Road tire pressure

so i did a short test today a 13 min loop done twice. i’m 66.5kg
run 1:
vitus vitesse (rim brake @7kg ish) running 25mm tubeless gp5000 @ <60 psi (maybe). 38mm rims.

run 2:
giant tcr (disc @ 7.2kg ish) also 25mm gp5000 @ 68psi. 50mm rims. 216 watts av 216 np.

i did both runs as closely in method, gears etc as possible. both bike are waxed chains, hambini bb’s and very close in fit. There’s either Aero differences of the lower tire psi is accounting for 12 sec (a lot) of difference. i did verify the giant psi but the vitus may have been lower than 60 psi. could this be? the vitus is about 6 yrs old and the giant < 1 year.

different assiomas on both bikes for power btw, but 12 secs?

Signal or noise? There are quite a few variables that could go into explaining the less than 2% difference in performance. Could also be multiple variables.

I’d guess, that even doing the ride twice on same bike would yield (small) time differences. I wouldn’t feel comfortable concluding much based on your test.

possibly noise. however, i did start the loop off in the same gear ratio, changed gear similarly and had the same av cadence and very close heary rate max. the max power on each run was about 3 watts apart @ at 277 watts i believe. 12 secs is about 100m or more over that time, and it seems like a lot.
could tire pressure (rough slightly undulating roads roads tbh) make 12 secs of difference.
i did a 2 hour endurance ride on wednesday on the vitus and was surprised at the av speed i carried on regular roads.


No kidding. That small of a difference could just a long fart that provided some tailwind


To me it seems like next to nothing in the context of your test. I’m not sure your test conditions would even have the resolution to measure a 12 second difference (1.5%).

Not enough data to make any determination……you need to make a series of runs with both configurations to see if there is any performance difference.

One run of each leaves way too many variables.

gonna start smashing a bowl of chili before my KOM hunts…

I would also guess some decrease in performance would happen from fatigue. Unless you are holding back a lot