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cgreer00 03-10-2017 07:21 PM

Understanding my tire pressures
 
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Hey everyone,
I am trying to make sure that my tire pressures are safe to drive on for our first trip until I can get to a facility where I can weigh my coach. There isn't one nearby and I don't want to drive 100 miles, roundtrip, just to weigh my coach before our first camping trip in the motorhome.

Please let me know if I am doing this correct and share any information you might have:

Coach: 2002 Monaco gasser, 37 feet, 2 slides. My wife, myself, and two small children. We don't have much packed because this is our first trip, and there is currently NO water in our holding tank or black tanks.

GVWR (22000), GAWRfront (8000), GAWRRear (14500)

Tires are new Michelin XRV 235/80 R22.5, no tag axle.

According to this chart my tires should be inflated to 85 lbs in the front and 85 in the rear if the coach is fully loaded to the Gross Axle Weight Rating. There is no way we are loaded that much, because if we were then I would never be able to carry water or lots of food, or when my kids get older and are heavier we wouldn't be able to have them with us. Now, I won't have exact values until I weigh the coach on all 4 corners, but can't I make a reasonable assumption that I can safely drive this coach an hour away to the state park with my tires inflated to 80-85 lbs in the front and rear?

Does this sound right? Am I missing something?

Thank you!

(I've attached the Michelin chart for my size tires below)

BFlinn181 03-10-2017 07:53 PM

What does the sticker next to the driver's seat suggest? The sticker is usually the pressures for a totally loaded RV. If you adjust perhaps 10 psi below the recommended sticker pressures you'd be safe.

Typically the dual tires are lower than the front, since you're spreading the weight on 4 tires instead of 2. 85 psi sounds high for the rear tires.

By the way, according to this public truck scale locator, there are two scales 22 miles from Athens, GA.

CAT Scales

Truck scales near Athens

cgreer00 03-10-2017 08:02 PM

Thank you! Didn't know about that resource but I will bookmark it. The sticker on the coach says 95 lbs front and 85 rear, but of course that was back in 2002 so I don't know if anything has changed in regards to tire technology.

BFlinn181 03-10-2017 08:43 PM

Quote:

Originally Posted by cgreer00 (Post 3495264)
Thank you! Didn't know about that resource but I will bookmark it. The sticker on the coach says 95 lbs front and 85 rear, but of course that was back in 2002 so I don't know if anything has changed in regards to tire technology.

Probably the sticker wasn't for Michelins, but I don't think the pressures would be that much different. Since engine is in front, 85 PSI in front is probably O.K. for your first trip or two. In the rear, I'd go with 75-80 PSI since the weight is on 4 tires and you say you're traveling with no liquids in your tanks.

Gary RVRoamer 03-10-2017 08:53 PM

Quote:

The sticker on the coach says 95 lbs front and 85 rear, but of course that was back in 2002 so I don't know if anything has changed in regards to tire technology.
The "technology" of air pressure hasn't changed in the last several millions years, so not to worry. As long as the current tires are the same size as shown on the placard by the driver seat, you are safe using those recommended pressures. They are intended to support a fully loaded coach, i.e. the coach weight is equal to the GVWR. When you get it weighed you may find you can use less psi and get a softer ride, but the higher amount is still valid.

If the current tire is of a different size, use the axle GAWR values to estimate the tire load and look that number up in the inflation tables. Take the front axle GAWR and divide by 2 (2 tires) and then add about 10% in case one side is heavier than the other. Same process on the rear axle, except divide the rear GAWR by 4 (4 tires).

cgreer00 03-11-2017 06:15 AM

Thanks a lot, much appreciated.


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