The loss can be measured, assuming that both power metering devices are “precise” not necessarily “accurate”. Run the same efforts both locked (closed damper) and unlocked (open damper). Could do multiple intervals at 100w, 200w, 300w (as high as you want, I might pick a 100w recovery ride, and randomly select 10 segments, and compare), at 120 seconds a piece, and trim out the first/last 30 seconds as the system is stabilizing to remove artifacts). pick a set cadence for target (do not change it for the entire experiment), and let the erg meter handle the undulations of cadence. EVERYTHING should be the same, except the locked/unlocked. If one thinks that the grade needs to be simulated, prop up the front wheel.
I might do this, if the right workout pops up for me. I am not expecting much to be measured, if any. Suspension travels in a single direction, with very tight tolerances, it doesn’t “deform” the way a tire does, so the losses to “squish” should be much less. The friction and compressive heat loss are probably minimal at best, statistically significant yes (if one can measure it), but substantial most likely not.
To prove/disprove the hypothesis that unlocked takes a higher physiological power output, you also need to include a measurement of how hard the riders body is working.
PT indicates expired gas analysis would be the gold standard here, but that’s not easy to come by. I think with enough runs in the appropriate (randomized) order, heart rate would suffice.
I think modern suspensions are so good, the difference will be reasonably small. FWIW, the biggest difference in physiological toll is likely when you are out of the saddle with fully unlocked front and rear suspension. That would require activation of additional core and upper body muscles to keep stable enough to transfer power to the pedals. Hence the higher physiological toll.
Yes. But what is not clear, is if this energy would otherwise go towards turning the cranks. If it was obvious, and easy to quantify, there would be no need for all those studies!
That energy might otherwise go to elastic deformation of frame, cranks, wheels and so on. Not to mention deformation of the tires.
If you do a track stand on your full suspension and do several preloads, the shock will heat up. No forward movement. You can do the same on a rigid bike. No forward movement. So just because energy is dissipated does not mean that propulsion is lost.
Yes, but do that on a rigid bike and you convert the mechanical energy into potential energy that can be stored for when the forward motion requires it.
I think that this is really the result of the videos on this - if there is a significant inefficiency with unlocked shocks, it is metabolic, and not mechanical.
Not sure what the bound for ‘significant’ is, but from both the tests done it looks like whatever difference there may be in mechanical inefficiency is below the measurement accuracy of the tests.
Maybe, maybe not…as noted above, all the tests were conducted at a relatively low power level…250 for Dylan and 300 (IIRC) for PT. I think more testing is required at higher power levels, although likely for shorter durations. When more power is applied to the system, inefficiencies may emerge.
First, that’s only in “classical physics”. In the real world, there are always losses, particularly in deformation of a rubber tire. So only a portion of that energy is stored.
Second that energy is not stored for “forward motion”, that force you put in is a vertical load. You will only convert it to forward motion if you are pumping the backside of a roller. The energy is “released” as soon as the downward force becomes zero. That energy can be very useful if doing a bunny jump, not so much for propulsion.
This perfectly illustrates what I wrote earlier: in a track stand you and your body expend energy even though essentially none goes towards propulsion. So the efficiency, the share of energy used towards propulsion relative to the total energy your body uses, is close to 0.
Your power meter only measures the share of energy used for propulsion, which is why 300 W at the cranks is 300 W, and if aerodynamics don’t change appreciably, you will go at the same speed.
However, the physiological cost is total energy expended, not the energy at the cranks. So keeping your shocks locked out will be more efficient on a sufficiently smooth surface.
I’m a physicist and Peak Torque is an applied physicist aka an engineer. To us it is so obvious that no study is needed. Still, we shouldn’t assume it is obvious to others and small experiments like this nicely illustrate basic physical principles.
I agree with everything you’re saying. But I think it still remains an open question if all the force going through the frame/cranks of a bicycle is spent turning the crank. I think that’s the interesting part of these experiments.
For instance there could just be “extra” force applied to the pedal at the bottom dead center. That force would not contribute to rotating the crank and so on. Movement of the riders body/change in weight distribution is another avenue that would compress the fork & shock, but likely not contribute to forward motion.
Even if you don’t validate heart rate data as an accurate measurement. I would at least expect it to show a difference if the physiological expenditure was vastly different. So while there might be small nuances between locked out and open, they don’t appear to be large.
Maybe so small, that you overall would be better off with it open, as the physiological toll of riding for hours on an uneven surface is high.
You should not think about force, but energy, or its time derivative, which is power.
Instead, you should start with an energy balance and think carefully where in that chain the power meter sits.
The reason why a bike with open shocks is less efficient on smooth ground is simple: you convert energy generated by your muscles into heat. This share of the energy is not seen by your cranks. So if you keep the energy that arrives at the cranks the same, your body has to generate more energy in total.
Why would you expect a vast difference? Bicycle suspensions are designed to be as efficient as possible when pedaling, not least because pedal bob is also disruptive when you want to achieve optimal suspension performance.
However, the climbs were short and heart rate does not scale linearly with power. So we should be careful to infer from small difference in heart rate how small the differences in total power (i. e. not just the power that arrives at the cranks, but the power your body produces so that a certain wattage arrives at the cranks).
Like I said, it is only a proxy and this was a short experiment with a very low number of repetitions. But I’d still say that this is consistent with what we would expect. It is not just common sense, we know the mechanism and can give lower bounds on the extra energy required.
A proper experiment that can measure total energy expenditure via e. g. measuring gas exchange would resolve that, but isn’t practical.
Basically your FTP/CP will be lower with an open suspension, because it is less efficient as a whole system. This is going to be hard to demonstrate with a single individual… it would be great if someone made a study on this.
It was “common sense” that narrower tires pumped up to high PSI were faster and that lighter bikes were the key to climbing faster.
It has been accepted / common sense that climbing w/ suspension locked out was more efficient…until the data starts to indicate that it isn’t any different.
I have no idea what the actual answer is….but the limited data indicates that our dogma on locking out suspension may have been wrong.
