Do different bikes/geos give you different power profiles on the trainer? I understand obvious extremes like trying to put a kids bike on the trainer and get max output. Probably wouldnt work so well. But what about subtle differences in geo and or positioning? Has anyone toyed with this, or seen differences across their bikes ie your road v mtb?
Ultimately, the goal here would be to try out different frames or suspension tuning to see if there are any major differences before releasing it to the wild.
There are plenty of discussions around. I can search later, but most revolve around stuff like road bike to TT setup or taking a road setup in a more aerodynamic direction.
SUPER SIMPLE SUMMARY: A more extreme forward rotation of the back & hips, lower arms & hands can lead to lower power output. People list stuff like 5-10% lower power on a TT bike vs road bike in many of the cases I’ve read.
Outside of that (ignoring aero) there is potentially a decent range of upper body position that can give similar power levels. Stuff like aero or handling (more relevant to your apparent MTB focus?) could lead to one direction or another.
There is no practical way to evaluate this on a trainer if that is what you are suggesting.
Thank you. That is a good starting point.
Although I do find it hard to believe that rear suspension has no effect on power output. Not that I disagree, but I would assume that one would have to lose some power with a reduction in frame stiffness. If that is not the case… wow!
That is not even close to a proper takeaway from what I said.
Suspension analysis with respect to power production and efficiency is a nasty beast that takes far more to evaluate than locking a bike into a static position and cranking watts. Actually riding outside, even in perfect conditions is still a partial guessing game without A LOT of control of variables and effort to maintain consistency.
I’d point you to the PinkBike XC & DC bike reviews with their time test. They are some of the the best at that process and seeing what it takes them to get that should be eye opening. Much less than that is subjective at best and likely misleading.
There are one or more topics here discussion suspension and lockouts in particular IIRC, and reviewing those would be worth your time.
TLDR, bike testing for power with respect to frame stiffness and/or suspension is not easily done.
I seem to recall reading something about hip angle and power. When you open the hip angle (on a road bike) you lose some aerodynamics so it’s a trade-off.
I have noticed Tour de France riders like Pogacar with a more open hip angle. It also seems to result in a more forward weighted position. Pog though doesn’t need aerodynamics since he can sit on wheels all day until the final climb.
It’s hard to find the right photo but in general he seems to have a fairly upright position for a pro rider.
Sure, makes sense to a point. But that locked in aspect typical of most trainers may well become a variable that is problematic when compared to real world riding use. Even something like a rocker plate could help a bit, but I still question the basic effects in play with a mostly static setup vs true rolling in space.
It may well correlate and be representative, but I sure wouldn’t assume that without some real world testing to cross-validate any trainer results.