tire pressure

You definitely need to get four corner weighing done in order to accurately set your tire pressure. Side to side weight differences can be significant, well over 1,000 pounds. If you weigh at a Cat scale and split the measurement you could be in for trouble if your rig is not balanced.

Go with the RV manufactures recommendations for tire inflation until you get four corner weights.

Here's a web site with more information for your reading pleasure: RV Weigh - Mobile Weigh Station

ClassAGeek wrote:
With all due respect to those who are trying to help, I wish people would do some more research before adding their comments.

The manufacturer's PSI numbers print inside your MH are MAXIMUM values. They are pressures required for a fully loaded coach using the OEM tires. Use different tires or (hopefully) drive at less than 100% loading or tow a toad and you can use lower PSI.
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x2 - the values on the sticker in my MH were much higher than the tire manufacturers guide once I got it weighed. Rode like it was on rocks until I weighed it and set psi correctly. Don't go by the stickers unless you have no other choice. Weigh it and check with the tire manufacturer.

With all due respect to those who are trying to help, I wish people would do some more research before adding their comments.

The manufacturer's PSI numbers print inside your MH are MAXIMUM values. They are pressures required for a fully loaded coach using the OEM tires. Use different tires or (hopefully) drive at less than 100% loading or tow a toad and you can use lower PSI.

LOWER PSI = SMooTHER RIDE.

I have a F-53 spring loaded chassis, so using the minimum safe tire pressure is essential for a smooth ride.

Weight carrying capacity follows a relatively gentle performance curve near the low end of the scale. Being 1 psi over doesn't make you instantly safe, and 1 psi under is not suddenly dangerous. Many factors go into the weight rating. Know them and you will be safer than most.

Factor #1: Weight carrying capacity is speed related. Capacity increases greatly as you slow down. If a given tire can carry 8000 lb at 60 mph it will carry more than 16000 lbs at 20 mph and 32000 lbs at 10 mph.

Factor #2: Cold tire pressure ratings are given because tire manufacturers (and their lawyers) are worried that you might misuse the data ON THE HIGH end. Blow outs are far more common due to overinflation when the tire heats up and exceeds the rim / tire limits. Unlike the low end of the range, the Weight Carrying Capacity drops suddenly at the high limit.

Factor #3: Tires do not care if they are cold or hot. As I hop you have notice, a tire feels cushy at 80 psi cold or hot. It feels harsh at 100 psi cold or hot.

How do I keep the lowest safe pressure? After measuring my coach on a CAT scale, I find 76 psi is correct for my rear tires and 80 psi is correct for the front according to tables provided by Michelin. (BTW: I ignore the insignificant differences between right and left. When moving, the distribution tends to equalize - so just pick the heavier side). Now here's my secret: I set my COLD pressure to 74 psi rear and 77 psi front and yet I am 100% safe. How is that?

I drive at less than 40 mph until my tires warm up and my TPMS shows that pressure has increased to my normal driving range of about 80 psi rear and 84 psi front which is well into the safe range specified by Michelin for 70 mph. It never takes more than 10 minutes - and I have the smoothest riding gasser you will ever drive.

Maybe I can make this Michelin chart will post where you can read it. First in reading your post I knew the rears would not need more psi than the front based on your weights so I looked up the chart. I come up with 85 front and 75 rear with enough cushion to not add 5 more psi.
Chart is for axle weights and yours are: 10840 F and 18340 R

275/80R22.5 H
PSI..... 75.... 80....... 85..... 90..... 95...... 100.... 105.... 110.... 115
S... 10140 10620 11100 11680 12190 12700 13220 13580 13940
D... 19480 20280 21040 22040 22700 23360 24020 24820 25640

You should weigh all four corners, then consult the Michelin inflation chart to find the correct pressure.

I had to experiment with tire pressures to find out what worked for me. I run Michelin XRV on all of my coaches and Michelin & Winnebago both recommended 75 lbs. PSI rear and 90 lbs. PSI for the steer tires. I do not like to run tire pressures on the low side due to lower tire inflation contributes to higher heat build up. Plus I was getting tire squirm from the rear tires. I ran different tire pressures every time I went out RVing and I found I got the best handling at 100 lbs. PSI all around. And that tire pressure works for my RV also due to long tread and tire wear I got 10 years out of my last set of Michelins. Good Luck on whatever tire pressure you choose.

PastorCharlie wrote:
My inflation rates per Newmar table are 100 psi each 255/80/22.5 tire, front and rear. Check in the driver's area for manufacturer chart listing inflation rates.

check the mfg chart carefully and i'll bet you see that the 100-psi recommendation is based on the RV being at the GVWR. you aren't wrong inflating to 100-psi. heck, I had a roadside service call a few years back for a blowout and the service guy told me he just inflates all of his truck tires to the max cold inflation and doesn't worry about the weight. as I said, you're not wrong but unless your RV weighs in at the GVWR i'll bet you could soften your ride by reducing the tire pressure and maybe get better handling. both Winnebago motorhomes that we've bought new recommended using a tire pressure based on an assumed weight of GVWR.

wolfe10 wrote:
Rich,

I agree, but it is really the MINIMUM PSI for a given weight. If it weighs any more, you move right on the chart to the next higher PSI.

We may be talking semantics here, as both agree on the plus 5-10 PSI.

yes...when i wrote "for the load being carried" I meant exactly what you wrote..."for a given weight". semantics. :)

Rich,

I agree, but it is really the MINIMUM PSI for a given weight. If it weighs any more, you move right on the chart to the next higher PSI.

We may be talking semantics here, as both agree on the plus 5-10 PSI.

wolfe10 wrote:
Remember, the chart gives the MINIMUM PSI for a given weight.

If these are not individual wheel position weights, add 5 PSI to account for side to side imbalance.

I always add a 5 PSI "safety reserve" to the minimum.

So, 5-10 PSI over the minimum.

the Michelin chart gives the minimum PSI for the load being carried. I agree with the 5-10 psi over minimum.

we have the same tires as the OP except ours are load range 'G'. we took delivery yesterday and just determined my wet weights (full fuel, water and LP tanks...nothing else on board) today. front axle weighs 7,140, rear weighs 15,100 making 3570 per tire in front and 3775 per tire in the rear. at those weights the Michelin table calls for 70-psi all around. once the MH is fully loaded as we usually travel I will re-weigh and set inflation accordingly likely rounding up to the next highest inflation for unequal corner weights.

the placard on the driver's door of our MH indicates a cold pressure of 100-psi front and rear but that is based on an assumed GVW of 9000-lbs front and 17,500-lbs rear and not the actual weight of the motorhome.