Tire Pressure and Temp

[GABob]

A question for the seasoned folks here..

Went on a trip today, first time in several months. As it has been cold and the unit was sitting for awhile, I had to top off the tires. I’ve got a bunkhouse model, and the bunks are great for storing stuff when traveling. That said, my passenger side likely has a bit more weight to it. I noticed when driving today that the right rear tires were several degrees higher in temp and had a few ponds of increased pressure.

Question: Is this due to weight balance or a tire issue? I run 75/80 tire pressure cold; as they heat up is there a max pressure, temp that I should watch for? I use a TPMS that was set when I purchased it. Haven’t had any alarms but would be good to know. RV is 4 years old with 26K on the tires ( planning on upgrade to the 121s at some point, but figured it’s good to ask in the meantime. Thoughts most appreciated.

[JFlightRisk]

Your tire pressure will drop about one pound for every 10* the temperature drops, and another one to three pounds of loss per month. Tires are porous, just the nature of the rubber.

The added cargo in the bunks will have an effect, as will the sun shining on that side when you're traveling. If you set them to the max pressure, they have a built-in tolerance for the higher pressure when they're warm. They're engineered to take it, so no one has to continuously adjust for warm or cold tires as you drive.

[GABob]

Many thanks, JFilght!

[Marcm157]

I agree with JFlights comments. I always run my trailer tires at max psi cold. I have always noticed a few psi and degree difference on my heavier side..

[LukeDagny]

I had a TPMS system for my TT, and the drivers side tires always were a few psi/degrees higher. I don't know of was weight or the crown of the road, sunny side, or whatever. I came to accept it and never had a problem.

[Bill Johnson]

Originally Posted by GABob

A question for the seasoned folks here..

Went on a trip today, first time in several months. As it has been cold and the unit was sitting for awhile, I had to top off the tires. I’ve got a bunkhouse model, and the bunks are great for storing stuff when traveling. That said, my passenger side likely has a bit more weight to it. I noticed when driving today that the right rear tires were several degrees higher in temp and had a few ponds of increased pressure.

Question: Is this due to weight balance or a tire issue? I run 75/80 tire pressure cold; as they heat up is there a max pressure, temp that I should watch for? I use a TPMS that was set when I purchased it. Haven’t had any alarms but would be good to know. RV is 4 years old with 26K on the tires ( planning on upgrade to the 121s at some point, but figured it’s good to ask in the meantime. Thoughts most appreciated.

My motorhome always has different pressures and temperatures on the tires, they don't very much. They say max is around 195 degrees

[norty1]

My TSPS has a built in high temp alarm for 157 deg f*. I have never seen over 120 deg that I can remember. Mostly lower depending on speed and ambiant temps.

This link states that if properly inflated and not over loaded, temps should not be a cause of tire failure.

https://blog.tiremart.com/how-does-t...ct-your-tires/

[GABob]

Thanks, all. I may have been needlessly concerned; always feel better asking the seasoned professionals. Temps never even hit 100 (highest 95 to 97) but we’re higher than the drivers side. Was concerned why there was a several degree variance from the driver’s side but seems my assumption was correct about the loading. That said, seems the variance is within reason.

[TaftCoach]

After many thousands of miles I just accept that there will be a difference. It did cause me some concern at first as I tried to chase the correct psi. My obsession ended when I asked my wife to move from the front passenger seat to sit in the backseat driver's side to see if it changed the PSI LOL.

[craigav]

Did you know that the weight on a tire doesn't change the PSI in the tire? Perhaps enough weight to deform the tire would cause an increase in PSI. You can tell this by airing up a tire to the recommended psi and then mounting on the vehicle and the psi in the tire will be the same as before being mounted on the vehicle. However, more weight certainly would be more heat while travelling, and the heat would bring up the psi more than when it was cool.

In any case, I like to air up all of my tires just after sunrise, that way they have cooled all night and the sunlight hasn't warmed them up any. With doing that, by mid-afternoon they will not have the same psi driving or parked, but close enough. ~CA

[RogerR]

I did not notice anyone suggesting this so I will. If you have a place to weigh your rig such as a Cat scale or local granary, take it there. Weight the whole rig and then try to weight each side or back side separately. The key to take from this is to make sure you are not overweight in whole or any one axle.

Overweight will over stress tires and cause overheating.

[spoon059]

I notice the tires on the sunny side are often hotter than the tires on the shady side.

[SmokerBill]

Originally Posted by spoon059

I notice the tires on the sunny side are often hotter than the tires on the shady side.

Yep. I usually need to adjust the pressure of my truck tires twice a year, spring and fall. Just before the sun comes up in the morning to get an accurate cold temperature. I just increased the pressure in mine last week, so they'll be good until next spring when the average temps rise.

[pconroy]

Originally Posted by norty1

My TSPS has a built in high temp alarm for 157 deg f*. I have never seen over 120 deg that I can remember. Mostly lower depending on speed and ambiant temps.

We hit 130*F, running thru Arid-zona, mid-summer.

A TPMS is a mixed blessing. Before I had one, I never knew what the temps and pressures were when driving. Now it's something else to look at and worry over.

[tom463219]

Originally Posted by pconroy

We hit 130*F, running thru Arid-zona, mid-summer.

A TPMS is a mixed blessing. Before I had one, I never knew what the temps and pressures were when driving. Now it's something else to look at and worry over.

At those temps what did the pressures go up to?

[pconroy]

Originally Posted by tom463219

At those temps what did the pressures go up to?

90ish.

[Bill Johnson]

Originally Posted by pconroy

We hit 130*F, running thru Arid-zona, mid-summer.

A TPMS is a mixed blessing. Before I had one, I never knew what the temps and pressures were when driving. Now it's something else to look at and worry over.

Well they say it damages the tire around 250 degrees so that wasn't that bad

[tom463219]

Originally Posted by pconroy

90ish.

OK, Thanks. I set the dually's to 80 and i have seen them go to the low 90's in the hot summer.

[billcf7]

This time of year you may need to adjust your cold pressures daily if travelling north and south. Could be 0 deg. one morning and 70 the next which will change your cold pressure by approx. 10-20 psi. Rule of thumb is 2% for every 10 deg F

[foglght]

The tires heat up pretty quickly even in colder temperatures. There is no reason to run them more than 80 hot (with the stock tire saying 80psi cold max).

Rear axle GVWR is 9500lbs and the dually tires (per side) are I believe rated at 4940 (depending on tire) so the total is 9,880lbs which is more than the rear axle should take anyway which would be at the 80PSI.

The charts are for the most part linear from 40-80psi so somewhere between 75-80 psi hot is all one would need.

Same with the front. Its rated at 5k lbs. The tires @ 80psi are rated for 5,360lbs.

If your rig is over GVWR that's a different problem.....

I typically run the tires at 70 cold. Never had an issue. They ride nicer as well.