Tire Pressures Increased

[Toad Haul]

Very strange situation yesterday, thoughts welcome...

So, yesterday I took my Claas C into my local Ford Dealer to have my new DuallyValves installed on my rear tires. Finding a garage to actually do that work was really hard, but that's a whole different thread.

Anyway, MH is brand new for us and after the installation we took it out on a maiden road trip to put some miles on it and have the DW get some road time behind the wheel. When I picked it up from Ford we went home and loaded the doggies for a day on the road. While there I double-checked the pressure in all the tires and put on my TPMS a modules on all the tires. Pressure was dead on 80psi in each tire.

Took off and about 30 miles down the highway my TPMS alert went off showing over-pressure on the right rear outer tire. I pulled over to check the tire and sure enough the pressure reading on the TPMS monitor was right...88psi.

While pulled over, I checked all the tires again and all 4 rear axle tires were at 88psi. What the ? Tires temps were all showing about 70 degrees, so no overheating here.

How did all the tires increase nearly exactly 8 lbs in 30 miles? I've never heard of something like this in 30+yrs of driving. Has anyone ever seen this amount of change? I dropped the pressure back down to 80psi and we put another 300 miles on it with no problems or change in the pressures.

What would cause this? Any help?

[Iron Horse]

It is normal for the tire pressure to increase after driving. I wouldn't let any air out while they are warm, when they cool down they will be underinflated. You may need to reset the tire monitors to reflect this.(High Temp). Driving on under inflated tires will damage the tires.

[Ron_H]

Tire pressure and temperature are closely interlinked and both will increase as your tires roll down the road.

First off, is 80 lb the correct pressure for your tires? The only way to know the correct pressure is to know the weight at each of the four tire positions and reference the weight/pressure chart for that tire.

Secondly, tire pressure can only be accurately measured when the tire is cold (ambient air temp).

Lastly, how are you measuring the tire temperature? Only TPMS with internal tire sensors can accurately measure temps. Those with external sensors are grossly inaccurate as they have no way of sensing the internal temperature.

[Steve Ownby]

Originally Posted by Toad Haul

Very strange situation yesterday, thoughts welcome...



So, yesterday I took my Claas C into my local Ford Dealer to have my new DuallyValves installed on my rear tires. Finding a garage to actually do that work was really hard, but that's a whole different thread.



Anyway, MH is brand new for us and after the installation we took it out on a maiden road trip to put some miles on it and have the DW get some road time behind the wheel. When I picked it up from Ford we went home and loaded the doggies for a day on the road. While there I double-checked the pressure in all the tires and put on my TPMS a modules on all the tires. Pressure was dead on 80psi in each tire.



Took off and about 30 miles down the highway my TPMS alert went off showing over-pressure on the right rear outer tire. I pulled over to check the tire and sure enough the pressure reading on the TPMS monitor was right...88psi.



While pulled over, I checked all the tires again and all 4 rear axle tires were at 88psi. What the ? Tires temps were all showing about 70 degrees, so no overheating here.



How did all the tires increase nearly exactly 8 lbs in 30 miles? I've never heard of something like this in 30+yrs of driving. Has anyone ever seen this amount of change? I dropped the pressure back down to 80psi and we put another 300 miles on it with no problems or change in the pressures.



What would cause this? Any help?

Your tires pressures should always be set cold, that is, before driving? The pressure should be set according to the weight each tire is supporting and using the tire manufacturers inflation table. The temp and pressure will rise when the tire gets up to operating temp. A 10 % increase is not unusual. It's possible the sensors was actually set at a lower psi than the 80 you started driving with. Then should be a procedure to set the base pressure for the TPMS sensor.

Don't ever reduce the pressure when at operating temp. You will be under inflated when cold.


Steve Ownby
Full time since '07

[Dr4Film]

It appears that you are a prime candidate for Tires 101.

Bottom-line, you NEVER let air out of a HOT tire once you have adjusted them to your CIP aims when they were cold.

Read up and study about proper tire maintenance. Here is your first lesson below.

Dr4Film ----- Richard

[Toad Haul]

Well, between comments here and a post on another forum, learned I had set my TPMS alert level at only 10% psi increase. That's supposed to be 20%!

I'll adjust that today and give a big thanks to everyone!

[IdahoSRT10]

If you want more stable tire pressures under all conditions fill with nitrogen instead if air.

[C-PHartley]

Originally Posted by IdahoSRT10

If you want more stable tire pressures under all conditions fill with nitrogen instead if air.

OK. I'll bite. Why is nitrogen more stable than the air we breathe. Normal air is 78% nitrogen and 21% oxygen. Are you saying the oxygen causes instability? Please educate me.


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[IdahoSRT10]

Nitrogen vs Air In Tires - Why Nitrogen in Tires

[Dr4Film]

If you want more stable tire pressures under all conditions fill with nitrogen instead if air.

....true until you need to add some to your tires when traveling and can't find a nitrogen compressor to do the duty.

This is WAY overkill on RV tires. Very suitable for airline tires, race car tires and other specific applications.

Automobile and RV tires not needed.

Dr4Film ----- Richard

[Dutch Star Don]

I'm running helium in my tires and I just float down the road!

[Cobra1]

Not for long as helium leaks right through rubber. Just sayin

[C-PHartley]

Originally Posted by IdahoSRT10

Nitrogen vs Air In Tires - Why Nitrogen in Tires

So are you saying that you have found an RV tire installer that has evacuated all the air out of the tire when mounting the tire, and then fills it with 100% nitrogen, and then removes any humidity? If so, please identify that installer. It has been my experience that most simply fill the newly mounted tire with Nitrogen and call it good. And if you find a low tire while out on the road somewhere, you will have to find someone with high pressure nitrogen to fill your tire. Sorry, but I don't see the benefit here.


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[Steve Ownby]

Originally Posted by Dutch Star Don

I'm running helium in my tires and I just float down the road!

Don, you da man!


Steve Ownby
Full time since '07