Video: Neko Mulally Shares the Details on the Development of a Carbon Rear Triangle

 Agreed. Neko's whole series on his bike has been super amazing.

 carbon can "fix" shit designs. see devinci's older wilson. was all alloy, rear end kept cracking, went to carbon. also look at evil, alloy bikes kept blowing up. went to carbon, evil bikes blowing up less?

 @taskmgr: lol

 @taskmgr: yeah but evil is edgy with tattoos and black tshirts.

 @cogsci: lol true

 Trek spend a tonne of money on racing and their newest Session is full alu. They're the biggest bike brand out there and they clearly don't think it's the be all and end all

 @tom666: Commencal don’t make carbon bikes because they don’t like the impact the process has on the environment etc. (Decision made in 2012 per their webpage). Maybe Trek are taking a similar approach.
Each material has its strengths and weaknesses from a design and manufacturing point of view.

 @Bhaack: The reason why Trek use Alu because their riders feel really good on Alu prototypes to the point they think they dont need a carbon version of it. Thinking about it even Loic Bruni didnt even ask for a carbon version of his bike. It is all about their approach some bike feel good on Carbon and some feel good in Aluminum.

You can watch why Trek choose Alu on their youtube

 @ErlJerwinMartinez2ET:
Wouldn’t be surprised.
I keep hearing of DH racers going back to aluminum rims from carbon.

 @ErlJerwinMartinez2ET: Thanks. Hadn’t followed that closely. With these guys being really fussy about wheel stiffness as also noted, and you hear from the pits they often want specific spoke tensions (potentially meaning the wheel doesn’t last too long), it doesn’t surprise me that feel is a big part.

 @ErlJerwinMartinez2ET: now it's the other way around... Prototypes are carbon +3D printed titanium...

 LOL!

 On a DH bike, where pedaling efficiency is not as important, I agree

 @ak-77: Here's an article comparing a Nicolai bike with a gearbox vs. same model with a derailleur and there was a real difference in the suspension www.pinkbike.com/news/nicolai-shootout-derailleur-vs-gearbox-2017.html

The center of mass of a swing arm is not that far from BB so no wonder it made a smaller difference

 I'm with this... NEKO should be testing gearbox vs traditional design. This is a no brainer - comparing notes with Paul Aston maybe as well...

 @kanioni: Nice thing is, you can do both. And when the wheel is lighter, the swingarm makes a bigger difference. I checked the link you sent, Paul should team up with guys like Dan Roberts or Seb Stott, who understand a bit more about the physics, so they canmore clearly link his riding sensations to their cause. That drop test is not a way to test the effect of unsprung weight if you ask me. I mostly tells you that your rebound setting isn't way too light. The test to do is the opposite: how fast can you lift the bike up from a compressed state without the wheel leaving the ground? But that is very hard to do reproducibly without equipment.

 adding gearbox might also move some of his pivot points if its on the way of the box also but yeah its the best way to achieve it

 @ak-77: I cant feel any difference in efficiency between my pinion zerode and my 12 speed xt stumpy.

 @ak-77: yeah I also think that a drop test is BS in this context. And I agree that a light swing arm is a nice bonus, but still kinda a let down at least in Neko's test

 @plustiresaintdead: nah. Incorrect. If they skip prototyping its because they stole geo off of another bike and their industrial designer is the only "engineer" in sight.

Might be something else entirely but it isn't likely because they don't have the money.

 @oronaut: it’s always about money. In the scenario you offered it’s because they don’t have the money to hire an engineer.

I’m not saying this is some horrible thing. It’s just the way it is.

 @plustiresaintdead: 5-15k! Wow time to treat myself to a bigger shed and that tig welder I’ve always wanted.

 Did he mention the cost somewhere? 40k sounds steep!

 He said it was 20 times the cost of prototyping the other. Just an estimate but based on my experience purchasing similar molds for other types of manufacturing $40k was also my estimate.

 He has that team owner vibe going

 @nolimit:He said tooling for aluminum was a couple thousand dollars compared to the tooling for carbon which is about 20 times that. So, it is just a guesstimate on my part from what he said. @14:28.

It does make sense if you are selling a good amount of frames though. I can see why a lot of guys that got a lot of experience working in the industry are branching out with their own companies. Free market competition is good.

 @tacklingdummy: Yeah, tooling for carbon frames typically costs 30-50K depending on complexity, that's why manufaturers prototypes in alu and go to layup when all geometry design is in place.

 Leg dyno*, if you’re seated going downhill you’re doing it wrong.

 @Murphius: I'll just leave this here... This guy won a few races or something, I think.
m.pinkbike.com/photo/12763562

 What concerns me is that he didn't realize how much stiffer his initial Alu rear triangle was than other comparable designs, and when he went to a more flexy carbon version, he also didn't notice a difference... so either the rear triangle stiffness isn't that big a deal, or he isn't actually that sensitive to the difference?

 And, how close to the axle has that weight been saved?

 @Untgrad: methinks swingarm weight (or lack thereof) is nearly insignificant relative to the weight of the wheel that's bolted to said axle when it comes to unsprung weight. no surprise that a rider (even of niko's caliber) couldn't discern a meaningful difference.

 @xy9ine:
..exactly!

 @Untgrad: I was talking with one of the smartest suspension brains in the bike industry about wheel and tire weight. I think the topic was downhill tires and tire inserts on enduro bikes. He told me he really doesn't think the extra weight makes a difference in practice and the benefits of the extra weight (tire stability and flat prevention) wildly outweigh any perceived difference in unsprung mass. I'm not sure if he's right, but he is a lot smarter than me. After that conversation, I wasn't surprised to hear Neko say the same thing after testing the carbon rear triangle. And shaving over 800 grams is not a small amount. That's like going from a downhill tire with an insert and a 400 gram cassette down to a 200 gram road cassette and EXO tire.

 @TEAM-ROBOT:
Thank you for that!
That’s exactly where I was going next. I love 29 inch wheels, and for me, the heavier the rim, the better!
At least for going downhill.
I wonder if the gyroscopic effect of the spinning wheel negates most any weight loss at the rear triangle.

 @Untgrad: Gyroscopic effect has little to nothing to do with suspension performance. There is one aspect that is important for rear triangles but not for forks: you have to count each bit of the unsprung mass by how much it moves during suspension movement. Imagine you divide the whole rear unsprung mass into a million parts. The effective unsprung mass is then the sum of all the masses of these parts times how far they move relative to the wheel axle movement.
The benefit of low unsprung mass is this: when your wheel goes over a bump it moves up. When it is at the top of the bump it is still moving up, but the floor is now moving down. To regain traction, the wheel has to move down. It will accellerate down with an accelleration that is (spring force-rebound damping force)/(effective unsprung mass). So lower mass directly translates into better traction. This would be most noticable over fast chatter that's a bit more than tire compression alone can handle.

The case described here, with an 800g weight saving of which about half is effective mass, with (guessing) 3kg of wheel/tire/cassette/chain/rockerlink etc, is about 10% increase in wheel reaction speed.

In specific situations, like a flat corner with a lot of small fixed rocks, or straightline braking over (non-slippery) roots, I would have thought that would be noticable to a pro like Neko. But apparently it's not.

 @ak-77: Great explanation, and to be fair Neko also thought the difference would be more noticeable. It's pretty cool that he's doing this sort of back to back testing on common suspension theories and sharing his findings. Super interesting.

 @TEAM-ROBOT: Thanks. I wonder if he also tests with telemetry on the bike? To a nerd like me it would be interesting to know if the lack of noticable difference is because the difference in movement of the wheel is much less in the real world than the naive guess, or that it takes a much bigger difference than 10% in practice for a rider to notice.

 This was done the wrong way around. It would have been simple to add weight to the existing rear triangle and check to see what difference that made.

 @dave-f:
Sounds like a job for M-Levy..
Damping is configured to the unsprung weight of any well designed suspension system, among other factors like friction.
But less unsprung weight is always desirable.
F1 cars used to have their suspension components replaced after every race. Everything is so marginal for low unsprung mass that it wouldn’t survive two races. Or even one!

 @ak-77: then the type of track and the conditions - softer or hard and chattery would impact what you feel. Wonder what track Neko tested it on.

 @Untgrad: I am no suspension tech person, just a mountain biking physicist shooting from the hip, but I would think that in most mountain biking the damping is not tuned to the unsprung weight. One way of tuning rebound is that you tune it to be as fast as possible without pogo-sticking you into Friday Fails on bigger hits. The unsprung weight then affects how much that setting compromises your traction.
All in all, there is a lot of variables that go into the shock tune, and they all affect each other. Low unsprung weight will help you make more advantageous compromises.

 @ak-77:
Right! And LOL to the Friday Fails comment!
I know Porsche used aluminum lug nuts on the 911 back in the day. And magnesium rims were a big deal on sports cars, probably still a thing. Unless you go full carbon.
The ratio of sprung vs unsprung is a thing. The higher that ratio the better. I assume one reason modern Mtn bike suspension works as well as it does due to the bike, plus rider, vs the delicate little “wobbly bits” called chainstays and forks.
But I’m just shooting from the hip..
P.S. Wobbly bits. For the British readers eagerly awaiting the start of the F1 season.

 @Untgrad: Yes, the ratio matters because the sprung weight sets the spring force, which is the driving force to get the wheel back on the ground. The ratio of sprung to unsprung weight hasn't gotten much better for mountain bikes, 29er wheels aren't lighter and though obesity keeps rising the top athletes aren't heavier than 10 years ago. It's the dampers and springs and seals that improved.
In any case lighter riders may notice improvements in unsprung weight quicker than heavy ones.
For cars on pavement, suspension is much more about keeping traction and less about absorbing impacts than it is for mountain bikes, so they make different compromises. I think rally cars and MX are better to compare to than 911 and F1.

 @Bhaack: Yes indeed. I've been thinking about what would be a good test track. One would be rear-only braking over dry roots. That minimizes rider input variability and should give an idea of how much less the wheel skips over the trailing edge of a root. Of course this requires suspension that is very active under braking.
A more relevant situation would be a flat corner in hardpack embedded with fist-sized rocks. It's a bit more dependent on cornering technique but a pro rider tuned to his sensations should get the idea pretty quickly.

 @ak-77: i have some tracks with some corners - some with berms - with substantial breaking bumps from slower riders. Whereas faster riders don’t even break. Just getting your speed the same between runs would work. And stay off the brakes.
But maybe you don’t have those track situations.

 @Bhaack:Braking bumps are good testing ground too, and they're everywhere. Unfortunately, I don't have a mold for a carbon rear triangle of my bike to test it :-) Besides, on my not-very-overbuilt 120mm xc bike the weight difference from going to carbon would be very small compared to 10-51 cassette...

 It's more than just weight. The more advanced builders (companies) do a lot of things with variation in thickness of the carbon in different sections of the frame. That gives specific flex and stiffness properties in those locations which then allows the frame to perform (ride) a certain way. You can't do that with a standard metal frame. I'm not saying one is better, I'm just describing the process.

 @mybaben: They have been using different wall thickness in bike frames for years. Along with different shapes to accomplish the same goals. This is nothing special and if you think that they can only do this with carbon frames the marketing team is doing their job well.

 @johniep: That's true they have. And I did not say they can only do this with carbon. It's just easier. have a good day eh.

 @mybaben:
I thought a version of that is going on with tubing shape and hydroforming.
I guess that’s an assumption.

 @johniep:
..ouch

 @johniep: You don't quite have the whole story; with carbon you can not only change the shape/thickness easily, but you can also change the weave type and orientation in the layup to tune the ride characteristics. The individual weave layers can be 45 degree, 90 degree, 60 degree, unidirectional, etc. Each layer can be different and there can be 20+ layers.

And then there are different grades of carbon as well as types of epoxies.

Carpet Fiber is infinity more "tuneable" than any formed and shaped metal on the planet.

 @bikebasher: I get what you're saying, but look at a modern high end aluminum road bike like a CAAD13 or Trek Emonda AL and you're going see an incredible variety of tricks and tools and tubeshapes used to generate varying amounts of flex and stiffness in different directions. Wall thickness, butting, tube shapes, monocoques, hydroforming, etc. I agree with you in theory that carbon is the most tunable material, but that doesn't mean it's tuned as much or more than aluminum in actual practice in the bike industry. For instance, most carbon frames use the same layup pattern for an XS frame intended for a 120 pound rider as they do for an XXL frame intended for a 220 pound rider. The point is, I think aluminum and carbon are both wonderful materials for a bike frame that can accomplish pretty much any ride quality a bike manufacturer could want. The only real difference for the end user of the average aluminum frame and the average carbon frame is weight. This isn't aerospace where the best and brightest minds are spending hundreds of millions of dollars to optimize carbon wings.

 @Untgrad: Yes, that's true. You can achieve similar results with all those techniques. I was responding to your comment about carbon and its weight and mentioned the variable thickness aspect too and the benefits.

 @mybaben:
I actually posted that seconds before your post..
A little late on the draw for me.

 @Untgrad: Cheers.

 @mybaben: with such massive weight and fearlessness discrepencies between customers surely they’re overthinking stuff or these frames are truly amazing for mr. Averageweight? Most bikes have exactly the same stays from small to xl…i think?

 @Kebabroll:
That was just beautiful..

 To be painfully obvious, he’s developing a downhill bike, not a trail bike. For this program there was no perceptible benefit and I don’t think he said otherwise.

 @Yody I'm curious why you think unsprung mass would be more noticeable on a trail bike with a short stroke shock?

 They have high sprung masses too, so the sping forces are higher. The reaction speed of the wheel (simplified) goes as the ratio between sprung and unsprung mass.

 @ak-77:
MX bikes need to be throttle on though whoops. If you go trailing throttle in the middle of a whoop section, you’ll find yourself on the ground.
My old CR250 Honda had horrible rear suspension that had one trick- accelerating through whoops and other chop. It was a big compromise. MX racers didn’t mind.
While lighter unsprung weight is always good, MX bikes focus more on the rest of the package.

 @Untgrad: I had to Google what exactly whoops are, I know next to nothing about MX racing. But seeing it now, I understand. Unsprung mass is important for the situations where you want the wheel to follow the ground as much as possible. That is not quite applicable to whoops. The only advantage I see is that with lower unsprung massbyou might be able to run a lighter compression damping but that depends on other factors too.

 @ak-77:
The MX bikes are all about fore/aft weight transfer. Traction under acceleration, the right amount of front end dive under braking, and a cockpit that lets you slide your mass from over the bars to the rear fender.
A lot of the same concepts as Mtn bikes, except a 450 four stroke seems designed to dislocate your shoulders when you twist the throttle!

 To Bushmaster- Exactly!