Tire pressure on the road

[clev]

I have a new Mobile Suites with 215/75R/17.5, G114 tires. Max psi for these is 125 and with 15k pounds on the axles (weighed), I keep them at 125. I also have a tire monitoring system to keep a check on them. I've only towed the trailer 3 times since I picked it up in November, and even in these cool temperatures, the psi increases on each to almost 150 on the highway. I'm concerned that in the summer, here in south Texas, that the psi will increase even more, due to highway heat. Just how much psi will these tires sustain? I've e-mailed this concern to GY with no response. Can anyone here offer any information?

[time2roll]

Check pressure before you roll and before the sun hits them.
Ambient temperature and altitude are all relative and compatible.
If you have a drastic change in climate then check the next morning again.

[golf_bears]

clev, thanks for your thoughts but one is not always someplace which is at 70 degrees. We leave WI after Thanksgiving and it is never 70 degrees, more like in the teens. Left a few years ago and it was about 8 degrees.

[clev]

Golf, pressure should be checked at 70 degrees and then left alone. Adjusting pressure as the temperature or altitude fluctuates is not recommended.

[golf_bears]

Here's a hypothetical, well maybe not so hypothetical. Suppose you are leaving in the morning and the outside temp is 40deg F. You check your tires and find they need to be aired up to 125 psi, so you go ahead and air up to 125 psi. You travel all day then pull over for the night. The next morning you're ready to leave again and the outside temp is now 80deg F. You will most like find that your tire pressure is now higher than 125 psi. So, you now have to let air out to get them back to 125 psi. This is pretty much how it works. That is why all the tire Manufactures suggest you check your tires before leaving and set the psi while they are cold. Doesn't make any difference how hot things get after you set the cold temperature psi. The tires are engineered to withstand high temperatures after being set to the correct psi while they are cold. This is pretty much what I do and have not had any tire problems with about 55,000 miles on the RV tires. So the moral of this story is, check your tire psi before you hit the road and adjust accordingly. Safe travels to all!!!!

[ken_burke]

Hunter11 wrote:
I run the same cold tire pressures as RustyJC in our tires, 120 PSI. We took a trip last July to Oklahoma to see my dad and saw pressures increase to about 145 psi in 100* temps. I don't recall what the tire temps got to but all was fine. I run the TST TPMS.

. . .
We (forum people) do not really know the true answer. So, it seems to me that 110 psi would be a good pressure to use. I use 110 psi on G rated tires, and it work well.
ken

[Hunter11]

I run the same cold tire pressures as RustyJC in our tires, 120 PSI. We took a trip last July to Oklahoma to see my dad and saw pressures increase to about 145 psi in 100* temps. I don't recall what the tire temps got to but all was fine. I run the TST TPMS.

[theoldwizard1]

Lower pressure = higher operating temperature. Higher temp = more wear higher likelihood of failure.

[clev]

A couple of you mentioned the TST tire monitor system, which is what I have. Not liking the screw on sensors, I ordered 4 internal sensors. However, none of the local tire shops could work on tires this big, and would not install them or balance the tires. I called dealerships and C/world but all were backed up for at least 2 weeks. So, I'll keep the externals. The do work well for both psi and temp.

[Cummins12V98]

stripit wrote:
I installed those up graded tires on my 36TK3 when the factory installed the 'G' rated tires. I used to watch the starting pressure grow to 142-146psi no matter if I started at 100, 110 or 120psi. That tire seems to like the higher pressures and stays there no matter what the outside air temps are. I had the TST monitor system to monitor the pressures and temps. The G tires I always ran at 110psi, but the H tire I was able to run at 110 and they held up great as opposed to running them at the 125 max cold.

If 110 was the proper psi with the "G" tires the same psi will apply to the "H" tire.

[stripit]

I installed those up graded tires on my 36TK3 when the factory installed the 'G' rated tires. I used to watch the starting pressure grow to 142-146psi no matter if I started at 100, 110 or 120psi. That tire seems to like the higher pressures and stays there no matter what the outside air temps are. I had the TST monitor system to monitor the pressures and temps. The G tires I always ran at 110psi, but the H tire I was able to run at 110 and they held up great as opposed to running them at the 125 max cold.

[clev]

Good replies. I've always been aware of my tire psi and temps, but my previous 16" tries did not increase so drastically.

[Cummins12V98]

Know your tire weight. Use the inflation/weight chart and add 5psi to what the heaviest tire is. I run 125psi since my axle weights combined are 17,500#. I had the same tires on my 07.5 36SB3 MS and ran 110psi with even wear over thousands of miles and they ran cool.

[tvman44]

That is perfectly normal, that is why the manufacturers say to set your tire pressure cold (ambient temp) because they will heat up when rolling. The same is true on your tow vehicle also or any vehicle (even a car), we are just not aware of it without a TPMS telling us this. I live in S Louisiana & have pretty much the same temps you do and have not had a problem in 10 years of towing, but like you I still worry about it even thou deep down I know it is OK. 🙂

[clev]

Thanks, Rusty. I see that you are also in Texas. The tires are rated at 4805 pounds at max psi. I have not had an opportunity to have individual tires weighed and am basing everything on the weight on the axle. At mid-7's on each, with a carrying capacity of 9610, I suppose that I could deflate down to about ~115~120, and that would have them at ~135~140 psi at highway temps. But that would be in cool weather, less than 80 degrees. What do yours average when Texas temps reach 105?