Skip to content

Doing testing on how stiffness/weight effect rider times

Viewing 8 posts - 1 through 8 (of 8 total)
  • #93716

    Hey Guys;

    I’m in the process of planing a study on how weight and stiffness effect rider times when climbing. Basically I plan to go up and down the same climb with different weights attached to the bike. I also plan to test crank stiffness effects this time if budget allows (use crank with different stiffness attachments)

    I would like some people’s opinions on this testing, my variables are:

    Temperature, Wind Direction

    Controlled: Tire Pressure, bike configuration, power output

    Dependent: Rider time

    Independent: bicycle weight (Test set 1), Crank stiffness (Test set 2)

    so, what are people’s opinions on this?


    Weight is easier to calculate mathematically – check out

    I like the general idea, but for test set 1 I do wonder what you’re trying to find out. Heavier is slower uphill. Am I missing something?

    Test set 2 would be very interesting, IME. I’m not sure how exactly you’re planing on testing that, but I hope you can.

    "Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.

    Hey Ypsylon;

    Test two will be done with a crank from Ted Camillo, he says he can make a crank with different “tubes” for different stiffness values.

    and with test 1 I just wanted to see how MUCH slower, is the decrease exponential, is it linear? etc. etc. although yes, I should be slower.


    In regards to stiffness, interesting discussion between djconnel

    ” I suspect the vast majority of deflection energy ends up being dissipated propulsively.”

    and Jason Krantz

    ” It turns out that even if we assume all the energy is lost, the losses are still very small. We’re talking about ~1.6 watts’ difference* between the stiffest and most flexible cranks. In my opinion, it’s not worth worrying about. More to the point, it would be very hard to measure in the real world.

    That said, if you can think of a way to measure propulsion from crank spring-back, I’m all ears! :)


    * That’s 1.6 watts at 300 watts total output.”about the impact crank stiffness has…”

    in the latest Crank review…

    Haven’t posted on this in a while, but starting to get this project underway :D

    My plan is to keep my power output consistent (using a powermeter to check) and going up a local climb. I’ll look to time my efforts and repeating this test over several days, taking an average over the days. I’ll be testing the different stiffnesses one after the other to try and control variables like wind and humidity. Obviously things like windspeed and humidity can’t be controlled, but I’ll look to take that info into account by getting the local weather station’s data.

    I acknowledge that many opinions (which I respect) believe that the energy used to flex the crank will be dissipated propulsively, however I want to check if the conversion is 100%.

    If the conversion is very close to 100%, say only 1.6% is lost. I can see the issue of the times being so close that the fluctuation would be due to other factors. However this is an acceptable result for me.

    Any other suggestions?


    … and with test 1 I just wanted to see how MUCH slower, is the decrease exponential, is it linear? etc. etc.

    Actually, it’s Pi-dratic, i.e, it goes as the Pi power of the ratio of mass. So for example, if the mass doubles, then you would be 2^Pi, i.e, 8.82 times slower.


    lol, you got my hopes up hammertime… I was really hoping there would be some relation that I could model. Will find out I guess :D

Viewing 8 posts - 1 through 8 (of 8 total)

Log in to reply to this topic. Don't have an account? Register Here