Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
PINKBIKE FIELD TEST
Rocky Mountain Slayer Carbon 90
Words by Mike Kazimer, photography by Trevor Lyden
Rocky Mountain Slayer Carbon 90
Words by Mike Kazimer, photography by Trevor Lyden
The Rocky Mountain Slayer has gone through several transformations over the years, but the 2020 model has its sights set squarely on big mountain riding. Not surprisingly, it's longer and slacker than the previous edition, and there's now a version with 29” wheels that has 170mm of front and rear travel, while the 27.5” option has 180mm of travel.
Along with the two different wheelsize options, the Slayer is available with either a carbon front triangle and an aluminum swingarm, or a full aluminum frame. All of the frames have Rocky's Ride-4 adjustment system, a flip chip located at the rear shock mount that allows for, you guessed it, four different geometry settings. Most of the testing took place with our size large bike in position 2, which gives it a 64.1-degree head tube angle, 76.1-degree seat tube angle, and a 471mm reach.
Slayer Carbon 90 Details
• Travel: 170mm rear / 170mm fork
• Carbon front triangle / aluminum swingarm
• Wheel size: 29"
• Head Angle: 63.8° - 64.8° (geometry)
• Seat Tube Angle: 75.8° - 76.8°
• Chainstay Length: 442 / 440mm
• Sizes: M, L (test), XL
• Weight: 33.2 lbs (as tested)
• Price: $7,999 USD
• www.bikes.com
• Travel: 170mm rear / 170mm fork
• Carbon front triangle / aluminum swingarm
• Wheel size: 29"
• Head Angle: 63.8° - 64.8° (geometry)
• Seat Tube Angle: 75.8° - 76.8°
• Chainstay Length: 442 / 440mm
• Sizes: M, L (test), XL
• Weight: 33.2 lbs (as tested)
• Price: $7,999 USD
• www.bikes.com
Our test bike was the 29”-wheeled Carbon 90, which is spec'd with a 170mm Fox 36 Factory fork, DHX2 coil shock, Shimano XTR drivetrain and brakes, and Race Face ARC 30 rims laced to DT Swiss 350 hubs. All that adds up to a retail price of $7,999 USD.
Yes, there's an elephant in the room, but let's take a moment to briefly go over how the Slayer performed before testing was abruptly cut short.
Climbing
The Slayer was designed with descending in mind, but the seated climbing position is comfortable enough that skipping the shuttle truck and pedaling back up to the top every so often is completely feasible.
It has a steep actual and effective seat tube angle, which means that even when the dropper post is fully extended the seat doesn't end up too far behind the bottom bracket. That centered position, combined with chainstays that never felt too long or too short helps make the Slayer a competent climber, although it doesn't feel as efficient as the Yeti SB165 or the Specialized Enduro. That's where the climb switch on the DHX2 coil shock comes in handy – a turn of the blue lever is all it takes to calm the back end down for those longer logging road grinds.
The Slayer can be run with a coil or air shock, and there are multiple possible geometry settings thanks to the Ride-4 flip chip at the rear shock mount.
Rocky's own 'Spirit Guide' helps ensure the chain stays where it belongs.
Descending
For a bike with 170mm of travel and 29” wheels the Slayer was surprisingly nimble; there was an unexpected level of liveliness that allowed it to remain enjoyable on tighter, slower speed sections of trail. It did well on the higher speed straightaways, too, although it's not quite stable and planted enough to earn it the mini-DH buzzword - it feels more like an enduro bike with a little extra travel.
There were a couple of instances on steeper section of trail where the front center felt a little short, despite the fact that the 470mm reach isn't out of the ordinary for a bike like this. It's possible that going with a slightly longer stem could have resolved this, but unfortunately we didn't get the chance to experiment. Moderate hits were handled well (except for one...), with enough ramp up to prevent any harshness at the end of the stroke.
It Broke
The Pinkbike Field Test isn't meant to be a test of long term durability; instead, the intention is to get a solid grasp on a bike's handling and component performance over the course of a few weeks of riding. Unfortunately, we ended up finding the limit of the Slayer's strength during a warm-up lap down Whistler's famous A-Line trail.
Disaster struck on the third to last jump. Test rider Luca Cometti hit the jump the same way he had on multiple bikes before, landing a little deep but with plenty of transition left, only to have the back end of the bike break on impact and toss him to the ground on the side of the trail. A trip to the clinic was in order, and while he was lucky to escape more major injuries, he did break a couple of ribs and sustained enough bruising that his time at the Field Test was over. Not good.
This Rocky-branded axle is used across much of their range.
Our current theory is that the axle broke first, and then the resulting twisting force pulled the back of the chainstay apart.
What Exactly Happened?
We don't know. Our current working theory is that upon landing, the Rocky-branded axle snapped at the driveside threads, causing the wheel to twist and tear the non-driveside chainstay apart. We wondered if maybe an early sample of the alloy rear triangle didn’t get a proper heat treatment, but testing it for hardness showed that it measured within Rocky Mountain’s parameters, so that wasn't the problem. The axle itself was neither overtightened nor loose; we had a certified mechanic doing the tire swaps (for control tires) and re-installing the wheels on the bikes—so we know it wasn't Levy's huge guns that caused this.
To their credit, Rocky Mountain didn't give us the 'pre-production' excuse – the bike we had was a full production model. The Slayer also far exceeded all of Rocky's in-house and third-party testing before production, which made the failure we experienced even more surprising to them.
Rocky's position is that despite this failure, the Slayer is safe to ride. They issued the following statement:
 | Rocky Mountain’s team of athletes and engineers are passionate about mountain biking. We pursue an ongoing process of continuous improvement of our bikes. In this spirit, we’ve been studying the bike that Luca was riding and we’re looking for opportunities to make improvements to our manufacturing process, design, and fine-tune our already stringent testing process. This is to ensure the durability of our bikes and the safety of those who ride them. |
So is there simply not enough material around that cool looking blind pivot? Are other bikes from other brands out there time bombs just waiting for an axle failure that would cause them to tear apart like this? All the bike strength tests we know of assume the structural integrity of the axle, so that is certainly possible. We don't have those answers today.
We had high hopes for the Slayer, but because it broke during riding conditions that should have been well within the realm of its capabilities, we can't recommend it—for now. We hope the reasons for the failure become clearer, and Rocky Mountain can address any issues quickly. Once that happens, we'll give the Slayer another try.
Pros
+ More versatile than travel and geometry numbers suggest
+ Good traction in rough or loose terrain
+ Comfortable climbing position
Cons
- It doesn't have high-speed stability of some other bikes in this category
- It broke catastrophically
Author Info:
Must Read This Week
Sincerely yours Pinkbike Audience.
That was an axle for a shorter travel cross country prototype and never should have been sent out. Hee hee hee...Pole.
However, PB stated "Rocky's position is that despite this failure, the Slayer is safe to ride."
I'd like to hear directly from @RockyMountainBicycles that "the Slayer is safe to ride."
"I want to be bullshitted in a more skillful manner" instead of rather delusional "I want to hear the truth". delusiuonal because in reality nobody wins by learning the truth. In such cases attempt at telling the truth does more harm than good, it gets interpreted and spun off. Nobody wins. nobody.
Yes "when you are bullshitting me, I want you to make me feel good about it" - "it's not about the truth, it's about how your statement makes me feel" - philosophical but very interesting aspect of PR in my opinion.
So point being new bikes braking and almost getting us killed WTF?
Rather have the last iteration anyway, way better looking
The upper/lower rockers being carbon wouldn't worry me too much outside of maintenance (I prefer removal/installation of bearings on alloy to carbon), but those two smaller arms on the side seem like they should be burlier or made of another material, a few hard bottom outs and it seems easy to see how they'd be compromised. They are def. the weakest part of the link.
I've got a few weeks on my build with alloy links and I've done some pretty nasty rides, so far no issues. I wouldn't worry about pushing it.
We have all left something loose on our bikes and if anyone says they haven’t they are a liar !!!!
The point is RM is getting out in front of it and addressing it well. With some unknowns they are best to review and try to determine if any changes are necessary. I trust a brand like RM is making every effort in engineering & quality control.
I had one where I thankfully caught the crack well before the catastrophic failure that could have seriously hurt me on a Jekyll. They still called it crashed related and refused to honor the lifetime warranty even though the bike had never been crashed and their were no scratches etc.. The only blemishes were the paint chipping off around the cracks in the carbon due poor frame alignment/rotation (imagine taking a snickers bar and twisting it in opposite directions at both ends, the chocolate will start to crack, same thing happens with pain on a carbon frame, the carbon will ischemically crack along the fibers, the paint will crack more perpendicular to the carbon cracks).
And I'm an RM fanboy
Even if the truth is "we don't know" I'd rather hear the truth, wouldn't you?
Not sure if it's interesting or just an oversight on the article but they mention that the material of the chainstay was hardness tested, but didn't mention anything about the axle material?
I know you know everything but..there is my modest expert opinion
I know it's hard for folks to accept that the bike broke, but think of it this way: The rider, who could have been any one of us, was sent to the hospital because a brand new bike failed catastrophically.
Show me a similar failure, I don't think I've heard of an axle snapping, though it's hard to say whether the axle failed first or the frame failed first.
Its frightening following my 7 and 9yo's down there.. I'll leave jumps to the kids.
Worth noting there is a significant difference between riding your own bike and a one that you don't have a financial obligation towards. Not saying he rode it beyond its limits, but you land sideways on every a-line feature at the speeds Luca is clearly capable of and there's a reasonable chance somethings going pop... just like the kid who snapped that pole in the bikepark I suppose.
I bet if you really tried, you could break every single bike in the entire test lineup.
@BoneDog: Sure, but brand new bikes?
@DH-Angel: Exactly. If testing can't find or repro the issue, either:
A) testing/QA isn't sufficiently rigorous, or
B. Mfg tolerances are too large.
I agree that dropout looks an urban primal earhole earring that went too large too fast. Get more material there stat!
@BoneDog: I've worked with 100+ vehicle fleets. Dodge & Ford. Recalls coming in all the time.
Brand new vehicle fails, breaking the ribs of the driver? Not even, man.
That's front page news.
Don't normalize this terrible behavior.
RM should take a page from other companies with integrity & issue a recall.
I think that the hub was machined slightly to big for the axle which caused uneven vibration and force on the threaded bit. This could make it a issue on specific builds from select production runs. Regardless of what I think happened rocky should be able to find out why the failure happened and inform their dealers and customers to prevent further failures.
Safety should be rocky's first priority and for them to say that this is a full production bike but it wont happen to other bikes with out giving any explanation to what happened shows their ignorance of the problem and leaves their customers vulnerable to more injury and failure. At least Pole found the reason for their failure and fixed it even if the way they did it was a PR nightmare.
I would disagree I'm sorry I'm just older and wiser. Just because you run a machine shop doesn't give you any accountability in the structure of said product.
Love your friend ❤️ Shane
Namaste, Tyler
I’ve broken 15mm fork axles twice at about the same area as here (where the thread ends). In this area there is little support from the frame itself, and there will be both torsional and vertical stress if the right and left part of the frame/fork is loaded unevenly and/or the axle is undertightened.
I only ride 20mm axle forks and Kalle’s overbuilt german frames now
It's different when your equipment breaks under normal use and you get injured, then incur medical expenses, loss of work, etc. In those cases, it's somewhat reasonable if the design was insufficient or there was an issue that caused it to fail and you end up incurring costs due to no fault of your own.
Showing responsibility is also part of it, for sure, though. For instance, if he was going too fast and slid off the trail and into a tree, that's on him and his poor decision making. If the bike failed, ejected him, and resulted in serious injury due to no fault of his own, then that is something the manufacturer needs to be responsible for. If you have an enduro bike, there is some expectation that it should be able to handle reasonably sized drops, rock gardens, etc without breaking and hurting the rider.
There aren't as many successful frivolous lawsuits as you would think in the US, there is a pretty long running PR campaign to paint some as frivolous to prevent people from suing when it's otherwise justified and legitimate.
On A Team, nobody died, no lower torsos were severed in half by an explosion. That's not real life either.
There are other things to consider, though, depending on how serious it was. If I get put out of work, have to have special equipment, etc.
I also believe insurance companies can sue on your behalf and there isn't a lot you can do about it. So if I hurt myself on the bike because it broke, my insurance provider may sue Specialized on my behalf to recover costs.
You are 100% taking a cultural bias based on TV, not your experience with actual Americans actually filing lawsuits. You tried to amplify it by saying "I've met Canadians who didn't sue".
Now please stop the nonsense and perpetuation of a rumor.
My useless counter argument is I know people with spinal injuries who haven't sued. I even know of people I don't know...who haven't sued. Has Paul Basagotia sued anyone? I don't know. And I don't pretend he has or has not. What a toilet this discussion is.
Go back and read the comment I originally responded to and go back and read the response I was responding to here. Note the countries of origin of the individuals promoting a notion that compensation is in order when there are negative consequences to personal decisions.
Now go and take a look at my geographical location. I'm 20 miles from the US/Canada border. I have plenty of interactions with "actual Americans". I don't watch TV or read sensational politicized news. My opinions on the cultural differences between our two countries are based off of countless interactions with real people, both Canadian and American.
If you'd actually read the comment train with the intent to understand where others are coming from, you'd see that my original point was that suing people after hurting yourself on a mountain bike is generally counter to the entire culture and genesis of mountain biking, and any other "extreme" sport. These sports originated from a notion of "rejecting the system" and generally being rad/gnarly. I can't think of anything less gnarly than suing a manufacturer for a defective piece of equipment that passed through QC.
None of this is to say that a lawsuit would even be successful, as I totally understand that the threshold of proving failure in a duty of care by the manufacturer is challenging to achieve for most situations where this would be an issue. You say below yourself that "everything about mountain biking has been about pushing past what the bike can do". Exactly. I agree. Suing for a bike failure causing injury is thus everything that mountain biking isn't.
Neither is good outcome but it sure is easier to send a bunch of new axles to owners!
Isn’t it ironic that it is mostly carbon frames and components gettijg broken, considering how strong they are supposed to be?
*Next PB news release: Look at this amazing 29.5" 161mm Super-duper-booster-plus-plus wheelset!!!*
The XD driver and similar designs that do not pass fully through the cassette do not restrict axle diameter in the way earlier designs did.
It may not be advantageous - certainly not necessary - just exploring what's possible.
theloamwolf.com//wp-content/uploads/2019/08/Screen-Shot-2019-08-12-at-9.54.11-AM.png
THIS one is however a new one. Never seen a rocky fail like that before. Even on the previous slayer, which also had blind pivots (although it was a carbon rear, haters!).
Personally, a bike breaking in a test like this isn't anywhere close to a dealbreaker for me unless it turns out to be systemic like the Giant Stance from a few years ago (not to pick on Giant in particular, they make great bikes too it's just off the top of my head). After working in shops for this portion of my life, if I could only ride brands that I hadn't heard of a manufacturing defect or two, I'd only be able to ride custom made Moots or something. If it turns out some significant percent of slayers does this, then we'll have a problem. Until then, send it.
Moreover, I don't think it happening shortly in to the test is telling. For people that ride a decent amount or hard enough, most warranty issues present themselves within the first 3 months of solid riding. It sucks because it's a really good way to piss off customers (My BRAND NEW CARBON BIKE BROKE ON THE 2ND RIDE AGGGHHH!!!) but that's the reality. Sure, there's a fair deal that break after but in my experience if it's going to happen it'll happen sooner rather than later for riders that send it. I had my first carbon bike break on the 2nd ride and it was a brand new 2015 model at the time. Likewise my first carbon DH bike broke about 4 weeks in to riding season. Those are examples of my own bikes but when I'm seeing them come back, it's usually pretty quick in to the life of the bike.
Not to mention, PB seems pretty amnesiac... no one here will be riding at this level www.pinkbike.com/news/carson-storch-slayer-raw.html
To rephrase when I say PB seems amnesiac, its not about you or the editors
Excellent point. 50% of all returns of my company's product (in an unrelated industry) happen in the first 3 months. The rest are spread out over the next 5 years. If this is a systemic issue with the design, then it will surely be all over the forums because it will be happening to a lot of new bikes. Most likely scenarios are not a lot of people have bought Slayers yet or its not a common failure.
en.wikipedia.org/wiki/Bathtub_curve
A recall wouldn't be unreasonable here depending on the cause, but speculating is a crap shoot without getting hands on with the frame and possessing detailed knowledge of the design and manufacturing processes involved (hell, even assembly processes given that this in all likelihood originated with the bearing seat). Honestly I think RM is handling this correctly and will give further direction once a root cause is sussed out.
That said it may be fair to conclude PB can't recommend the bike if the tests were incomplete, which seems to be the case.
" it's a shame that one of the most impressive bikes in the Field Test is going to have an asterisk beside its name." Pole review
I don't feel like these two statements are comparable.
We've tried to be as transparent and fair as possible here. If we'd had more time on the Slayer before it failed, as well as a clear answer as to what caused the failure and were satisfied that it wasn't something that would affect consumers, our statement about the Rocky Mountain would likely have been much more similar to the one about the Pole.
First off, we’re really happy to see that Luca is back riding!
When we heard from Pinkbike about what happened, our engineers and technicians began the process of examining all facets of the incident to identify possible causes. We attempted to replicate the failure through numerous test scenarios and during these tests we were unable to crack the chainstay. That said, we’ve taken this opportunity to implement additional quality control measures in our manufacturing process.
The 2020 Slayer is the strongest Slayer we’ve ever built, and it's designed to be ridden hard. It has a reinforced front triangle, reinforced bearing seats, and shielded bearings including dual bearings on the rear triangle.
We’re 100% confident in the Slayer platform and if anyone has further questions, please feel free to reach out to us at info@bikes.com.
As an armchair engineer, I'd suggest over-torquing the axle by 35-40% then loosening it a few times to introduce ham-fisted stretch and fatigue, then finishing with it over-torqued by 40%. Then land a few incomplete tailwhips to the tool-tightened side.
Without even having access to the actual frame that failed, I'll bet this is the exact scenario that caused the failure. If this isn't something you tried in your replication attempts, I'd be concerned that you're going to see more of these on the 2020 frame.
As a fan and customer of your bikes, I want to see you guys fix this rather than shrug your shoulders, restate safety claims, and sell more of the exact same configuration.
You've just stated "After six weeks of looking at our broken product, we have no clue why it happened. So that makes it totally ok, because we're 100% confident in our product even though it did fail resulting in personal injury."
That's quite the brand statement.
It's YOUR JOB to test until the crack is duplicated and you know the reason why your product failed, not until you get bored or give up trying.
You can't say you couldn't duplicate an existing failure and expect to be taken seriously in any way. Imagine if Boeing tried this approach with the 737 max?
This statement makes your engineers and technicians look incompetent. APEGBC will have a field day with it.
And if you are conflicted about protecting your customers then just protect yourself. It would go a lot better for you if you figured out the problem and owned it before an independent lab or the internet does it for you.
I don't know Luca's situation with regards to this being a work place accident. But if it was you can bet WorkSafeBC is going to be looking for a better answer from Rocky than "We couldn't find a reason so we stopped looking"
Until you are certain and can back up what the issue was or most likely was, the least you could have done is tell current Slayer owners to park them until an authourized dealer has taken the rear apart and inspected the most likely areas for failure.
You would have come out ahead taking this simple preventive step as soon as possible. You would at least look concerned about customer safety and look like you were owning it. The added benefit to you is if this turned up more frames with issues it would help you solve or prevent the issue and if it didn't turn up any other frames then it could help defend your idea that it was a one off.
The stub axle on your Toyota broke. It caused a suspension failure and the fender ended up getting bashed. The fender would have been bashed whether it was aluminum, steel, or carbon fiber.
The MTB world is so needlessly tribal with its allegiances. Carbon is great. Until it breaks. Aluminum is great. Until it breaks. Steel is great. Until it breaks.
But when I look at the picture of the axle my first thought is also that it failed due to fatigue. Note also that it failed at the "thread run out" location. The first article I referenced has a good description of the causes of this kind of failure.
The good news is that there are ways of detecting impending failures of this sort. This axle likely had had an issue which could have been detected before failure, saving a lot of pain and suffering.
This is a not too technical article describing bolt failure and it might be a good read for everyone who turns wrenches on their bike:
www.boltscience.com/pages/fatigue-failure-of-bolts.pdf
Dye inspection:
en.wikipedia.org/wiki/Dye_penetrant_inspection
I agree with u jMhills
NYHC FOR LIFE
Off topic, but f*ck yeah!
I've no idea if the axle failed due to fatigue, but after reading that I sure would like to know if it was.
The question is why that bolt fatigued. A bolted joint should normally work by the bolt only taking a load along its length. It povides enough clamp force that the friction between the axle and dropouts cannot be overcome, making that the only load path. The bolt will fail if it's loaded in shear (if the axle and dropout slide, for example). Now I'm not sure there's actually enough load on a rear axle at 9Nm to prevent slippage of that joint vertically (not really sure what vertical load to apply in order to do the calcs). So I would expect that the underside of the dropout cutout should contact the top of the axle, providing the vertical load path. The bolt stops slippage under any other loading directions (which are significantly smaller). Now I reckon a professional rider would notice if the axle were loose (I certainly have when it happened to me), so the only option for fatiguing that bolt is that the load path from axle to dropout is compromised, leading to the bolt taking the load. My suspicion is that the cutout in the dropout is cut too high (relative to the bolt hole), so the axle doesn't contact it, making the bolt take the load. I've never really considered how critical those dropout dimensions are until now. Makes me mildly nervous about running a torque cap fork with a normal axle...
With all that being said, and I do largely agree with your theory, it still seems possible to me that the pivot went first. Maybe not completely even, but maybe just cracked/deformed or even just flexed enough to give the axle/hub/dropout some misalignment which then lead to the axle failure. The whole pivot system could have a number of flaws, improperly pressed bearings, out of spec bearing seat, or even an over torqued pivot axle.
One issue I see with a lot of these modern axle designs is that they do not utilize any sort of pinch bolt to hold the axle in place. Pinch bolts (such as on a fox 40 for example) are great because minimal torque on the axle itself is required, and the the pinch bolts hold it in place without needing to have a huge tension load in the axle itself. On top of that, you really never need to worry about an axle coming loose on you. I know they just got rid of them for simplicity for the consumer and manufacturing, but they do serve a good purpose.
Either way, I know rocky will have the exact cause of this figured out quickly with today’s high tech inspection equipment and other metallurgical inspection, and I’m excited to see what comes of this.
1. The bearings were pressed in crooked and/or the bores were undersized.
2. This lead to a small crack forming at one or both bores
3. This crack slowly propagated until it critical size during use
4. The chain stay failed causing the seat stay to move in an undesirable fashion, which put substantial bending stress on the axle, which caused it to fail at the thread root
Evidence to support my theory: the small vertical lines on the intact side of the bearing bore, which are usually a sign of an over-pressed or crooked bearing
I think it might be time for an MTSB.
Seems more likely that there was a one-off issue with the test bike. Could've been something like Alvey's theory. Could've just been a fluke.
Which is good for Rocky - a singular issue with the test bike is way better than an axle that requires precise torque otherwise it explodes.
And look where the axle is broken, right behind all the threads. That tells me the axle was fully inserted into the threads when it snapped or broke. They said this happened instantly so the axle coming loose just doesn't make sense.
Also I'm sure the guys at pink bike can tell when an axle is loose when they are riding it, The bike does all sorts of weird stuff like shifting poorly, dropping chains, wheel moves around ect.
The axle thread section IS obiously bent and it sheared suddenly, there are only big sharp edges and faces, nothing smooth. Also, why is that axle hollow in that end? For what reason?
There is no way with out looking at the end of the axle with magnification to even really guess what happened. Typically you would expect to see watermarking and then a brittle fracture.
The axle is hollow to give it more resistance to flexing.
And the axle rupture was caused by the frame failure not the other way around, if the axle went first that side of the frame would be load free and the drive side would be overloaded.
Had a crank bolt snap in exactly the same way, at the base of the threads just like that one...
hey @RockyMountainBicycles ...If I am right, you can send me a slayer.
I’m not convinced it was the axle and that pivot design looks sub optimal IMO.
Alternatively, if the bolt had a twisting failure at the base of the threads (like it appears to have) it would have broke, causing the wheel and axle basically to be a lever arm on the chain stay, and the pivot is just the logical point that that would shear/hinge...
I mean ill leave it to the guys at RM to determine what the failure was...but just doing some armchair engineering...from my desk at an engineering firm. not implying that makes me more right, just have spent some time analyzing structural failures and that would be my input
Its not difficult to use a torque wrench to get a rough feel for what difference there is between 2Nm and 8Nm...and when in doubt, make sure things are tight, but be cautious anytime your putting a lot of force into something. slightly less torque is actually better than too much...
I dont know, is it a carbon bars fault for cracking when you over torque your brake levers?
I’d like to see the inside of the chainstay. Depending on what failed first the tire scuffing would likely be the most severe on that side before the velocity was reduced.
Also the more common pivot design where the chainstay clamps the dropout from both sides seems to make far more sense to me.
again...literally EVERY axle, and even furthermore bolt can snap due to over torquing. crank bolts, brakes, disk bolts...any of them can break. make them out of aluminum and that goes up 10x probably, as ham fisted home mechanics rarely bust out their 60 dollar torque wrench to work on a 6000 dollar bike.
long story short, when in doubt NEVER torque bolts. you would be much better off getting a bolt tight, but untorqued than an over torqued bolt past its yield point.
Luca Cometti: 1
Rocky Mountain: 0
robertaxleproject.com
Looking at the failed chainstay pivot closer, I'm leaning towards crack propagation starting there, and more specifically at the stress riser caused by that inside machined ridge that the bearings seat on as it has a sharp transition. You can see the crack starting there and angling outward on the chainstay.
Because the pivot is completely visually obscured by the seatstay pivot once the bike is assembled it would be hard to see the crack starting in the chainstay. The crack may have also started on the inside of bearing seat at the ridge and worked towards the outside of the chainstay, making it harder still to diagnose.
Also if the chainstay had failed catastrophically in one shot, it's hard not to believe that the chainstay pivot bolt there wouldn't have been a weaker link and sheared before or with the chainstay itself.
I wouldn't be surprised to see Rocky address this with a redesigned chainstay without that machined seat in the centre of the pivot and a different bearing and bolt configuration.
I went through the various Rocky service manuals I have to see why this hasn't happened before. The 2020 Slayer appears to be the first model to ever have two bearings separated by a machined rib in the chainstay pivot location. Even the Maiden and the powerplay models only use a single bearing in that location.
On paper, I can see why two bearings would seem stiffer and stronger than one. But on paper, the stress risers from that machined ridge and pressed bearings may not have shown up. Even in a frame fatigue testing rig, if there wasn't a lateral load being cycled it might not appear either. Cycling frames up and down isn't the same as real world cycling of frames side to side.
Step 1: Mount a bazillion strain rosettes in strategic locations
Step 2: Send bike down A-line underneath Forbes, with incentive to land sideways off every jump
Step 3: Process data, develop lab test plan to achieve loading conditions observed in real world test environment (inclusive of all torsional/shear loads you see in these scenarios) plus safety factor of 1.69.
Step 4: Profit!!! (Due to less failed frames?)
Rocky may not have even tested the new double bearing rear pivot with that new bearing seat rib.
They previously stated that the Wade Simmons Pipedream project was the test mule for the this Slayer and they made the Pipedream with the rear end and single bearing chainstay pivots from the 2018 Altitude.
Someone at Rocky may have decided that since they were taking an already proven and tested rear end and just making it beefier by adding a second bearing that it didn't require any testing even though it was a new design.
It might not be the rib that I've pointed out.
It might be something more subtle like the new position of the axle closer to and higher above the pivot than previous models puts the chainstay in more tension at the beginning of the stroke than before or worse, cycles the chainstay between tension and compression, where it didn't before.
Might have been an oversight, might have been cost related, might have been in a rush to market. Only Rocky can say.
If a lawyer for Luca, Pinkbike, or worse, another injured rider comes calling, I hope Rocky has all of its development and testing well documented.
The frame failed over six weeks ago. That's a lot of time for Rocky to figure out what happened, yet based on their statement for this article they don't seem to know yet which I find more troubling than the failure itself.
Or they may already be in PR damage and liability control mode.
The giveaway will be any design changes they make in that pivot going forward.
Once there was a crack within the bolt from it being overloaded (torque wise) then all it would have taken would have been a slightly botched sideways landing to put some lateral forces into it and it would have split. once the bolt snapped there would be no tension to hold the rear end together and the wheel and axle would have just been a lever arm on the entire non drive side chain stay, and the likely place it would break is where there is the least metal (the thin spot at the bearing housing. as far as I have understood (with my measly technician brain) Aluminum is not a terribly good material when it comes to tension... Personally I think this might be another example of why aluminum is a terrible material in anything with high torque requirements.
Not arguing with your points or anything, super informative and interesting! just curious on what makes you eliminate that as a plausible option
I can also be wrong. It may have been an over-torqued axle but I think it is much more likely that it is a design or manufacturing flaw in the new chainstay. Only Rocky can say for sure. And I've already pointed out that if they don't actually say anything after looking at if for over six weeks, any design changes will speak for them.
At first, I didn't have an opinion either way, whether it was the axle or the frame. Like everyone here I was looking at the pictures and trying to figure it out. That's when I described the method for checking the faces of the failed parts for smooth and sharp faces as it might have suggested or ruled out which it was and wishing the pictures were higher resolution.
I would agree that the axle most likely failed in tension. The problem is I couldn't tell from the photo but as many have pointed out, the way a thru-axle sits in a frame it makes shear failure very unlikely. Then the question is, even if we all agree the axle failed in tension, did that tension come from over torquing or from the frame spreading as the chainstay failed first?
In my second post I started to lean towards the frame going first from the shape of the failure and that is when I noticed that the crack the chainstay failed along runs up to the that new bearing rib. I also didn't see the chainstay failure as catastrophic, as from the side photo the metal looks bent and worked as opposed to shattered into a few bits. I think this supports a crack that worked itself bigger over some cycles.
I also thought that if the axle was cracking first, say from an over-torque, there would be signs. As the crack was working through the axle from the threads weakening it, the riders would feel rear wheel play as if the axle or hub was just loose and none reported that feeling in the bike before it let go. Another point is that the mechanics were pulling the axle in and out often to change the tires. If the threads were starting to go, the threads would start to deform and the mechanic might either see this or feel it as the axle would be harder to start to engage at the threads when they replaced the axle each time. Last, if the threads had started to crack and fail, the mechanic wouldn't be able to get the required torque on the axle with a torque wrench anymore without the axle breaking then. I feel all of this supports a sudden axle failure over it failing from a crack from cycling.
So this brought me back to thinking the frame went first. Then the next question is why? Rocky has made thousands of bikes with chainstay pivots and thousands of other bikes have been down A-Line. What was different? Was this double bearing and rib design new or the same as in other Rockys? I didn't know so that's when I flipped through the service manuals to see if this was a new design or already used in other Rocky models. It appears to be a new design.
When trying to determine cause of failure, a new element, like the chainstay, is usually more likely than an older proven element, like a thru-axle.
In terms of quality control being a factor, it is much easier to maintain and test strength on something simple like an axle compared to a chainstay. It is common practice and inexpensive to test a handful of bolts to failure from each batch to make sure they meet spec compared to testing a handful of chainstays from each batch in the same way. Likewise, I imagine axle manufacturers have tested failure from over-torquing in the process of specifying the proper torque to use. It would pretty easy to build a jig with a wheel in it, over torque an thru-axle to different levels and drop weights on the edge of the wheel to see how much over torque it takes to compromise the thru axle when the wheel is side loaded. Even the staff at pinkbike could manage this one for an article so I suspect manufacturers already have.
If it was the chainstay that went first, it might be the new design of the bearing seat with the rib causing unanticipated stresses or it might be the quality control of manufacturing this new design. The design may be fine but it could be a bad batch of chainstays that were being made differently for the first time.
And to be fair, it could be something else entirely. Like I said I'm not necessarily right at all.
I've just tried to put my best idea forward based on the info and experience I have. If I was Rocky I'd be working very hard to try and duplicate the failure and see what I could rule out and what I needed to focus on.
for sure can follow your path of thought on that. The fact that the rear end appeared to have a "slower" failure is an interesting point, and I am going to discuss that with the engineers in my office. a few of us have taken some interest in this as a bit of a fun distraction from our normal work. I think the fact that they had a mechanic on hand is one of the more interesting points on this for sure, as personally I would have thought either problem would have surfaced in a mechanical check prior to riding. you would think that a crack in the rear would have developed a bit slow and would have also developed a bit of play or roughness before complete failure. but I also agree you would think that a bolt failure would be noticeable too. That is why I find myself keep coming back to the bolt, as it is the most likely human error problem. is there any chance at all he accidentally over torqued the axle? or even furthermore...was this just bad luck and a manufacturing fault existed in this bolt and did it just twist even under normal torque values?
In my head this wasn't even a problem with the threads, but a bolt that was both over torqued AND also threaded in completely to the base fo the threads, thus putting all the force on the section of the axle that tapers from 12mm thick to whatever thickness it is at the threads. Another guy *(Dangerous Dan) above posted an interesting article on how running the end of the threads into a bolt (or in this case the frame) and how that causes fatigue cracking within the bolt, until the axial torsion just twists the bolt apart. the sharp edges of that bolt in the images look like a spiral failure, as it almost looks like a ramp from the side ( not a clear shear failure)
Otherwise I fully agree with your assessment. they re using a lot of technology that already exists in their other bikes, so a logical first step would eb to analyse anything that is different. but with that said, I guess changing one part in the system could cause failure, even in already existing parts. really at the end of the day it is only RM that will know the true answer, hopefully its just bad luck...I wanted a slayer. but this is a nice reminder that the first iteration of any bike, can come with its flaws.
Interesting none the less and appreciate the response. look forward to getting the "truth"
My 2 cents…
- It broke catastrophically...
Two on the mountain and the RM aint jumpin
cause my axle aint whole
I got stitches in my arms all swollen and bruised
I will say, I own a 2017 Element and treat the thing like an Enduro bike and have even done some DH "racing" on it. It's got over 1500 hard miles, mostly XC racing, and as much as I've felt under traveled on stuff I've never lacked confidence in the frame.
I also appreciate that Rock Mountain simply took the feedback in stride and didn't try to blow smoke up anyone's a**. I think that admitting that upon first inspection they were unable to provide an explanation but suggest that they will do some sort of failure analysis to get to the bottom of it shows that they are concerned about their product and customers and want to get to the bottom of this so that they can continue to sell products they want to make that are also fun and *safe* to ride.
But the number of comments in here that state that this one SINGULAR failure on one SINGLE model means that people suddenly think that Rock Mountain is a horrible company that no longer knows how to make a bike is just ridiculous. It's perfectly reasonable to watch for Rock Mountain's final response for this and seek out what conclusions they draw and what corrective actions they employ. You should look for this information! I will be!! And hopefully the answers to those questions bolster your trust in the company.
(can't believe that pun was still available)
Anyway, here's to an update in the future hopefully once the issue has been properly diagnosed.
Will be interesting to see what RM find out.
In my case the axle had 2 years of use and had come loose on a few occasions (my fault for not checking). The loosening is likely a contributing factor to the failure possibly combine with over tensioning of the axle.
Even with the axle broken if there was a milled channel for the rear hub to sit in the rear hub couldn't really have come out of place bad enough to through a bunch of torque into the lower pivot causing it to explode.
At $7k, there aren't any component compromises on this build, yet the bike is still heavy-even for a 29er enduro bike. With such a light build kit (XTR bits, carbon cranks, etc.) that means that this frame/rear shock weights around 8 or 9 pounds. That's enough material to build a bulletproof aluminum frame....period.
Rocky Mountain as a brand big enough that their engineering and design has to be spread across a complete bike lineup, but small enough they don't have a large R&D staff. Big enough that their frames are likely made by one of the high-volume manufacturers in Asia, but small enough they can't afford the kind of dedicated fittings like dropouts and pivot assemblies/hardware.
Pinkbikers don't like to hear it, but unless you're willing to spring for the Gucci tax of a reputable boutique brand, your best bet is to get a bike from the big 3. Bigger engineering departments, better QC in Asia, and proprietary parts where warranted are standard for them. Those frames break too, but much less often and usually with better warranty coverage.
Lol.
Name a brand that touches the big guys on warranty rates.
Just because they have good warranty doesn't mean they break less often.
Carbon reign 2015-2019 frames broke like nobody's business. Anybody that rode one even remotely hard broke one.
Trek chainstays - again ride the bike properly and it WILL break. Yeah they have good warranty, but I'd just rather my stuff didn't break.
I haven't worked at a shop that sells a lot of rockys but I certainly haven't heard about them having many issues.
Mostly 2017+ remedies with crappy ABP bearing seats. The bearings creep out
While I do think the ‘20 climbs great for it’s DH capability I’ve decided to keep my ‘17 Slayer as well for the more pedally trails. I find they compliment each other well. I have since passed along my DH bike to a young shredder down the street from me as I’d never ride it again. PB saying the 20’ lacks high speed stability. Hmmm. Maybe it’s relative and the other bikes are just that awesome as I wouldn’t say the same from my time on it so far. Perhaps I’m not pushing it to the limits they are. ????????♂️
Good new though, the bike was fine.
Also broke the rear chainstay on the same bike in one season riding.
Oh wait! To me...TWICE!!
My Element AND my Altitude...
Loved the Ride
Lots of things cause failures. Funny how almost 100% of mountain bike production has gone to china but bikes keep getting more expensive...
Are you saying Kona is Canadian? Cause it isn't, just about 40 miles south of the border
Cool I'll go drive over to their shop and tell them they are actually in Canada.
how you can over tight this type of axel?
on the other side all bike brands have frame failure, some of them have shitty excuse some of them nice warranty
Option two would be: the axle threads were improperly machined (too deep or too long), thereby causing the threaded area to be the only supporting element for the forces coming from the wheel --> axle failure leading to pivot problem mentioned above.
My conclusion is that the threading on the axle was either a) too long, or b) cut too deep. Again, based on my limited knowledge this is just a theory, but when threads on a bolt fail it's typically because the bolt was loaded in a way which bolts don't deal with well, which is a powerful radial load.
This is an issue which caused a rider to crash and get injured and therefore a catastrophic QC fail. Could have been life threatening. It happens in every field, but there's a reason that FMEA and other QC systems exist.
On the other hand, this could have just been bad luck.
And THIS is why Rocky Mountain needs to keep the Maiden in the line up! Long live the Maiden!
Sorry for Luca, sorry for Rocky Mountain. Certainly a surprise. Any bike can fail, but didn't expect it to be from this brand and especially this model. I've had many a Rocky Mountain, and never had anything major like this happen. It doesn't make me any less apt to get one, I'm currently hankering for a Instinct to compliment my Wreckoning.
I still ride my old-school 2008 Slayer SXC and it didn`t break yet. Still a smooth clockwork... but it was aluminium era!
You`ll fix it out, for sure ;-)
... and if Pink Bike would have tested the aluminium version, what would have happened??
Also Pink Bike: watch out your language; so-called experts in pampers like you shouldn`t talk like that.
Kaz finally grew out of pampers last year.
I have seen a few Rocky axles in their FS bikes become overly tight and in extraction this is exactly how the axle brakes.
I believe Rocky also produced a video on how to effectively remove an over tightened axle.
Perhaps that impact was enough of a forceful test on the axle after the threads had locked to spiral snap it?
I am curious to hear the actual outcome of Rocky's investigation.
That aluminum axle, especially if it had a lot of tire changes, had been tightened and loosened too many times. Very likely had been tightened by hand much higher than it's torque spec. (with the assumption that it had a properly calculated torque spec ) It met it's fatigue life, and began stretching at those last few threads. Once that began, the axle was doomed.
It's possible the ALum axle was under spec'd, or bad heat-treatment, but more likely it had been over tightened way too many times. I would guess a close up of the fracture surface will look like a textbook example of this particular failure mode of threaded fasteners...
This isn't Rocky's fault. (although one could argue they need more margin in their safety factors, perhaps,) But the fault of one of the people who ever touched that axle...
I have seen the exact same type of failure on bolts just like this in my professional life, I'd wager a fine bottle of scotch this failed because the axle was over-tightened too many times.
Time for a recall.
When out of valid arguments go with the latest saying huh.
AXEL: Dude’s name in German and a few other languages.
Güd spelling is for loosers
Aluminium yield strength / machine cut thread X torque X force (huck on A-line) = that axel
Cascading Effects... busted up chain stay
Soon to follow- torque specs printed on all axles.
" Bike experienced a RUD event when....."
RUD = Rapid Unplanned Disassembly
Will be curious to hear what the follow up will be?
Crash replacement?
If the axle were the cause wouldn't the break have been on the drive side as it was the only side still connected?
I did break an aftermarket axle like that once when I hit a stump. I had over tightened it as it kept coming loose (before I discovered lock-tite).
Is there going to be an overall round up on your favorite bikes regardless of category?
Oh and can somebody remind me to get good enough at biking to just *warm-up* on dirt merchant ha ha.
I don't usually comment on posts, just read them.
But I think it ist better do show some compassion for the people who buy bikes for 4-5-6-7-8 K, and thann something like this happend.
It was the same when the yt launched the Capra cf, 2014 the frame was broken on the isgs chain holder.
One thing is a fact, the big companies, no mather what do they built, they do not test anymore that good their products,
Couple of hours on a normal bikepark, no big gaps, no pro riders, and than on the market.
It's all about fackin money ????, money and again money ????.
It's pretty sick to watch your bike completely destroyed from a hospital ????....
So that's all folks.
If you reverse the series of failures it makes much more sense. Something about that pivot failed and as it started separating it sheered the axle in the process. Hard to guess if it were a loose/out of tolerance bolt/chainstay, or simply not enough meat around the bearing. If I had to put money on it, I'd say something was out of spec with that pivot bolt assembly which lead to a fatigue failure somewhere further up A-line and and ultimately a catastrophic failure right about where poor Luca hit the ground.
Heal up Luca!
One way or another something is fishy here, and RM's response is totally wrong IMHO. If a failure of this nature occurs and you have no idea how or why it happened, unless you're damn sure it was user/installer error, you don't get to claim the thing is perfectly safe to ride and it's no big deal. The fact that they brought it back for testing to see if it was an early model that missed heat treat is a huge red flag as well. How is that even a possibility?
I disagree with RM's assertion that the bike is totally safe. Clearly it broke, so either their testing is inadequate or their quality control is. You can't claim the bike is safe if this example was within tolerance and failed the way it did, and you can't claim the rest are safe if this one was out of tolerance but somehow got through QC. If they suspect failure of the axle due to improper installation, that's an easy one to test, and being a brand new bike with a brand new axle that wouldn't have been removed and re-torqued more than a few times fatigue shouldn't have been a problem unless Pink Bike's mechanic was really ham-fisting the thing.
The pulled apart pivot is a consequence to the axle breaking and the wheel twisting. It started with the axle failure and progressed from there. Wiithout the axle snapping upon landing the jump, there isn't the energy to twist the wheel enough to yield failure the pivot.
First of all bikes are not indestructible .......
Then.......what about considering the option of a really bad landing ?
İ mean its a enduro bike
nah, it's frame sucks!
because if it is not destroyed there is to be complimented the RacaFace!
but then RM spec'd a house brand axle?
m.pinkbike.com/photo/18088859
There are rumors of a loose axle being the fault.
Bike Manufacturers: Lets send them some bike made of tofu.
2) Always use a torque wrench on your bike and ALWAYS use lock-tite on your axles. EVERY SINGLE TIME. They simply don't stay on tight at the torque values allowed.
3) I've always dug RM bikes and they are a brand I'd have had on my radar. IMO RM needs to send new chainstays and beefier rear axles to every current owner of these bikes. The chain stay should absolutely have lugs to hold the hubs in physical place (as should all bikes) so that the axle locates the rear wheel but the aluminum chainstays, not the axle, is where the force from rear suspension compression goes.
4) Saying there is no issue doesn't give me the warm fuzzies and this isn't a bicycle I would ride at this time. I already got ERed when a motorcycle part failed and don't need any more of that in my life.
5) Even though Pole's response was BS, at least riders can rest assured they are changing the design which failed.
Good luck Rocky Mountain, this is going to hurt.
Regarding (3): As far as I know all RMB designs, as practically all bikes, have the rear wheel slotting vertically into the dropouts. Once the axle is loose - or broken - any landing that's even minutely off-center will cause the rear wheel to rotate out of the frame anyway. In this case the axle was broken on the right side, so the rear wheel twists out of the dropouts in a clockwise fashion (assuming you're standing behind the bike).
Tried overtightening bolts to get thru a single ride without them coming loose, and the parts then just broke, frankly in a manner not dissimilar to the photos of the RM axle.
I was told to lock-tite them and since, no more problems. They make a thread-locker that just puts a bit of dry rubber on the threads so it doesn't back off, and that's what I use now.
Your experience may vary, but I'm sticking with it.
@SunsPSD: yes definitely locktite rotor bolts, and caliper bolts.
Also. The closeup of the chainstay reminds me of this
upload.wikimedia.org/wikipedia/en/thumb/e/e5/Graboid.jpg/220px-Graboid.jpg