TPMS and Tire Pressure

[BarnicleBill]

Relatively new RV owner with a 2016 Newmar Bay Star 3124. I just purchased a Tire Minder TM-77 TPMS and installed it without issue. However, during a run up to Nashville and back (180 mi) I was somewhat surprised at the increase in tire pressures from cold to road temp. I have Michelin 235/80R 22.5G tires with 110 psi max and based on the loaded weight am running 90 psi in the front and 95 psi in the rear (cold). At operating temp the fronts increased from 90 to 99 psi (10%) and the rears from 95 to 108 psi (14%). No alarm sounded so I am assuming this increase is within normal ranges. For those of you who run a TPMS, are those increases what you would consider "typical/normal?"

[aether_one]

Originally Posted by BarnicleBill

Relatively new RV owner with a 2016 Newmar Bay Star 3124. I just purchased a Tire Minder TM-77 TPMS and installed it without issue. However, during a run up to Nashville and back (180 mi) I was somewhat surprised at the increase in tire pressures from cold to road temp. I have Michelin 235/80R 22.5G tires with 110 psi max and based on the loaded weight am running 90 psi in the front and 95 psi in the rear (cold). At operating temp the fronts increased from 90 to 99 psi (10%) and the rears from 95 to 108 psi (14%). No alarm sounded so I am assuming this increase is within normal ranges. For those of you who run a TPMS, are those increases what you would consider "typical/normal?"

The alarm only sounds if you exceed the alarm setpoint that you were supposed to set: I believe they recommend a 20% increase for the alarm setpoint. Your increase is well within the range of normal in my experience.

[Mr_D]

Not a problem. My Pressure Pro has an algorithm built in that figures it for me.

[Brian Lee]

Thats good, i have a jayco 26xd and we pull an 18ft trailer with 2utv’s on it. Only time my alarm has ever gone off is when we were comming down around the north rim of the grand canyon i believe it was an 8% grade and i had a semi right in my tail, guess i was riding the brakes because my pass inbd rear tire went over the temp. Got down on flat ground and let it cool down, never has happened again in a year. I feel these systems are great piece of mind when rolling down the highways

[GreaTOne65]

That's why I disconnected the TPM I bought, it created more questions, and worries. I opted for Accu Pressure valve caps that show if the pressure is right, every time I stop for potty break, I walk around the coach and check for leaks and the valve caps for correct pressures. If you are running the correct pressure printed on the tire, and that pressure is maintained, heat means nothing.

[pdeinc]

Today as we were heading to Tampa, my TPMS alarm went off and I saw that one of the left rears was losing air rapidly. We got off the interstate at the next exit and limped the 30 miles back home, watching to the remaining tire temp and pressure to keep it within range. Once home, I pulled the tire off and found that the problem was a simply a leaking valve stem.

So that's twice in 6 months my TPMS has saved us from being broken down on some highway with damaged tires. No walking around the vehicle at each stop would have helped in either case. And BTW, I was running 75 and couldn't tell a tire was going flat.

[Lt Dan]

The pressure rise is perfectly normal as the tire heats up and gas expands as it warms. I run 105psi in our front tires and have seen it increase to 119-120, especially on hot days. The max pressure listed on a tire is the "cold" setting and they are designed to withstand rises in pressure with temperature. You can also see differences in pressure from the sunny side of the coach to the side in shade.

[Wundertaker]

Originally Posted by GreaTOne65

That's why I disconnected the TPM I bought, it created more questions, and worries. I opted for Accu Pressure valve caps that show if the pressure is right, every time I stop for potty break, I walk around the coach and check for leaks and the valve caps for correct pressures. If you are running the correct pressure printed on the tire, and that pressure is maintained, heat means nothing.

Ok......not a real good move! You are making a lot of bad assumptions that you can't verify while you're sitting behind the wheel going 70 mph.

That's 'nuff!

[xrated]

Originally Posted by Wundertaker

Ok......not a real good move! You are making a lot of bad assumptions that you can't verify while you're sitting behind the wheel going 70 mph.

That's 'nuff!

I agree ^^^^ It's hard to see what is going on with tires/pressures/temperatures when you're behind the wheel driving.

[GreaTOne65]

I didn't figure I'd make to many friends, with my post. But I can tell you if you know your pressures before you start and check them on every stop, with the valve caps, from Accu-Pressure, if you have a tire going down you will have plenty of time to rectify it. The only time you will ever experience a blow out, is if you don't use the pressure branded on the tire. It's a fools errand to let air out of the tires to fix a rough road, and there are damned few good roads in this country. This may not be the way you do it, but it is the way I do it, to each his own.

[Arch Hoagland]

Originally Posted by pdeinc

Today as we were heading to Tampa, my TPMS alarm went off and I saw that one of the left rears was losing air rapidly. We got off the interstate at the next exit and limped the 30 miles back home, watching to the remaining tire temp and pressure to keep it within range. Once home, I pulled the tire off and found that the problem was a simply a leaking valve stem.

So that's twice in 6 months my TPMS has saved us from being broken down on some highway with damaged tires. No walking around the vehicle at each stop would have helped in either case. And BTW, I was running 75 and couldn't tell a tire was going flat.

You mentioned a leaking valve stem for causing one problem.

What caused the other loss of air?

[Mark_K5LXP]

Originally Posted by GreaTOne65

if you have a tire going down you will have plenty of time to rectify it.

You've never picked up a nail or a screw under way? Doesn't happen often but it's happened often enough in my lifetime I'm thankful TPMS's exist, and I carry a plug kit.

Whether it's a nail, a wonky valve stem or a heat issue from brakes, I want to know about it. Ignorant bliss only carries you so far.

Mark B.
Albuquerque, NM

[pdeinc]

Originally Posted by Arch Hoagland

You mentioned a leaking valve stem for causing one problem.

What caused the other loss of air?

One blade of a broken pair of scissors flipped up from the left front tire and pierced the outer rear tire, then flung off and sticking into the fender well liner where the tire tech found it while removing the tire!

I knew exactly when it happened as I had moved over to the left slightly for a car broken down on the shoulder and heard a noise as my tires rode down the centerline stripes.

Again, it wasn't a blowout and the pressure was dropping slow enough that I would not have noticed and my opinion based on over a million miles of driving a semi-truck, the next thing would have been the remaining tire heating up to a point of failure.

[indymeesh]

Just had the exact same thing happen - 300 mile trip to Iowa - 90 degrees out. Class C 31footer. New Tire Minder system - first time I used one. I added 5 pounds to front and back before we left because we had 5 people. Will not do that again.


Set the TTM base line at regular PSI, Wasn't 2 hours and alarms going off - pressure went from 85 to 96 (one went to 102 PSI) 20% over my baseline of 80. Temps also increased a lot.


Reading threads today it looks like I should just always set the tires at the sticker recommended PSI since it is going to go up that much (10 pounds) anyway. I never knew it would increase that much until I had the TTM installed.


Note - got home - now cold - all tires are back to my original settings of PSI.