple bonding issues and ultimately a recall on production products.
  • 12 0
 That's a better answer than pole gave...
  • 7 0
 Interesting comparo between Carbon/Titanium and Carbon/Aluminum galvanic corrosion....seems Atherton is essentially immune to galvanic corrosion issues, while aluminum bonded frames are always perilously close to galvanic corrosion problems.... Aluminum Coupled to Carbon Composite: Aluminum alloys are extremely vulnerable when they are coupled to a carbon composite. During the galvanic corrosion, a white, jelly corrosion product will be formed on the surface of the aluminum. There is an assertion that the galvanic corrosion rate of aluminum could be mitigated by the anodization of aluminum and the formation of a thick, protective aluminum oxide layer on the surface. However, it has to be mentioned that in the case of a breach of the oxide layer by mechanical damage, the situation becomes much worse due to a really high cathode-to-anode surface area ratio (Ac/Aa)

Titanium: By looking at the standard electrochemical potential of titanium, it seems that this metal is an active metal. However because of the formation of a dense stable and protective oxide layer, titanium is placed among the noble materials and just below graphite or carbon in the galvanic series table. (For a primer, see the article An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion). Therefore, there is no significant gap between titanium and carbon-fiber-reinforced composite to create galvanic corrosion. This means that commercially pure titanium and its alloys are completely resistant to galvanic corrosion when they are coupled with carbon composites.

  • 2 0
 wow seems like steel would have faired no better! very interesting read for sure!
  • 3 0
 @mariomtblt: had no idea how galvanic corrosion can ruin a person's day
  • 2 0
 @jokermtb: Ask any old Land Rover owners Big Grin
  • 6 0
 When BK was losing time on his final Crankworks DH run, it was odd as he was riding so hard - the time loss didn't jell with how fast he was riding. I'm merely guessing that perhaps one tube's epoxy had already let go of the lug, and the other one was still holding, but BK was being affected by the diminishing handling capabilities that would be hard to identify during a flat-out dh run. A soggy front end would definately affect the pop needed for the last triple, and may have contributed to casing it - an impact that was enough to pop the remaining epoxy loose and the crash everyone can't soon forget. Glad BK just started wearing that Leatt chest protector, as he fell hard on his chest and face. He definitely use one of his 9 lives on that one....can you imagine if this had happened during Hardline!?!?!?!? He's kinda lucky in a weird way. Glad BK is unscathed for the most part......I'm glad that Chris C. at Pivot was able to add a bit of context to what happened, and is on the path to figure out how to improve the techniques to make such a frame.
  • 3 0
 I agree watching the run on BK's channel , I saw the same struggles as you did.
  • 19 11
 So we can talk about this but we can't talk about Thibaut daprela?
  • 1 0
 I suspect there is still a case pending. I’m sure the outcome will be published.
  • 5 0
 What happened with thibaut?
  • 7 0
 would a Brooklyn machine works have cracked under the same pressure?
  • 5 0
 The most important that BK came out from this nasty crush with only minor bruises. And hats off to Chris for being honest about the accident/problem.
  • 2 0
 "Nasty crush" sounds like a Freudian slip!
  • 3 0
 Less of a prototype frame failure and more of an adhesive bonding issue. Which may be the fatal flaw in this frame scenario. It takes some very specific chemical engineering to etch and bond 2 different types of materials. Especially when one is a polymer and the other is metallic. I had no idea 6061 or 7075 billet could even hold epoxy with integrity. Back to the drawing board or perhaps the round file. Best of luck, I love seeing all of the newer manufacturers techniques!
  • 5 0
 I was waiting for damage control. Hard Line and Taniwha are certainly good testing grounds, but not for BK.
  • 2 0
 Great to hear first and formost that Bernard is OK.
Great that Pivot is being so open, this is what it is all about.
Obviously didn’t want this to happen to anyone, but it is a perfect example of what can happen sand as Chris quite rightly points out Bernard’s bike had already been ridden super hard at hardline!

  • 3 1
 Everything fails at some point. All these Pro racers, slope and freeride riders break frames, wheels, etc, etc......Hell even the weekend warriors breaks a frame here and there. It's all part of the game especially with a case like that.
  • 3 1
 The exact same way all the epoxy lugged bikes of the 90's failed. You have your epoxy, still intact on a tube. Engineers:"In theory, you can hang a 50,000 pound weight to the end of the tube and it won't fail". Mountain bikers:"Hold my beer!". BTW, it wasn't just rowdy early 20's kids separating frames, it was old guys with feats of daring such as riding off a curb. At some point, it was "pass" on epoxy mixed material frames. Didn't work before, why would it now.
  • 3 1
 @winko: you are incorrect about the Boeing part being prototype. I've worked in the aviation industry for the past 24 years and also currently work at Boeing. NO part on an passenger aircraft that in in service with passengers aboard has a prototype component on it. Each and every part has to go through FAA regulatory service and prototyping prior to installation on commercial aircraft. The reason those aircraft crashed was due to lack of pilot training. When Boeing went to the 747 to the max, Boeing Failed to properly train the pilots on the new flight control system called SAS. Stability Augmentation System. That's what caused the aircraft to crash.
  • 4 2
 Doesn't help that BK and the PFR team transport their bikes in used cardboard bike boxes they literally duct tape together instead of proper bike bags. Not sure what's harder on a frame, Hardline or a n airport baggage handler lol.
  • 1 1
 I only own a proper bike travel box cuz I can afford one fancy bike. Otherwise, I would transport mine in a cartbox and not give a shit as well. It's a bike, it can take a beating.
  • 2 0
 Everyone saying frames shouldn’t break, it’s a disgrace, it’s negligence blah, blah, blah, need to look into the story how BK came to be associated with Pivot.

Basic synopsis is he snapped one of their down hill frames years ago, then when spoken to, said he knew what had caused it and could snap them on demand if they wanted him to, this led to the association and the development of improved frames….or something like that.

Frames shouldn’t break, cars shouldn’t crash and houses shouldn’t catch fire but they do.
  • 2 0
 Didn’t Chris Cocalis used to own a bike company that made full suspension titanium frames? Why the aluminum lugs? If galvanic corrosion is a known issue between aluminum and carbon fiber? Obviously there’s treatment to prevent that but according to some of the engineer’s comments it’s a high end lab grade process to do that. Why not simply make the lugs from titanium the way the Athertons do? Chris obviously knows titanium.
  • 2 0
 There is cell phone video from the side of the track and you can see the bike squirm a bit right after BK pumps the roller before going for the triple, then it looks like he doesn't give a full pull but just hangs on. My guess is the the frame started to separate right before the lip, which would be why he cased, with the frame then completely failing. BK can jump we all know that.
  • 5 0
 Rob called it.. truly a worst “case” scenario
Really glad BK is ok.
  • 2 0
Pivot shares, sales, confidence in products!!!

Bottom line is this particular bikes are getting pushed to a point/level that 99.9% will never get near! So confidence shouldnt be lost in Pivot frames
  • 4 0
 The fact that he hit a tree head on in practice probably didn’t help neither
  • 1 0
 this is a reality manufacturers face. Glad Kerr wasnt hurt, sometimes products are just pushed to their limit as a company figures out the best way to design and then product something. Even once things are dialed in there can be inconsistent batches where something just did not happen correctly. Nobody can predict this.
  • 1 0
 Ive see the same thing happen with the head tube pulling away from the main frame on production bikes from very big reputable companies. This after all is a prototype and one of the main reasons Kerr is so valuable to Pivot is he breaks everything....this is a valuable skill. Just very glad BK wasn't hurt and that it will not impact his WC season!!
  • 5 1
 I think we can be sure those snotty kids apparently INSTANTLY laughing at BK’s crash will never get a ride from Pivot.
  • 5 1
 This point was already addressed by someone who was standing with those kids - they were giggling at the fact they made it onto the big screen.
  • 1 1
 @o-dubhshlaine: weren't they a bunch of juniors/pros? I don't think I buy that, not a good look for future sponsorship.
  • 1 0
 Lol, that frame failure was the same as Sam Pilgrim's bamboo bike, how stupid was this, that joint is a weak point, their engineers know better at Pivot, change the design and have a better test prototype bikr for Bernard Kerr, cuz we know he doesn't hold back riding in races. Lol.
  • 3 0
 Just remember the real problem here is the lack of V12s and V10 in F1

  • 1 0
 I recall the same stuff happening with Vitus and Miyata bikes at my old shop 30+ years ago. They were high end, high spec rides back then and that carbon/glue/alloy connection was not a happy marriage for long. Of course materials, adhesives, preventative findings of dissimilar materials have been discovered or strengthened. But sorry every time I see carbon lugged bikes this is exactly what I expect to see. Horrors are hard to forget. Hopefully they will get the construction dialed in and most importantly glad that BK is alright.
  • 2 1
 The problem is, that lugged designs, (especially true when the lug and the tube are made out of different materials) are immanently prone to problems. The sheer amount of (design) parameters, that you need to control in such a connection, is a big issue. You need to take into account e.g.:
- different materials with their different thermal expansion coefficients creating relative movements and resulting in forces in all directions
- the different stiffness of the lug and the tube in the overlapping area due the material properties and the form factor (design) to prevent stress raisers in all areas and to minimise relative movment during deflection to reduce the shear inside of the adhesive film and in the connection faces between the adhesive/tube and adhesive/lug
- The manufacturability of the lug/ the tube. Not all shapes can be produced with the chosen process like the cnc milling of the lug and the carbon fiber tube lamination.
- The assembly order of the tubes, especially, when there is a radial overlapping between lug and tube. The last lug must be able to be assembled in one direction. Like already stated by WRCDH the tube directions at the Head Tube Lug should have different directions to allow for a form-fitting. Apparently the Pivot engineers have decided to use the head tube lug as the last bonded lug. This assembly order however prevents the desired form fitting in one of the most stressed areas of the frame. During a touch down after a jump, there are huge forces, that tend to pull the lug from the tubes - just have a look at the „hug to flat“ videos and the deflection of the fork stanchions in the driving direction! And obviously, this is the direction where the lug is completley reliing only on the adhesive connection working properly, there is no redundancy here, when the tubes and their assembly direction of the overlapping area of the tube and the lug is arranged in parallel and in the force direction like on the Pivot. The Pivot Enginners have tried to minimise the risk by incresing the size and the length to diameter ratio of this connection, which is obviously not enough.

As you can see, all of these design parameters are often contradictory and in fact even more often contradictory to the intended behaiviour of the whole system like the frame or the whole bicycle in the field (overall frame stiffness vs. connection stiffness of the lug, etc.).
This is quite challenging if its a design like a prototype dh bicycle, where the amount of financial investment, that you are able to put in is really limited and at the same time you have a vast amount of different and confusing influences from manufacturing (bonding surfaces preparation, curing temperature, correct adheasive bead thickness, al these parameters must be obtained by a huge number of repeatable experiments, inputs from the adhesive supplier, etc.), human behaviour and imperfections during the assembly - we are not robots allowing for 99 % of repeatability, a huge type of hardly predictable external impacts like different strains (e.g. multidirectional loads, temperature changes, etc.) - this data must in general be collected by data aquisition in relevant operating states and environments: e.g. on different tracks (min 3) with min. 3 different riders in advance of the design process.

During this process you need to execute comprehensive lab testing with your saples, taking into account the relevant load cases, This testing must show a sufficient life span, prior a testrider enters the bike.

Most important: at the end there must be a replicable „closed loop“ between all these Influences and Variables and your design of the product and your manufacturing and assembly process and the user instruction.

You need to be clear about the fact, that, as an engineer, you are responsible by law to control all these influences and even for a prototype (!) using all currently known and available methods of the so called state of the art, to prevent such a katastrophic failure like happened now.
Just the fact, that a lot of bicycle prototypes regulary fail, does not liberate you from these obligations. And if you are not able to prevent a failure by the design (over the entire lifespan and a reasonable amount of abuse by the user), the process control and all its parameters, the product design must be executed in such a way, that the failure is „anouncing“ itself for reasonable amount of time e.g. and amount by visual deformation, unusual and massive sounds etc. - and not happening instantly.

All these steps, measures and countless (design) desisions needs to be documented thorougly in these days. Even for a prototype! There is a chance that you will be forced to show and explain this documentation in detail in front of a judge, if something goes horrible wrong. You need to always keep this in mind as a responsible Engineer/ Engineering Manager or Managing director. But on the other hand, it should not prevent you from beeing innovative and find new solutions. Very often this is a hard fight in engineering departments, or between departments of product centered companies in general. This is not an easy Job.

What really astounds me is, how fast pivot has drawn its conclusion - thats seems to be to fast for my understanding.
From my point of view all these kind of frames should be immidiately taken out of operation, the analysis should be executed thorougly in house and in parallel by an accepted institution like an university or an independent testing laboratory. Based on these results - and only then, and after a thorougly process and design considaration and a comprehensive risk analysis, they should take and announce countermeasures. But maybe I am wrong and they have done all that…
  • 1 0
 Why Pivot decided to go with Aluminum lugs bonded to the carbon tubes is beyond me. Titanium scores very low on the galvanic scale when bonded to Carbon, why Atherton uses Titanium.

I don't care how much surface treatment you give the aluminum lugs, corrosion will happen.

But, BK and the rest of the pro's are "test pilots" of sorts, they are paid to push these materials to the brink. Looks like BK found this prototypes limit!
  • 1 0
 Had a “Thermoplastic” GT LTS in ~98ish that did that. Similar frame material and concept with 25 years since to perfect. I rode into a what I thought was a puddle and turned out to be fresh concrete that was 18” deep. City of Calgary answered to why there was no signage on the fresh concrete sidewalk.
  • 1 0
 In the message from Chris that they are investigating frames produced at the same time. Are there frames that have been produced at a different time? Did they change the process on those? If not will they recall those back? If they did change the process did, they suspect a problem? If so, why did they not recall that batch prior to a failure? My other question is why did they not build/machine the bend into the lug and keep the carbon downtube straight?
  • 1 0
 Why the hell use any kind of mixed material/bonding/lug type construction for such a critical purpose? Putting the rider's life on the line, for saving 500grams? I don't get it.
Why does the manufacturer even take this risk for potential negative impact on their reputation? I guess nobody did a 'what if...'
  • 5 1
 Gotta break some eggs if you want to make a omelet.
  • 3 3
 I wonder if you do simulate that impact scenario in a lab testing setup. You would have to pull at the front end to simulate this kind of failure. I think this is actually a design flaw in this prototype setup. You create a distinct shearplane, so when the force put in exceeds the bond strength of the carbon aluminum interface. So if it fails, chances are high it fails in a catastrophic manner. Yes, also fully carbon bikes snapped in a similar way, but also it's easy to be smart afterwards, this could have been expected.
  • 1 0
 @Happymtbfr: thanks for clarifying that. Didn't think they would do it like that. I thought it would be more like a press puting vertical loadcycles on the bottom bracket while the Axel are confined.
  • 1 0
 @styriabeef: Headtubes are under a lot more forces than just those introduced from BB loads.
  • 5 0
  • 5 1
 Thanks for spelling break properly.
  • 2 0
 Anyone saying crap about it breaking is MORONIC
It’s a prototype
And Has there ever been a production bike failure from all brands before?
  • 1 0
 I've been told by someone in the industry who wishes to remain nameless,

"Bernard likes the pies".

This is the real reason why his frame snapped but keep it between ourselves.
  • 1 1
 would like to be a fly on the wall of the Pivot meeting room. it seems that higher consequence mtb events, and theres a lot of them, put higher stresses on frames and wheels than events of 25+ years ago. so it stands to reason that the tech used to build a prototype should be taking these higher consequences into account. the pic of BK’ frame with aluminum lugs looks dated. didnt we have a whole slew of companies trying this tech way back when?
my guess is that all the boutique brands that wanna go to the big dances are paying attention to this incident
  • 1 0
 RnD is what pivot do best and they handled this well Professionally they are up there
  • 1 0
 That was a Hard Hit. Could have been nasty. Just glad that BK is ok. Just shows how hard the really push it and what shape these athletes are in.
  • 3 1
 I guess the same wouldn’t happen with an Atherton frame? No galvanic corrosion with titanium?
  • 4 0
 Aluminum Coupled to Carbon Composite: Aluminum alloys are extremely vulnerable when they are coupled to a carbon composite. During the galvanic corrosion, a white, jelly corrosion product will be formed on the surface of the aluminum. There is an assertion that the galvanic corrosion rate of aluminum could be mitigated by the anodization of aluminum and the formation of a thick, protective aluminum oxide layer on the surface. However, it has to be mentioned that in the case of a breach of the oxide layer by mechanical damage, the situation becomes much worse due to a really high cathode-to-anode surface area ratio (Ac/Aa)

Titanium: By looking at the standard electrochemical potential of titanium, it seems that this metal is an active metal. However because of the formation of a dense stable and protective oxide layer, titanium is placed among the noble materials and just below graphite or carbon in the galvanic series table. (For a primer, see the article An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion). Therefore, there is no significant gap between titanium and carbon-fiber-reinforced composite to create galvanic corrosion. This means that commercially pure titanium and its alloys are completely resistant to galvanic corrosion when they are coupled with carbon composites.
  • 2 2
 After this and that wheel failure at Hardline, it must surely effect even an athlete like BK from a confidence point of view, nevermind physically. They truly are made differently...
  • 5 0
 They should make the frame out of whatever he's made from
  • 3 1
 Gee's bike, of similar construction, appeared to fail in the same way when he had the big off on the ridge line.
  • 1 0
 His bike didn't fail. It was still in one piece after that.
  • 3 0
 @CaptainJulian: from around 10 secs you can clearly see the headstock detaches:


What's odd is that it takes a bunch of hits, then right at the end as it's coming to a stop it separates into 2.
  • 3 1
 @AdmiralHazzar:Sorry I thought you meant Rampage, Haha, he has too many big offs.
  • 1 0
 So that means BK was riding this framewith the carbon tubes not glued to the lugs at all?

Glad this thing didnt get pulled apart at hardline then Big Grin
  • 3 0
 Casing a massive triple...something is gonna give
  • 1 0
 BTW there was a 'contract failure' we haven't heard about in PB... and damaging/speculations keeps going bigger and bigger...
  • 2 0
 It’s really nice to see a company be open and upfront about a failure rather than be all secretive about it.
  • 1 0
 Looking on the race roundup photo’s, there was one of someone holding a totally snapped carbon frame - no-one is even mentioning that!
  • 1 0
 based on these comments I feel like this was a great marketing move by Pivot... Kerr is ok, and everyone talks about Pivot and how they "owned" it Big Grin
  • 1 0
 Use a nonconductive interface layer like fiberglass. This is done in carbon to aluminum bonding for aerospace applications often.
  • 1 0
 The ghost of Vitus returns! Not knowing and understanding history will lead you to repeat lessons from the past. The GT lts carbon was built how it was for this reason.
  • 1 0
 hum... crank brothers all over again. in history bonding metal parts have been a no go for me from my experience of crank brothers. this is just a reminder.
  • 3 3
 I wander if you sucked the air out of the frame if the vacuum would hold it together? Assuming a vacuum could be sustained over time
  • 12 0
 But on impact then the frame would implode and suck the rider into a different time continuum / event horizon.

On a serious note, cable routing may be an issue then…
  • 1 1
 you volunteering for the suckin'?
  • 1 0
 Could call the frame the Titan
True about the cable routing! Surely there’s a way of keeping the down tube in compression? @rich-2000:
  • 1 0
 No, it would only add 14.7 psi of tube cross section at the bond. Good epoxy joints can handle 4000+ psi across the bonded area.

So maybe 60-100 lbs of suction force, vs easily 20,000+ lbs of bond strength.
  • 5 4
 Who cares about the frame. FL Badge? Also, glad Kerr isn't hurt. Prototypes break. This is not news.
  • 1 0
 They are "ready for the full impact of another World Cup season"
Wasn't one enough?
  • 2 0
 I would be binning the frame after hardline!
  • 1 0
 First they can for your headset tourism, then they came for your headtube tourism.
  • 2 0
 Where is @Compositepro when we need them?
  • 1 0
 Hes dead
  • 2 0
 Remember boralyn? Shattering stuff!
  • 1 0
 Pivot Cyles
Prototype 1: Include head tube pivot
Prototype 2: Don’t include head tube pivot
  • 2 0
 BK body May have survived but what about his confidence in those frames?
  • 2 0
 "Trust me, I'm an engineer"
  • 2 0
 Reminds me of the titanic submarine…
  • 2 0
 Why the people at 01:53:30 are laughing ...... bruh
  • 1 0
 If it can happen to Pivot it can happen to anybody, they are well known for their top quality design and fit and finish.
  • 1 0
 Looking at the Atherton 170 bike. They really reinforced the headtube/top and headtube joint. Pivot should take note.
  • 2 0
 Time for RE500
  • 3 1
 Looks like a GT Lobo.
  • 1 1
 On effort to pivot outa reach got striked fanged by tiger snake at Maydena hardline....
  • 2 0
  • 1 0
 Like a UNI bmx seat... sooner or later the glue lets loose
  • 1 0
 It’s been a rough year for carbon tubes bonded to metal.
  • 1 0
 Yikes Eek
  • 1 0
 Crash Test Bernie!
  • 1 1
 12mm grub screw instead instead of epoxy - Problem solved
  • 1 1
 would have sheared instantly.....
  • 3 3
 Ew glued bikes are just as bad as cable tourism
  • 1 4
 That bend in the DT where it meets the Head tube? makes me think there's not enough insertion connection for the prit stick to bond?
  • 2 0
 no one will ever be able to accuse mtn bikers of listening to good music, except for the guy who posted an opening day video from buffalo creek...
  • 1 0
 @c1olin: Its whistler from ROAM...
  • 1 2
 looks like a friday fail
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