Members who have donated towards server costs
Join Date: May 2006
Location: Tampa, Florida
I think the question is - if I filled the tires when it was 80 degrees out and want to ride when it's 40, do I have to adjust for the temperature difference?
While you should check your tire pressure before every ride, the pressure difference is negligable with the range of temperatures a sane person would ride in.
Quick chemistry lesson...
PV=NRT (T is in kelvins) - P is pressure, V is volume, N is number of molecules (in moles) and T is temperature in Kelvins. Simple algebra will change the formula to P=T/V
30 degrees farenheit = 272 kelvin
100 degrees farenheit = 310 kelvin
I don't feel like working the math, but at 32 psi that gives a pressure drop of about 4 psi (many gauges are only accurate to 2 or 3) and most people don't ride in that wide a temperature range.
All that to say - it's a good idea to check your tire pressure before each ride, but the change in pressure due to temperature is generally negligible. (and yes, the tires will heat up some during a ride making same difference even more negligible).
Ok... gotta run to work...
Using 100F @ 35psi, 10L for vol, .93 moles, calucating for 30F, all other variables remain the same yields 30.6 psi, that is a significant change, worth correcting.
93VN750, under re-construction
vn750.com Member # 828
Rick's Stator and R/R
MF AGM Battery
Shaved & Jetted
MAC Tapered Staggered Pipes
Stainless Steel Brake Lines
23,XXX miles and holding pending gasket change (underway!!!)