WoodIsGood wrote:
What is considered an excessive temperature for tires? If I set my tire pressure to 5psi higher than the manufacturer's recommendation, when driving 65mph on a hot day (100+*) the pressure of the rear tires will increase by as much as 30psi (go from 85 to 115psi). At 10 degrees per 2psi increase that's a 150 degree increase in internal tire temperature. Starting at 75* the tires will reach 225* internally! This is true with both the original Goodyear G670RV and new Michelin XRV tires in size 245/70R19.5-F. This seems excessive to me, so I end up running the tires at the max recommended pressure (95psi, or 15psi higher than the chart recommends). This cuts the pressure increase while driving in half, but results in a harsher ride.
I've weighed by coach several times over the years on various truck scales (rear axle always less than 13,000 lbs. with less than 200 lbs. difference side-to-side). I've checked my pressure gauge against 5 other gauges and all were within 1psi of each other. I use a TST TPMS system (interestingly all 10 of the sensors read 3psi lower than all of my gauges at all pressures from 35psi to 115psi.).
Is a 30psi (and corresponding 150*) increase normal and I'm worrying about nothing? The front tires never increase more than 15psi.
Story short, always add a cushion of air for all the variables, no matter what the ambient and I've always added 10 - 15psi over the inflation chart and especially since I only weigh the axles and not all four corners. 5% is usually what's recommended, but don't feel that it's enough and again for all the variables over a long trip. Forget about the pressure increase with heat from the road and not a factor. Unless of course, you've filled the tires to max rating and have exceeded the wheel's rating as well. Even then, I doubt if you'd suffer any immediate damage. Maybe a real rough ride and a bad wear pattern over time.
The real danger, IMO, is to run under-inflated and this will happen if aired up exactly and according to the inflation chart.
Most likely the cause of a lot of blowouts.
