Tire PSI?

**kizler** · 06-09-2022, 05:17 PM

I have always thought it best to try to match load and pressure, and then expect 25% increase and 10% decrease as "acceptable" while you travel.

**ajg617** · 06-09-2022, 05:32 PM

Originally Posted by SGT ROC

I run at the pressure listed on the tire for a couple of reasons. After reading many threads on the subject, along with the normally accompanying links to tire experts, I find that at that pressure I am doing no harm. Too low causes flex in the sidewall, thus heat, which can ruin the tires. My tires will never be worn out before they will need to be replaced simply based on the date code on the tires. I will run them beyond the date code, but not a lot beyond. The tires are generally engineered to take over inflation to a fairly high point, mainly caused by heat and altitude. Also, they should be checked and filled when cold, at ambient temp, ideally at 70 degrees. My 2 cents, which means absolutely nothing except to me...

FWIW, on this trip (3700 miles so far and temps ranging from low 40s to mid 90s), I've reset the tire pressure three times to the 125PSI on the placard early AM. This is also based on Cooper's recommendations for setting the max/min pressure and max temp for the TPMS (quote below for the Cooper H tires). The temperature of the tires has maxed out at 110F - that while stopped in fuel line. The max PSI for any of the tires so far has been 148 and each day the individual tire that is highest is a different one which makes me believe road condition/surface has as much to do with the temp increase. So I've been close to the +20% PSI Cooper recommends setting my TPMS thresholds to and that was highway in the mid-to-upper 80s temp.

"The RV trailer should have a placard on it that states what the tires should be inflated to. The max / min pressure should be +/- 20% of that number. Cooper would recommend a max temperature of 180F. The inflation pressure should be set at the placard specified pressure. If there are large changes in ambient temperature, the inflation pressure should be reset to the target inflation pressure at the current morning ambient temperature.
This came from our Radial Medium Truck department for you."

**SGT ROC** · 06-10-2022, 06:22 AM

Originally Posted by ajg617

FWIW, on this trip (3700 miles so far and temps ranging from low 40s to mid 90s), I've reset the tire pressure three times to the 125PSI on the placard early AM. This is also based on Cooper's recommendations for setting the max/min pressure and max temp for the TPMS (quote below for the Cooper H tires). The temperature of the tires has maxed out at 110F - that while stopped in fuel line. The max PSI for any of the tires so far has been 148 and each day the individual tire that is highest is a different one which makes me believe road condition/surface has as much to do with the temp increase. So I've been close to the +20% PSI Cooper recommends setting my TPMS thresholds to and that was highway in the mid-to-upper 80s temp.

"The RV trailer should have a placard on it that states what the tires should be inflated to. The max / min pressure should be +/- 20% of that number. Cooper would recommend a max temperature of 180F. The inflation pressure should be set at the placard specified pressure. If there are large changes in ambient temperature, the inflation pressure should be reset to the target inflation pressure at the current morning ambient temperature.
This came from our Radial Medium Truck department for you."

In my case the placard on the rig matches the pressure listed on the tires. There are so many differing (and similar) suggestions and recommendations I guess its just a matter of following the one you like best. I will say that 180 degrees is very high.

**ajg617** · 06-10-2022, 06:41 AM

Originally Posted by SGT ROC

In my case the placard on the rig matches the pressure listed on the tires. There are so many differing (and similar) suggestions and recommendations I guess its just a matter of following the one you like best. I will say that 180 degrees is very high.

I thought it was very high also - but that came directly from Cooper. I have it set to 110 but I can see it going higher if I were in 100F weather.

Interesting - temps in the mid 80s early AM yesterday in NC and all the tires were 126F. Dropped the pressure 1 lb to 125. This morning in Shenandoah Valley, temps are mid 50s and my alarms of low pressure are going off for all four tires (121PSI and I've set a thresh hold drop of 122). 5PSI difference for a 30 degree drop in overnight temp.

**USA in a Chevrolet** · 06-10-2022, 07:48 AM

Originally Posted by Second Chance

If you know your actual weight per wheel (not guessing, but individual wheel weights with a scale), you can find your tire manufacturer's load/inflation chart and follow that.

Rob

I agree 100%. Over inflating your tires means a stiffer ride & that stresses frame, Bounces around everything in the trailer & wears out the crown in the tire thread. Under inflation is even worse as your tires can fail. If you don’t want to get each wheel position weighed then at least go to a truck scale & get each axle weighed. As an example if your axle weighs 6500 lbs you can safely assume that one side weighs no more than 25% more than the other. That would mean one wheel at 4000 & one at 2500. I have weighed each of my wheels & never saw a difference of more than 300 lbs though. If you want to be safe inflate the tires to the extreme of 4000 lbs according to the inflation load table for your tires. It’s true that there are lots of tire failures but there’s also lots of frame failures from running rough roads. Your tires are designed to flex. If they are over inflated they will not flex. That’s just my opinion after 17 years of averaging 10000 miles a year towing with only one tire failure & that was from a leaking tire in the few years I didn’t use tire monitoring systems.

**timelinex** · 06-10-2022, 11:33 AM

To be clear... I am not worried about PSI for tire longevity. I plan on changing these bad boys within a year or two regardless of wear.

My concern is that it's not even as hot as it's gonna get this summer and my tires already go nearly 20% over max psi. I don't want a blow out, seperation, or some other thing to happen because of too high of PSI.

**JKellerJr** · 06-10-2022, 11:39 AM

Originally Posted by timelinex

To be clear... I am not worried about PSI for tire longevity. I plan on changing these bad boys within a year or two regardless of wear.

My concern is that it's not even as hot as it's gonna get this summer and my tires already go nearly 20% over max psi. I don't want a blow out, seperation, or some other thing to happen because of too high of PSI.

Your not over max PSI. The max setting is a cold (not after they have been run for awhile) setting. They will go over that when running. Everything is functioning normally and as engineered

**timelinex** · 06-10-2022, 11:45 AM

Originally Posted by JKellerJr

Your not over max PSI. The max setting is a cold (not after they have been run for awhile) setting. They will go over that when running. Everything is functioning normally and as engineered

Yes, I fully understand that. It should have all been implied and assumed in the post based on previous posts in this same thread.

There is some absolute "max psi".... and that max psi has some relation to the cold max psi (% over cold max psi).... I have commonly read that the max psi where things may start going wrong with the tire is 20-25% over max cold psi. Currently I am flirting with that lowering bound.

**SGT ROC** · 06-10-2022, 05:07 PM

Originally Posted by timelinex

Yes, I fully understand that. It should have all been implied and assumed in the post based on previous posts in this same thread.

There is some absolute "max psi".... and that max psi has some relation to the cold max psi (% over cold max psi).... I have commonly read that the max psi where things may start going wrong with the tire is 20-25% over max cold psi. Currently I am flirting with that lowering bound.

So what you're saying is that if your max pressure is 100 psi, at 125 you're over pressure? That is not at all true based on everything I have read, and I have read a lot on the subject. Here is a pretty good explanation of what you should do. Note, I did not and do not rely on this only. I have read more on the subject, this just, to me, seems to make sense and is what I follow. https://www.rvtiresafety.net/search/...ax%20Inflation https://www.rvtiresafety.net/search/...ax%20Inflation. There is also this, although not as detailed https://www.bigotires.com/resources/all-about-tires.

**huntindog** · 06-11-2022, 02:44 AM

Originally Posted by timelinex

Yes, I fully understand that. It should have all been implied and assumed in the post based on previous posts in this same thread.

There is some absolute "max psi".... and that max psi has some relation to the cold max psi (% over cold max psi).... I have commonly read that the max psi where things may start going wrong with the tire is 20-25% over max cold psi. Currently I am flirting with that lowering bound.

Tires are made with heat and they come apart with heat. Heat kills tires. Lowering the pressure increases the heat they will run at.... All these other concerns such as treadwear, ride, etc are secondadry to keeping the tires healthy.