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Old 07-16-2016, 08:04 AM   #15
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Originally Posted by Waiter21 View Post
DTW et al;

An argument for the higher inflation pressure ??

I suspect that the temperature inside the tire is related directly to how much the tire is flexing from the road contact and the sidewalls. The rubber flexing generates a lot of heat.

A higher inflation pressure would result in less flexing and less heat..

Although lower inflation pressure may improve the ride, After seeing the temperatures from the TPMS, I'm rethinking my cold inflation pressure. I currently run 70 psi in all 6 MH tires based on weight and the tire table, I may take my tires back to 100 psi.

I think on my next long trip, I'll start it out at my 70 psi and take careful note on handling and ride quality for a day or two, then bump them up to 100 psi and see if I can detect any difference in ride and handling.
I assume you have 22.5 tires and seen the following equation.

(Axle Weight from weight scale) divide that by 2 then multiple that by 1.05 to allow for 10% variance. Then look that up on the tire chart then add 5 psi for margin of safety. Do this for each axle since the result is typically a different psi front versus rear.

Also there is the recommendation to use a minimum of 75% of max inflation. I doubt that it will apply in your case, but in general, after you use the above equation and then you add 5 psi for margin of safety, if that is less than 75% of the max inflation, then inflate to 75% of max inflation. Dont add safety margin of 5 psi in this situation.

If you have run 22.5 tires on a Class A at 70 psi for any length of time, you have damaged them and have unsafe tires.
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Old 07-16-2016, 03:14 PM   #16
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I have 19.5 inch tires (225/70R19.5) .

Based on real weights (5,100 front, 7,800 rear)

Looking at the manufacture table, I should run a minimum of 70 psi in all six tires.
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Old 07-16-2016, 03:59 PM   #17
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Temps do affect tire pressure, but they the are accounted for in the specs. This is why they tell you to set the pressure on cold tires because they know the pressure will increase as they heat. Follow the tire and MH guidelines.

I had mine set to 95 PSI cold and after driving for a few hours I checked them and they were 125 PSI. The temp on the blacktop was over 120F.

All the people I talked to that deal with the nuances of large tires like big rig drivers and servicers have always told me that an over inflated tire is much safer than an under inflated one and when a sound tire has a blowout it is because of under inflating, not overinflation. Since I don't have anyone more credible to defer to I tend to keep my tires 100% full.

I always keep mine at the recommended PSI or slightly higher. Never had a bad ride from harder tires. I do notice if my tires are a little lower they are more prone to dragging me around the round in the grooves in such.
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Old 07-16-2016, 04:32 PM   #18
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Quote:
Originally Posted by Waiter21 View Post
I have 19.5 inch tires (225/70R19.5) .

Based on real weights (5,100 front, 7,800 rear)

Looking at the manufacture table, I should run a minimum of 70 psi in all six tires.
Glad to hear that. When a 22.5 tire is at 70 psi the side wall bulge is very
pronounced. Retired F-4 driver and you ?
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Old 07-16-2016, 05:29 PM   #19
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Originally Posted by Vsilvester View Post
Has anyone used a heat gun to check tire temperatures at different pressures
I have a Newmar 4301 Mtn Aire i had it weighed they told me to run 110 lbs in frount and 90 in rears including tag
The truck shop says i should run 120 all the tires i think the ride is kinda rough .
What do all you suggest ?

Can i check tire temp to see whats happening any ideas on what the normal temps should be ? I have a heat gun .

Thanks for all the anticipated feedback




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I have....for more than 30 years. I have a RayTec MT-4 non-contact infra red thermometer. Temperatures should be uniform across the tread and from tire to tire. Temps vary depending on ambient and road surface temps. But, as a group should be mostly the same with some variation between individuals. You need to keep a log for awhile to get perspective on what's normal operating temp because it varies day-to-day and hour by hour.

I use the TP recommended on the placard @ the driver's door for guidance. No higher as that's for MAX GROSS WEIGHT. Since I'm 700-1000 lbs less....a PSI, two or three less.

Occassionally, the LF or LR duals may be ~ 10F higher than their mates due to the camber of the road. Next time you check it....they will be back to the usual temps.

What I look for is a tire with an unusually hight temperature or non uniform temps across the tread. The latter likely indicates that the tire is under (high edge temps) or over (high temps in the center) inflated.

Thinking on this.....it might be better to measure in Celsius. That would give you less variation between readings and make life easier. One degree C = 1.8 degrees F.

It's low tech & old school. It also forces you to actually LOOK at the tire's condition....usually several times a day.
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Old 07-16-2016, 06:05 PM   #20
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Originally Posted by gateaux01 View Post
If you have an accurate weight of your axles. Look up your specific tires load inflation tables. Inflate according to it

I personally would not get a heat gun near my tires. I really think you would have zero chance getting any useful information from doing so
Many people misunderstand load/inflation charts. They are there to show the absolute minimum air pressure to support the corresponding load; not the optimum pressure.
You'll not find one tire manufacturer that recommends running less air pressure than what the vehicle mfgr. recommends on their tire placard.
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Old 07-22-2016, 06:56 PM   #21
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A timely thread for me as I was wondering the same question for our tires. I found inside the coach a label that says 100 psi all around. When i was cleaning the wheels I saw engraved on them 120 psi. So am I reading the mfgr recommends 100 for a softer ride and the wheels for safer tire life?
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Old 07-23-2016, 02:48 AM   #22
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Originally Posted by McKTX View Post
A timely thread for me as I was wondering the same question for our tires. I found inside the coach a label that says 100 psi all around. When i was cleaning the wheels I saw engraved on them 120 psi. So am I reading the mfgr recommends 100 for a softer ride and the wheels for safer tire life?

If I'm reading your question correctly, short answer yes, lower pressure softer ride.

But there are many variables that can effect your personal experiences.

I think most have already been mentioned so no use beating a dead horse.

For you, and your 100-120 PSI range, a little experimentation will get you what you are looking for in the handling, ride quality, and tire performance department.

DTW
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Old 07-23-2016, 05:41 PM   #23
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A timely thread for me as I was wondering the same question for our tires. I found inside the coach a label that says 100 psi all around. When i was cleaning the wheels I saw engraved on them 120 psi. So am I reading the mfgr recommends 100 for a softer ride and the wheels for safer tire life?
No, the 120psi rating on the rims is the maximum "cold" air pressure rating for the rim, has nothing to do with the tire. For instance you buy tires with a theoretical sidewall pressure rating of 200psi; 120psi is the maximum pressure you can safely run in those tires because of rim limit.

The vehicle mfgr. recommendation on the tire placard is what their design engineers determine is the optimum safe air pressure for that particular vehicle. Once is a while the design engineers determination is ignored; remember the Ford Explorer roll-overs? That was due to insufficient air pressure in favor of a softer, more comfortable ride.
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Old 07-23-2016, 08:30 PM   #24
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I have my fronts at 105psi and the drive and tag at 95psi. The temp sensors on my TPMS rarely get over 135 degrees.
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Old 07-23-2016, 08:45 PM   #25
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Good information to know Ray, thank you. I did look at the sidewalls of the tires and it says max 120psi. Sooooo, don't want to run at to low a pressure. 100 psi is 83% of maxiumum psi is that safe for the tires? Seems like a pretty significant difference to me who does not know much about this. I know on my car I keep the tires at the max because they are supposed to wear better.
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Old 07-24-2016, 06:12 AM   #26
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Mxktx,
Weigh your axles and use a tire manufactures inflation chart for cold pressure.
I add +5psi for a safety cushion.
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Old 07-24-2016, 09:28 AM   #27
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Good information to know Ray, thank you. I did look at the sidewalls of the tires and it says max 120psi. Sooooo, don't want to run at to low a pressure. 100 psi is 83% of maxiumum psi is that safe for the tires? Seems like a pretty significant difference to me who does not know much about this. I know on my car I keep the tires at the max because they are supposed to wear better.
I always run what the vehicle mfgr. recommends on their tireplacard. This is what they recommend for that vehicle from unloaded to fully loaded conditions.
Running less pressure does not significantly improve ride comfort, which is the main reason some MH owners run less pressure, it does however increase tire heating from more sidewall flex. Heat is the main cause of tire failure, which originates from underinflation/overloading.
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