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Old 06-03-2020, 08:47 AM   #1
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Tire psi over chart values

What would the consequences be of running tires over the psi chart values but not over the max pressure on the tire? Is there a problem with running tires at the max tire pressure and the coach being at a lesser weight than Max?
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Old 06-03-2020, 08:49 AM   #2
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Great question. Other than a rough ride what's the harm running the max?
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Old 06-03-2020, 08:52 AM   #3
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Almost all commercial trucks run nameplate vales to make the tires last longer

How often do you see truckers letting air out of their tires after delivering a load? perhaps never/
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Old 06-03-2020, 09:06 AM   #4
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I always run with the max cold PSI stated on the tire. I am more worried about a sagging tire wall than a rougher ride.
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Old 06-03-2020, 09:07 AM   #5
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I always run with the max cold PSI stated on the tire. I am more worried about a sagging tire wall than a rougher ride.
That's more or less what I do. My max is 120 and I try to run 110.
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Old 06-03-2020, 09:10 AM   #6
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Hello STExxx,

I run mine about 5 psi above the RV manufacturers rating, it results in a slightly better gas mileage, however, more wear in the center of the tires, less contact when wet, a bit of a harsher ride etc. etc..

The more pressure you use, the more the negative aspects will be.

I increase my pressure a bit if I can not dump and have full tanks, better be safe than sorry. Plus the dually tires need more pressure in order to carry more weight especially if you loose one.

Never run your tires when inflated to the maximum rating. Once you start driving, the air will heat up and the pressure increase, obviously going beyond the maximum pressure rating, asking for a blowout to happen.

Cheers!
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Old 06-03-2020, 09:13 AM   #7
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Hello STExxx,



I run mine about 5 psi above the RV manufacturers rating, it results in a slightly better gas mileage, however, more wear in the center of the tires, less contact when wet, a bit of a harsher ride etc. etc..



The more pressure you use, the more the negative aspects will be.



I increase my pressure a bit if I can not dump and have full tanks, better be safe than sorry. Plus the dually tires need more pressure in order to carry more weight especially if you loose one.



Never run your tires when inflated to the maximum rating. Once you start driving, the air will heat up and the pressure increase, obviously going beyond the maximum pressure rating, asking for a blowout to happen.



Cheers!
My understanding is that there suggested pressures are for cold tires. The manufacturer has already accounted for heat increasing the pressures somewhat.
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Old 06-03-2020, 09:18 AM   #8
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If the inflation is LOT more than the value in the tables, the center of the tire tread will wear before the rest of it. That's a long term consideration and may not be significant enough to wear the tire out before old age or a road hazard gets it first. Excessive psi on the front wheels will also result in "squirrel-like" steering, where the front seems to wander and constant correction is needed. A lot extra may be enough to notice some rougher ride as well.


How much is "a LOT"? I'd say around 20%, which would be about 16-20 psi on a typical class A. The value in the tables is actually the minimum for the load, so you should always stay above it. Smart owners usually run 5-10 psi high just to be sure it never goes lower than the minimum.
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Old 06-03-2020, 09:21 AM   #9
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Nothing wrong, if there was they wouldn't lable for that pressure.

For some who think that the tire is going to wear more in the middle at max inflation, ( not above it ) here is a picture of a tire profile.

The inside is round but the tread is flat, with belts to keep it that way.

https://www.bridgestoneamericas.com/...e-constructionClick image for larger version

Name:	08-Component_TireConstruction.jpeg
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Old 06-03-2020, 09:23 AM   #10
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I agree that the Max cold rating takes into consideration that the tire will exceed that level when under load and at varying speeds. I also have a Max cold rating of 120 and run between 110 & 115.


As a backup I do have my tire monitoring system set to alarm me if the tire temperature exceeds 140 degrees.
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Old 06-03-2020, 09:31 AM   #11
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Thanks, my feelings is like most, no real harm, maybe quicker tread wear but not a big problem for part timers as age will determine change. I hear you about rough rides given some of today's interstates. Rough ride could possibly be harder on fastened parts on the coach and chassis. All advise taken and appreciated, Thanks
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Old 06-03-2020, 09:36 AM   #12
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Originally Posted by rffowler55 View Post
I agree that the Max cold rating takes into consideration that the tire will exceed that level when under load and at varying speeds. I also have a Max cold rating of 120 and run between 110 & 115.


As a backup I do have my tire monitoring system set to alarm me if the tire temperature exceeds 140 degrees.

Yep!! That's pretty much exactly what I do. My max is 120 (cold) and I run about 110 (cold), my warm/hot pressure may reach 120-125 but that's expected. I don't recall what the maximum temperature is set to for my TPS, but I do know I set one somewhere around 140ish.



SIDE NOTE: I had an aftermarket TPS system trigger an alarm on my pickup truck when I had a brake caliper hang and the wheel temperature got too high. Probably saved me a lot of grief by warning me early.
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Old 06-03-2020, 09:58 AM   #13
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That's more or less what I do. My max is 120 and I try to run 110.
Exactly what I do on all three axles

Placard actually was at 110 on all three

After loading up fo a year that actually came close to the charts which were close to 100 all around

I do try to load the back heavier which worked

No soft squishy tires for me or hot sidewalls
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Old 06-03-2020, 10:07 AM   #14
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Get the coach weighed at each wheel position, then set your cold inflation pressure to the tire manufacturers chart for the heaviest wheel position on each axle (+10% if you want a margin of safety).
For my coach, that's nowhere near the max cold inflation PSI, but that will vary based on weight of coach and the tires installed.
As stated above, any higher and you're likely to see excess wear in the center of the tread.
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