Double check my tire inflation numbers please :-)

[akeyzoo]

Ok, have had tires inflated per the sticker inside, 120psi front and 95psi rear duals.

Finally did a 4 corner weigh.

LF. 5620. RF. 5660
LR. 9920. RR. 9900


Seems I am overinflated. What should my Michelin XZA2 295/80 22.5 inflation be.

https://www.michelinb2b.com/wps/b2bc...s_Brochure.pdf

Just want someone to dbl check me before I recallibrate my tpms and all.

Thanks chris

[BFlinn181]

I calculate
80 lbs front
80 lbs rear duals.

The numbers on the sticker are often the maximums, not adjusted for weight.

[Steve Ownby]

Chris,

I would probably go 85-90 all the way around. The numbers on the table is the minimum pressure required to carry that weight. There is no issue with going a little higher pressure while under inflation is dangerous and destructive.


Steve Ownby
Full time since '07

[Crasher]

If you run 5 psi over the minimum at a 60* morning temp, you will have an acceptable morning cold starting pressure for almost any temp from 30 up to 80* and most altitude changes. I do that and I can travel from WI to AZ via Colorado and Utah with all the temp and altitude changes and the cold morning start pressures are always above the minimum and below the max.

[ImagineIF]

I never run my tires at the minimum required and would never run them at Michelin's lowest rated tire pressure. I will sacrifice ride for safety. I run my pressures 10-15 psi over minimum and can't feel the difference in ride.

Use a calibrated pressure gauge and go with 95 psi on the steer and 90 psi on the drive assuming your weights were fully loaded. Your front weight is the max at 80psi, so even another front seat passenger pushes you over 80psi. You might be surprised how far off some gauges can be.

BTW, at your weights I'm surprised you don't have 275s. Have your tires been upgraded. Does the manufacturer's decal show dry weights and loaded weights?

[akeyzoo]

Thanks guys.

Ya, these are original tire sizes. I do have unloaded, loaded and max weight on stickers. Just surprised how much below capacity I am on steer axle, rear axle about maxed out.

I am on a trip and will wait to adjust steer axle pressure until I am home. Last time I tried to adjust a schrader valve stuck open.

Chris

[SeeTheUSA]

The largely-accepted formula from an experienced tire person on the Tiffin Network forum is to add 5% to the scale weight, then add 5psi to what the chart says. Provides a bit of a safety factor rather than to risk under-inflation.

[Fred Cooper]

Originally Posted by BFlinn181

I calculate
80 lbs front
80 lbs rear duals.

The numbers on the sticker are often the maximums, not adjusted for weight.

I agree. If it were my coach, I'd be running 85 front and rear assuming that the weights were full tanks and loaded for travel.

Fred

[Ray,IN]

Keep in mind the RMA states over 90% of ALL tire failures are the result of underinflation/overloading. What is a good way to reduce your odds of a tire failure_ never risk running them underinflated/overloaded. The mfgrs recommendation for tire pressure will account for driving a max'd out coach weight.

[Shadow0120]

I would say 85 all the way around.

[BFlinn181]

I hope all this 'fine tuning' of tire pressure recommendation is taking into account some other important factors. Tires can lose 1-4 psi each month due to air molecules traveling through the rubber of the tire. (Thin walled bicycle tires can lose 5 psi a day!) Tires never GAIN air, only lose it. Also, on a 70º day, a rolling tire can increase pressure due to heat by 10-15 psi. The recommended numbers by tire manufacturers is the minimum psi to safely carry the maximum load. Most (over 75%) tire failure is due to under inflation. Under inflated tires wear faster (on the outside edges) and reduce fuel mileage.