The mfg. spec allows for a certain amount of ambient temp change, plus heating up from rolling at speed.
So I don't go tooo far beyond max sidewall when the outside temps are very changeable. I don't know what amount of outdoor temp increase the mfg. assumes they have to allow for - but my guess is that's what we're using when we inflate beyond max sidewall. So if mornings are 40 and I can expect 90 in the p.m. then I won't inflate (in the morning) much beyond max sidewall. By afternoon, before I start my drive home they'll be 5 psi more just from outside temp. If I only expect a change of about 30 deg. then I might go higher than max sidewall.
Right now I'm kinda waiting for the season to stabilize a bit. We've had up and down temps lately but I think it's time to put my 35 psi tires up to about 38-40, measured cold in the morning.
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Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.
Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
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