Dylan & Peak Torque explore cycling suspension & cognitive dissonance

When I watched Peak Torque’s video this morning, I was really confused: why is he even making this video? The point is so obvious. Then I realized it was a response video and it might not be obvious to some. But yeah, if you pedal long and hard enough you can literally feel your dampers heat up. That energy has gotta come from somewhere.

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Back in the day :tm: full suspension designs were quite poor and suffered from severe pedal-induced feedback. The force in the drivetrain would compress the suspension. Since none of us pedal in perfect circles I believe that this oscillatory motion would actually result in a measurable loss of efficiency between the pedals and the dirt.
I’m not sure that this is what was trying to be shown in the video but the results indicate just how far we have come in therms of FS designs.


I think you missed the point…power to the cranks is not the value to be measured. It is whether power is lost through drivetrain inefficiency as a result of the FS design. So the power at the cranks may be the same (the input, if you will) but whether that same level of power is being applied to turning the wheels (the output) is the same.

Look at it another way…the power to the cranks could be the same on two road bikes….but one is running 20 psi tires and another is running proper psi. Will the results up a climb be the same? Of course not…one bike is less efficient.

I know I’ve had a lot of fun with power meter pedals and a powertap hub…even though a lot of the stuff we looked at got swallowed up by the accuracy of the meters. A similar approach would be interesting on a suspension bike, though. I bet we’d get a measurable result in this case.

I’m not sure any of this can really be generalised. Controlled efforts on roads or smooth trails aren’t really going to represent how fast you’ll get up a technical climb in race conditions. It doesn’t look at how open/closed or full sus/hardtail will respond to the big accelerations. There’s also going to be inherent bias from each of the guys making the video.

I’d wager that someone could perform the same experiment can come back with results showing that there is a difference between locked out and open.

Even the studies that Dylan quoted were so small that you’d need to question if the results are generalisable.

Interesting and fun, but a bit of Bro-Science if you ask me!


Revisiting this, that the damper absorbs some pedaling energy is actually completely irrelevant for this test, which is why the results are what they are.

@russell.r.sage nailed it the first go around.

Strange that Peak Torque didn’t include HR data for seated locked/unlocked though. I think it’s zero surprise to any cyclist that standing (on any bike) has a higher energy cost. I suspect that HR would be only slightly elevated between locked and unlocked while seated, and perhaps a longer run would be needed (still we know the limitations with HR in general).

It’s so tempting to discuss the energy exchange dynamics with our pedaling and suspension but as PT says, it’s pretty irrelevant for this test. Which points to the severe limitation of this test in the first place.

So for another test like this one we need more HR data for locked/unlocked. Standing data is irrelevant IMO. And a higher power output standard. I’m guessing the results will stay the same though.

I’d like to know which method produces the fastest time up and back down a 1 minute technical climb with a full gas effort?


To your point, the first thought I had was, “how often am I mashing up a paved climb on a mountain bike race” but i understand why they went this way. You’ve asked a much more complex quest and considering we don’t even have a good answer for the first (less complicated) question I doubt we’ll be able to quantify that any time soon.

That’s part of what make MTB soooo much more interesting to me. Rider A mashed up the one minute climb with the shock in a middle compression setting, Rider B spins up with the shock fully open. They arrive at the same time with different techniques. Which is better?


Apples and oranges, I think….clearly suspension benefits a rider on technical terrain. What they were trying to isolate was whether there was any drivetrain losses due to having a fully active suspension system vs. locked out on smoother areas (where you would actually, in theory, lock out the suspension)

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Simply agree. Problem is thst less and less availaible, if any, hub based power meter exists. There is an easier way, though. What about fulls suspension MTB on trainer, in erg mode, designed experiment, same rider, alternating days open vs. closed dampers, without any sort of power match from the pedals? Could build this with multiple riders as well. Measure the delta between power meter pedals for average power compared to power recorded by trainer, and COMPARE the values between open and closed. Could get volunteers from this forum even, and share the data, analyze, arguably crowd fund a peer reviewable paper. The workout doesnt even have to be hard, could be Petit, which would allow data from once a week for 10 or 20 rides, normalize to percentage, and crunch the numbers.
This would give analytical differences, if any. I though the purpose of suspension was to make riding more efficient? Once I adopted (albeit late), full suspension, I was able to ride up so much more trail than on a hard tail. Descending was more comfortable, but I haven’t ridden down anything that I wouldn’t have on a hard tail. Experimental desing would be easiest, by isolating everything you can. This can be analytically studied with a trainer. HR can also be recorded.

This reminds me of this classic GCN video with Sy and Matt:

They test a road bike, cross bike, and a XC mountain bike over the cobbles of Roubaix. Surprisingly, the least aerodynamic bike was the fastest and required the least amount of power to the pedals.


I’m now taking this as definitive proof that mountain bikes are clearly the best bikes for all occasions :stuck_out_tongue_winking_eye:.


The real issue at hand is whether it is harder or easier to climb at a given speed with the suspension locked or unlocked.

The law of thermodynamics and basic human intuition says “duh, of course it’s less efficient to shunt your watts into waste heat.” The exact amount is hard to measure, though.

No, the issue is whether it is faster / more efficient to climb with the suspension locked out.

The sport is littered with examples where “basic human intuition” was wrong….skinny, high pressure tires, focusing on the weight of bikes, lightweight wheels vs. aero wheels, etc.

No doubt more robust testing is required, but so far, the data indicates that there is no measurable loss in drivetrain efficiency when climbing with active suspension.

Efficient = easier and faster

As for the second point, yes, sometimes things are unintuitive. But more than often, intuition is pretty close to the truth.

What does “drivetrain efficiency” even mean? I don’t think anyone every suggested that changes in suspension geometry was ever affected the bike’s efficiency all that much. Again, the issue is how hard it is to go a given speed.

Yeah… but… requires more power expended by the human rider to generate the same power at the drivetrain.

So if you want to ride fast uphill on a smooth trail at lowest physiological cost, better to ride locked out. That said, suspensions are getting good enough these days where I’d bet the difference is still smaller than what most would think.

The take away from the above videos’ anecdotal “experiments” and limited referenced studies is not that lockout isn’t more effective/efficient. Rather the effeciently is just likely much less so than marketing advertisement, which should come as a surprise to no one. The marginal, lockout efficiency is most likely there it’s just lost in not only the limitations of measuring devices +/- 2% but also the averaging of the data, sample sizes, control groups and durations observed.

One could do the exact same test runs as Dylan/Peak Torque with an additional 1 pound water bottle added to the bike and reach the same conclusions. The power, time and HR would be essentially the same and be statistically insignificant. It is simply the constraints of the limited observations and devices. However we know mathematically and scientifically that adding 1 pound will and has to be less efficient as the grade points up and effort duration increases, holding all other factors constant.


Efficient transfer of energy form the input (pedals / crank) to the output (speed). A minimum loss of energy due to systemic issues, be it friction or suspension movement.

Based on what data?

One of many things in cycling where you can for sure FEEL a difference but the actual delta in performance associated with the feeling is de minimus. So that’s the dissonance & it’s hard to shake. Stiffer cranks, stiffer frames, higher tire pressure…you may definitely feel a difference but in terms of actual performance there is no difference or a negative difference.

Locking out suspension may be the apex of cognitive dissonance. You can definitely, definitely feel a difference. Is there a difference? If there is it’s not measurable.

Ok, so let’s talk about heart rate. The assertion in the video was that there is a ‘clear metabolic difference’ between a locked out shock and an open shock. Really? This is where cognitive dissonance might be working it’s evil magic. Peak Torque started with the hypothesis that locked out is more efficient. Dylan didn’t see that but Peak Torque thought it must be true and Peak Torque is the guy that can get this correct. After investing some intellectual capital in the matter Peak Torque measured no difference…thus the dissonance.

Now comes the confabulation. Look, Peak Torque is a super smart engineer so if he says locked out is more efficient how can it not be? Either Peak Torque’s hypothesis was wrong or he is correct but the difference just can’t be detected…like dark matter or something. So based on Occams Razor it’s clear that the difference DOES exist j ust like Peak Torque says & it’s just impossible to measure.

One thing it definitely CAN NOT BE is that after doing a number of reps at 300W both seated and standing (first locked out then not locked out) as the morning sun climbed in the sky and the road warmed up…one thing it definitely CAN NOT BE is a little heart rate drift caused by natural fatigue of repeated 300W efforts and increasing ambient temperature and possibly a little thirst that accumulated over what Peak Torque told us was a long session of taking data.

Again, based on Occam’s Razor, the most reasonable explanation for that heart rate drift is that the damper of the shock was causing it. Not fatigue or ambient temp increase or thirst. And because of that, Peak Torque’s hypothesis is not only intact, but confirmed! Whew! That was close. High five, Peak Torque!


Does he compare an open shock with a locked
shock while seated? Comparing HR between standing and seated is… not useful. Did I miss it?