Tire pressure

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Gary RV_Wizard

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The problem with doing anything to a warm tire psi is that you don't have a clue how much the psi changed since it was cold. That makes it pure guesswork as to how much to let out. If any. If I saw a tire psi that was 50% over what the cold pressure should be, I could justify letting some out. Maybe even 35%. But not much less than that.
 

Babe2201

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The problem with doing anything to a warm tire psi is that you don't have a clue how much the psi changed since it was cold. That makes it pure guesswork as to how much to let out. If any. If I saw a tire psi that was 50% over what the cold pressure should be, I could justify letting some out. Maybe even 35%. But not much less than that.
I have seen tires that are double what they are supposed to be. From what I have seen is that it is less than 15% increase in normal driving.
 

Gary RV_Wizard

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I had set my high pressure alarm at 100 and hoped it wouldn’t be going off all the time.
There is no specified max pressure for any tire and no predetermined psi overage factor for a TPMS. You should set the alarm to be at whatever pressure doesn't routinely alarm in hot weather. In other words, whatever is normal for your vehicle and travel. The idea of an high pressure alarm is to warn you if something really unusual is happening, e.g. a dragging brake or failed wheel bearing (they both cause excessive heat that gets transferred to the tire). The tire itself won't cause that warning unless you badly overinflated it when cold.
 

Domo

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So if you are talking about setting air pressure it is one thing but you said to NEVER let air out of a hot tire. Quite often I have customers that have put way too much pressure in their tires and when I check them I have to take some out and when we have to let air out of them to change them as well.

FWIW you can check and set them when they are warm as well. It is best to do them when they are cold but can be done by adding a little bit for them being warm. It would be a good idea to check them and adjust them at a later time when they are cool but not everybody has a compressor at their house.
On many forums it can be assumed that there are many complete novices that will read out sage commentaries. Many contributors do post opinions that have some generalities stated as ironclad - such as "Never Let Air Out Of A Hot Tire."

As a professional, and for our seasoned members, we understand that letting 1-2 pounds out of a hot tire is probably not going to result in a seriously under-inflated condition the next morning at ambient temperature. We also understand the effects and can assume that responsibility.

Yes, it is possible and sometimes advisable to let air out of the hot tire - but, is it the best procedure we can share with newbies? Perhaps not.
 

PJ Stough

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The steer tires on our coach are set at 110 psi, exactly what the load chart says for the weight they carry. On the highway at 65-70 mph in ambient temps of 85 to 90 degrees F, the pressure will rise to 126. Totally normal.

You should never let air out of a hot tire.
Why should you never let air out of a hot tire?
 

Babe2201

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On many forums it can be assumed that there are many complete novices that will read out sage commentaries. Many contributors do post opinions that have some generalities stated as ironclad - such as "Never Let Air Out Of A Hot Tire."

As a professional, and for our seasoned members, we understand that letting 1-2 pounds out of a hot tire is probably not going to result in a seriously under-inflated condition the next morning at ambient temperature. We also understand the effects and can assume that responsibility.

Yes, it is possible and sometimes advisable to let air out of the hot tire - but, is it the best procedure we can share with newbies? Perhaps not.
Point taken but the way it was posted it was like you might lose a finger or your whole hand if you did it.
 

Babe2201

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I have found in my experience that you are better off staying close to what the vehicle recommends and depending on how much weight is in it maybe even less. I have found that if you go more it can lead to the tire wearing out in the center of the tread quicker.
 

Ray-IN

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I have found in my experience that you are better off staying close to what the vehicle recommends and depending on how much weight is in it maybe even less. I have found that if you go more it can lead to the tire wearing out in the center of the tread quicker.
Ever heard of an over-inflated tire blowout? The vast majority of sudden tire failures are the result of overloaded/underinflated tires.
 

Onyrlef

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Ever heard of an over-inflated tire blowout? The vast majority of sudden tire failures are the result of overloaded/underinflated tires.
That being of course due to friction, underinflated and/or overloaded tires have a larger patch ( the area of the tire in contact with the road surface). The larger the patch the more heat is generated by friction. That's why you never hear of an over inflated tire blow out. For one, most portable compressors would struggle to over inflate an RV tire, most garages/tire stores don't employ idiots, and even then a slightly over inflated tire has a smaller patch.
 

tlmgcamp

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Not a tire expert but I think there may be different answers to tire pressure if we are dealing with a MH or trailer. I understand with vehicles (motorhomes) pressure is a function of performance and comfort. I remember back in the 90s that Ford was battling with a rollover issue with the Explorer and recommend lower tire pressures to settle it down. I would imagine a ride difference with harder tires due to higher pressures. On the other hand I was told that trailer tires should always be topped off at their max pressure
 

John From Detroit

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The proper pressure is the lowest pressure at which the full tread contacts the road (What someone up thread called patch) Too high a pressure and only the inner tread makes contact.. Too low and only the outer edges.
Also too high and less heat is needed to increase pressure to the point of BOOM (heard one of those Saturday.. Some distance from where I was) Too low and the sidewalls flex too much and get "Soft" and BOOM.
So the proper pressure depends on how much weight THAT TIRE is carrying.
For motor homes this is very important.. Trailers... Well technically same but not quite as bad.
 

Ray-IN

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Not a tire expert but I think there may be different answers to tire pressure if we are dealing with a MH or trailer. I understand with vehicles (motorhomes) pressure is a function of performance and comfort. I remember back in the 90s that Ford was battling with a rollover issue with the Explorer and recommend lower tire pressures to settle it down. I would imagine a ride difference with harder tires due to higher pressures. On the other hand I was told that trailer tires should always be topped off at their max pressure
Comfort is not a function, it's felt, and does not affect tire performance. Every MH tire failure thread that's been posted, I've asked about tire pressure habits, very few have admitted to running the absolute minimum tire pressure as indicated in load/inflation charts. Which of course means the tire is operating at 100% capacity continually.
 

RNS

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The manufacturers have ran thousands/millions of miles when they come up with the number on the placard so that is what I go by.

AND don't run winter air in your tires in the summer. I change mine out every spring.
 

Gary RV_Wizard

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Not a tire expert but I think there may be different answers to tire pressure if we are dealing with a MH or trailer. I understand with vehicles (motorhomes) pressure is a function of performance and comfort.
The motorhome manufacturer's psi recommendation is strictly about performance (safety & reliability). The manufacturer recommends a psi that will adequately support a fully loaded motorhome. The psi the owner chooses may be further influenced by comfort and convenience. A knowledgeable owner won't let comfort & convenience influence a choice less than the safe performance minimum, but many owners lack the understanding to do that (or simply ignore it).
 

oldryder

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TPMS was real interesting. I noticed a couple of pounds difference in increase on the tires on the sunlit side of the coach vs. the other. Also had one inside rear tire that always went up a little more than the rest. turns out it was closest to the exhaust pipe. Took a while to get used to how much the pressure changes from cold to warmed up but very reassuring to have the monitoring system.
 

Ray-IN

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I wonder what drivers found to worry about before the invention of a TPMS? Tire and air pressure relationships have not changed since the invention of balloon tires.
 

Mark_K5LXP

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Before TPMS you filled your tires to some nominal pressure (usually what the door jamb sticker said) and off you went, likely months before you checked it again if you checked it at all. Probably didn't get attention unless something was evidently wrong. Gee that tire looks low. Who knows how long you'd go that way before noticing.

Post-TMPS now I see one tire is a PSI higher or running warmer than the others. Kinda like a man with 2 watches now, going back and forth tweaking tires day and night squinting at the gauge to see which side of the tick mark from perfect they are. I've reverted to my former mode of tire maintenance, set it and forget it unless something actually happens that requires intervention. The TPMS is handy for verifying you didn't have a leak overnight and to warn of serious over or under pressure but for the most part I ignore the numbers. I set them all before a trip and unless something fails they will be fine for a few weeks at least. I put in an extra 10lbs or so when I winterize, come springtime I bleed down when cold to operating pressure and that usually carries me through half the summer. Back when I rode my scooter I'd tweak up and down a couple PSI to balance stiffness and contact area for going through twisties but a 90PSI tire on a delivery truck has no such performance subtleties.

Mark B.
Albuquerque, NM
 
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