The effect of road use on tyre pressures is quite interesting, so today I conducted an experiment. I had to complete quite a long trip - 630 km end-to-end. The attached pic shows this was completed at an average 94kph
Before I set off, I carefully checked and equalized all tyre pressures at 34psi front, 36 psi rear. These were set cold, in an ambient temp of 13C.
I measured them again, just then, at the completion of the drive. The last section of the drive was about 90 minutes at 110kph (GPS, on a heavily policed motorway). Tyre pressures were 35.5psi F, and 36.5psi R. Ambient temp is again 13C, although it was as high as 22C during the trip.
My conclusions:
- in day-to-day driving, ambient temps are as big a factor as road heat, although there is an effect (that's why you should check tyre pressures when there are big changes in ambient temps)
- Front (steering) tyres are more affected...makes sense...more friction, generating heat
- This is quite different to track driving, where there are big frictional effects at both ends, generating heat
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