[George]

I would suggest weighing each axle so the tire pressure can be set for your coach. With that said, I’m sure you have yours too high. It looks like you have a 40′ Coach so it weighs less than mine, and my recommended pressures are 105 front, duals 95 and tag 75.

[Jon]

Yes it’s a XL40 not much weigh on it other than

the 12 kw Powertech generator. Thanks for the

info! I was thinking the pressure was to high.

I use to run the old tires @ 90 on the rear and it

never was bumpy. It was very smooth.

Thanks Eric

[Mike]

Absolutely weigh your coach loaded. My 92 XL40 was set at 110/110/110 when I bought it and several members helped me weigh and use the Michelin RV tables. Including a 5psi safety margin, my tires are 105/95/90.

[Chuck & Katrina]

I also use 5lbs up from the Michelin chart and my 40 footer is 110/95/95

---

2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[Mike]

I want to Thank you all and let you know how

valuable you are! After checking tires on drive and tag axle.

I found 3 @ 110 psi and 3 @ 120 psi.
no wonder it bounced like a basketball.
Leaving out of Atlanta Friday back to LA

(Lower Alabama). I will post the results

Thanks again for the expert advice!

[Jon]

Mike T. When we bought our 1992 XL in 2009 with 8.25 wide alloys wheels and its original 12R’s tires, we upgraded to 315’s. Thats when we discovered Michelin had two different pressure charts. One for 12Rs on 8.25 wheels and one for 315/80/22.5 mounted on 8.25 inch wide wheels. Since the 315 is leaning towards being a bit pinched on the narrower wheel, Michelin has a slightly lower psi on chart for weight carried. In our case, made for a softer smoother ride.

[Dick]

Jim,

Glad you point this out, “12Rs on 8.25 wheels and one for 315/80/22.5 mounted on 8.25 inch wide wheels”.

R

[Jon]

Jim, Thanks for the information! I adjusted

the air pressure to 95 psi. Still bumpy in the

rear tires over 65 mph. I must confess these

tires are not Michelin’s. I’m thinking now that

they need something to balance them or I’ve

got some bushings that are bad back there.

All comments appreciated! Thanks

[Jim/Chris]

Not saying this is your issues, just some info to consider.

I have worked with a few customers in the past that all said they had a bumpy ride at 65mph. One of them even spent a week at Prevost. They adjusted air pressures, checked alignment, replaced ball joints etc. All of them turned out to be a tire balance issue.

So if all else fails, might have a look at that.

[Jon]

Mr. Taylor,

Weigh your bus with full fuel, water. Adjust tire pressure according to Mechelin tire charts and most important install a set of Centramatics all around on your bu

Several Prevost converters install them on their new deliveries.

All 3 of my Marathons had Centramatics on every axles.

Centramatic is a long time advertiser on PC with many positive postings. Go to their web site too watch videos

Al

[Jon]

Without trying to go crazy with minutia, a lot of balance issues are in fact not balance but tires installed on the wheels improperly. The best way to start is verify you have no runout, something that must be done with a dial type micrometer that can measure the tire runout while it is being rotated.

A quick, easy cheap preliminary check is to look at the tire where the bead is seated on the wheel. There is a tiny raised bead that goes around the tire at the wheel and it should be equidistant around the entire perimeter between the wheel and tire.

A tire mounted to a wheel vertically instead of laying horizontal can cause this problem and while balancing will correct it short term it will get worse and unti or unless the tire is trued up through shaving the tire will never run smooth.

[Jon]

Jon is referring to this ring;

[Archived]

Thanks Al.

To add to my comments above, If there is runout but the tire is showing equal spacing around the bead Al shows it can also be attributed to how the wheel is mounted on the coach. Put the greatest amount of runout at the top by rotating the tire. Loosen all the lug nuts to allow the wheel to drop a miniscule amount and retighten the nuts to spec.

Remeasure runout and it is likely much less than previous.

A high quality tire shop will always mount and seat the bead on tires when they are horizontal, often with the wheel sitting on a pail or 5 gallon bucket. That allows the tire to seat evenly. A good shop will also consider runout because balancing will only mask temporarily the problem. There is a whole lot more to tires than that they are black, round and hold air.

[Deleted User]

I read the previous articles about tire run out.

After inspection the bead is equal all the way

around the rim. I’ve got to check the run out as

Jon suggested next. Hopefully I will get this

solved soon it’s driving up the wall. Thanks

[DON]

Where can I buy the balance rings and what

do I need? Thanks