I actually did a quick test with 27x2.6 tires in the summer:
With the bike sitting in the July sun for a bit, my infrared thermometer got a surface reading of about ~125F with 19 & 21 psi. A few hours after sitting in the basement, the temp reading dropped to ~70F, and the pressure dropped by ~3 psi to 16 & 18.5. And this tire/rim/tape/sealant/valve combo usually loses only a couple PSI over the course of a week, so over a few hours is was definitely all heat.
A tire with somewhere around 3x the volume is going to drastically change pressure with temp swings from room-temp inside to winter outside. Enjoy the learning!
Feb. 2, 2023, 8:44 a.m. - Justin White
I actually did a quick test with 27x2.6 tires in the summer: With the bike sitting in the July sun for a bit, my infrared thermometer got a surface reading of about ~125F with 19 & 21 psi. A few hours after sitting in the basement, the temp reading dropped to ~70F, and the pressure dropped by ~3 psi to 16 & 18.5. And this tire/rim/tape/sealant/valve combo usually loses only a couple PSI over the course of a week, so over a few hours is was definitely all heat. A tire with somewhere around 3x the volume is going to drastically change pressure with temp swings from room-temp inside to winter outside. Enjoy the learning!