Firestone OEM tires

[RV_Goose]

I'm curious what you meant by this. Did you mean that after towing at 90% rating, your air pressure rose from 90psi cold to 100psi hot? I would think this is normal due to the effects of the Ideal Gas law. It does not take long in driving for the tires to start to warm up, correspondingly heating up the air, where the result must be that pressure will increase as volume remains static while temperature rises.

An example of how important this is relates to my motorcycle road racing (GP style track racing). We use tire warmers to heat our tires as well as heat sinking the rims as much as possible to about 175F. It's at that temp that we set tire pressure, based on our bike, the track conditions, and the specific tire. Even then, after sitting on the grid we then do a "warm up lap" before final grid - for which the purpose is in large part to get some more heat in those tires. Tire warmers are even used on the grid and removed (along with the portable generator, wheel stands, etc) just before they're ready to drop the flag.

So, I would not at all be concerned over a 10 degree F increase in temp from cold after driving even a short distance. But that's just my thought.

In the pic, you can see why tire performance and temps are something I was pretty concerned with.......

Firestone rear tires went from 80 PSI cold, to over 100 with under 6000 on the rear axle. Michelin tires did not do that with the same load, same truck.

I am also used to adjusting motorcycle tire pressures base on % of increase from cold to race temp.

 

[Wmhjr]

Firestone rear tires went from 80 PSI cold, to over 100 with under 6000 on the rear axle. Michelin tires did not do that with the same load, same truck.

I am also used to adjusting motorcycle tire pressures base on % of increase from cold to race temp.

OK, in your previous post you said 90psi to 100psi. Not a big change. Curious what the Michelin tires did and which models. Obviously there will be a pressure increase. There has to be. The only question is how much different that increase was.

 

[H3LZSN1P3R]

OK, in your previous post you said 90psi to 100psi. Not a big change. Curious what the Michelin tires did and which models. Obviously there will be a pressure increase. There has to be. The only question is how much different that increase was.

My coopers only go up 4-5 psi max at full loads

 

[RV_Goose]

OK, in your previous post you said 90psi to 100psi. Not a big change. Curious what the Michelin tires did and which models. Obviously there will be a pressure increase. There has to be. The only question is how much different that increase was.

Michelin never got over 95 on I-95 450 miles NC to FL in June. and usually not that high.

 

[Wmhjr]

Just for kicks, I'll try to remember to check mine. Did you just use the TPMS data or did you actually check with a gauge. I have a trip pulling the GN in a few weeks and if I don't have a senior moment I'll try to see what the stockers do. I do have to say I'm pretty surprised that your Michelins never got over 95 on that stretch of road in June. No matter what tire, I would have expected more than a 5 degree increase. If I have time, I'll do the math. I'll have to try and estimate surface temps and heat increase and volume but then it's just simple math with the ideal gas law. BTW - I am certainly not questioning what you saw. I'm just surprised. Even a typical care tire with low load will see about a 3 degree increase just in normal driving in the first 15 minutes.

 

[RV_Goose]

Just for kicks, I'll try to remember to check mine. Did you just use the TPMS data or did you actually check with a gauge. I have a trip pulling the GN in a few weeks and if I don't have a senior moment I'll try to see what the stockers do. I do have to say I'm pretty surprised that your Michelins never got over 95 on that stretch of road in June. No matter what tire, I would have expected more than a 5 degree increase. If I have time, I'll do the math. I'll have to try and estimate surface temps and heat increase and volume but then it's just simple math with the ideal gas law. BTW - I am certainly not questioning what you saw. I'm just surprised. Even a typical care tire with low load will see about a 3 degree increase just in normal driving in the first 15 minutes.

Apparently I typed in error earlier. I started at 80psi. And the Firestones jumped up to over 100 PSI quickly. The Michelin never got over 95 PSI.