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 > Tire pressure (temperature) increase while driving

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WoodIsGood

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Posted: 09/13/17 11:09am Link  |  Quote  |  Print  |  Notify Moderator

What is considered an excessive temperature for tires? If I set my tire pressure to 5psi higher than the manufacturer's recommendation, when driving 65mph on a hot day (100+*) the pressure of the rear tires will increase by as much as 30psi (go from 85 to 115psi). At 10 degrees per 2psi increase that's a 150 degree increase in internal tire temperature. Starting at 75* the tires will reach 225* internally! This is true with both the original Goodyear G670RV and new Michelin XRV tires in size 245/70R19.5-F. This seems excessive to me, so I end up running the tires at the max recommended pressure (95psi, or 15psi higher than the chart recommends). This cuts the pressure increase while driving in half, but results in a harsher ride.

I've weighed by coach several times over the years on various truck scales (rear axle always less than 13,000 lbs. with less than 200 lbs. difference side-to-side). I've checked my pressure gauge against 5 other gauges and all were within 1psi of each other. I use a TST TPMS system (interestingly all 10 of the sensors read 3psi lower than all of my gauges at all pressures from 35psi to 115psi.).

Is a 30psi (and corresponding 150*) increase normal and I'm worrying about nothing? The front tires never increase more than 15psi.

Lwiddis

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Posted: 09/13/17 11:11am Link  |  Quote  |  Print  |  Notify Moderator

"If I set my tire pressure to 5psi higher than the manufacturer's recommendation"

Not a wise move unless you are a tire expert. Voids warranty and probably any manufacturer liability.


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SidecarFlip

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Posted: 09/13/17 11:16am Link  |  Quote  |  Print  |  Notify Moderator

First off, never take your tire gauge readings as gospel, almost every gauge will read differently.

Secondly, you always carry more weight on the back axle(s) than the front so tire temperatures and pressures (over cold inflation pressures) will increase more.

Thirdly, I would never increase cold inflation pressure over the sidewall rated maximum inflation pressure. Tires are designed and marked with that pressure for a reason. Tire manufacturers know how much a pressure increase will be and factor that into the tire design.

Finally, as long as you can place your hand on the tire and it don't feel uncomfortable, the tires are fine.


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Chum lee

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Posted: 09/13/17 11:18am Link  |  Quote  |  Print  |  Notify Moderator

30 psi pressure rise seems excessive. Has anyone put some type of "goop" in the tires attempting to fix a flat or balance them out? What does the air inside the tire smell like when you bleed the tires with excess pressure?

When I run my 19.5" G670's at 90 psi cold (18,000 lb. GVWR Ford F53 chassis) the pressure would go up less than 10 psi on a hot day. The actual weight of my RV was usually between 15,670 and 17,000 lbs. Running the tires at 80 psi put excessive wear on the outside edges of the tires so I raised it 10 psi. Under my driving conditions, Goodyear says its OK to do that. The coach manufacturers recommended pressure is 80 psi.

Chum lee

* This post was edited 09/13/17 11:31am by Chum lee *

WoodIsGood

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Posted: 09/13/17 11:36am Link  |  Quote  |  Print  |  Notify Moderator

Forgot to mention, I called Michelin customer service and basically got a "don't worry, be happy" answer. But the rep lost all credibility when he said the air temperature inside the tire has no real relation to the temperature of the rubber.

SidecarFlip

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Posted: 09/13/17 11:43am Link  |  Quote  |  Print  |  Notify Moderator

In reality, I don't unless the air inside is at the ignition temperature of the tire and then it aids in combustion...tire fire.

WoodIsGood

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Posted: 09/13/17 11:51am Link  |  Quote  |  Print  |  Notify Moderator

Chum lee wrote:

30 psi pressure rise seems excessive. Has anyone put some type of "goop" in the tires attempting to fix a flat or balance them out? What does the air inside the tire smell like when you bleed the tires with excess pressure?
Chum lee


No "goop" in the tires. I never bleed air as that would only exacerbate the problem.

Started my last trip with the brand new Michelins at 85psi. On I5 crossing the CA desert at 105* the pressure increased to 115psi. Stopped at a truck stop and added 10psi to each tire (gauged each tire and added 10psi since pressures were dropping as the tires cooled off as I worked my way around the rig). Continued the drive and pressures settled around 110psi. The next morning pressures were 95+/-psi at 75*.

STBRetired

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Posted: 09/13/17 12:30pm Link  |  Quote  |  Print  |  Notify Moderator

I run Michelin XRVs on my MH. Fronts at 90, rears at 94 when cold, which is 3 PSI above what the weight charts say. After driving for several hours at expressway speeds, fronts are 104, rears are 108. So a 14 PSI gain. 30 seems excessive.


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Sandia Man

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Posted: 09/13/17 12:40pm Link  |  Quote  |  Print  |  Notify Moderator

No experience with tires mounted on Class A rigs, but I would imagine that they are engineered to handle the additional temp and psi like truck tires that indeed carry a very heavy load and travel at higher speeds than stated above. At one time we did temp/psi monitoring on tires and hubs at stops along the way, can't remember the last time as it's been awhile.

We do most of our RVing in the four corner states plus TX and Cali, lots of traveling when temps are soaring. No worries, just set psi on all tires (max psi for TT and rear truck tires) first thing in the morning before we head out and let tires perform as designed knowing full well they will increase in both temp and psi which manufacturing engineers have accounted for.

Tyler0215

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Posted: 09/13/17 12:56pm Link  |  Quote  |  Print  |  Notify Moderator

Why did you add more air to the tires?
If the Michelin chart says 85 psi for the weight you are carrying, thats the pressure you should run. Don't be adjusting the pressure when the tires are hot.

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