Want some more info to drive you crazy?? Or maybe improve the way your tires work & last for you?? Just answer me this - Was that pressure increase after ryding it a bit, or just from sitting still in the garage as the temperature of the day climbed?
The funny thing about tire pressures is that if you want to stop or reduce the pressure increase that generally occurs when you ride, you need to INCREASE their cold/start pressure a little!!
As your tires roll & flex while you drive or ride, the tire tread & carcass gets warmer & the air inside the tire increases in temperature & pressure. You actually need SOME increase in temp & pressure in order to get the tire tread compound up to its ideal operating temperature so it can provide optimum traction & ride etc.... generally, most tire manufacturers recommend that on passenger vehicle tires, you should aim for a 4psi increase after about 30-60 mins of riding/driving.... any more increase than 4psi in that time & the pressure increase is telling you that your cold/starting pressure was too LOW & should be a bit higher cos you are risking tire damage, blow-outs, or tire ply delamination, sloppy handling, increased/abnormal tread wear, & less than ideal ride & traction; while any less than 4psi increase & its telling you your cold/starting pressure was too HIGH & you are risking less than ideal traction & a harsh ride, with a different pattern of increased/abnormal tread wear & an increased chance of punctures due to the inability of the tire to absorb impacts & a bunch of other stuff....
So if those pressure changes occurred after you'd ridden for 20 mins or so, I'd suggest your starting pressures were a touch HIGH for what you are doing/the way you're ryding & you could probably drop them one psi or so before you start ryding next time. But if those pressure changes occured while it was just sitting in the garage & the temp increased as the day progressed, then I'd leave them exactly as they are FOR NOW, and check them again after 30-60 mins or so of ryding!! If they haven't gone up to at least about 24 up front & 32 in the rear, then your initial starting pressures are too high & you should drop them a bit to get the best/ideal traction, ride, and tire life! :thumbup: