Which Air Pressure is Correct?

[golden]

I've never paid a great deal of attention to it, but there is a discrepancy in how much air I should put in the tires of my MH. The plaque on the door and on my owner's manual specifies 90 psi front and 85 psi for the rears. However, on the Workhorse My Motorhome website, it specifies that I should use 100 on the fronts and 90 on the rears. Anyone have any idea why the discrepancy and what the "real" answer should be? I normally am at 21,500 lbs fully loaded (GVWR is 22,000 lbs) and just barely under all the prescribed weights for front and real axles. The weight is distributed as per instructions from Michelin (I have Michelin 235/80 22.5 tires). Incidentally, both the plaques I mentioned are put there by Winnebago.

[The General]

Hey Golden,

Winnebago suggests a smoother, less bumpy ride @ 90/85.
I personally like to have a bit better fuel economy with 100/90.
In the end, it's your preference to which you will adhere to.


Steve Bernard

[UFO Pilot]

I believe the majority of folks on this site would give you the following advise:

1. Weigh your RV, preferably all 4 corners, but at least front and rear.

2. Use the tire manufactures tables to determine the proper air pressure.

3. Add 5 pounds to the recommended pressure.

Someone will surely correct me if I am wrong.

[ccook129]

Quote:

Originally Posted by wthomas1 I believe the majority of folks on this site would give you the following advise: 1. Weigh your RV, preferably all 4 corners, but at least front and rear. 2. Use the tire manufactures tables to determine the proper air pressure. 3. Add 5 pounds to the recommended pressure. Someone will surely correct me if I am wrong.

Ditto

[Alan_Hepburn]

Quote:

Originally Posted by wthomas1 Someone will surely correct me if I am wrong.

This is the internet - someone will correct you whether you are right OR wrong!!!

[UFO Pilot]

Quote:

Originally Posted by Alan_Hepburn This is the internet - someone will correct you whether you are right OR wrong!!!

I started to say that and thought better.

[The General]

Let's all consider ourselves corrected

Steve

[kennersonf]

I use the method Wayne mentioned. I put 85 psi in the front and 90 psi in the rear. These pressures are for maximun axel ratings of 8000 lb front axel and 14,500 rear axel. I am lighter than 8000 lbs on the front but still use the max axel rating. My rear axel is always near max when fully loaded.

[DriVer]

Quote:

Originally Posted by kennersonf I use the method Wayne mentioned. I put 85 psi in the front and 90 psi in the rear. These pressures are for maximun axel ratings of 8000 lb front axel and 14,500 rear axel. I am lighter than 8000 lbs on the front but still use the max axel rating. My rear axel is always near max when fully loaded.

My strategy allows me to set my air pressures to my GAWRs. I have an 8500 GAWRF and a 15000 GAWRR, I run 95F and 90R. The inflation presssures that I use include a +5 psi margin.

[Photog]

Hi Denny,

You and I have essentially the same coach and most likely run at the same weights.

The good folks at Redlands weighted my four corners. The front axle was at 7,200 the rear at 14,200 overall 21,400 (close to yours). Based on those weights they came up with the recommended pressure from the Michelin RV tire guide of front 90 psi. and rear 85 psi.

That said I put in an extra 5 lbs and run the front at 95 psi and the rear at 90 psi.

I hope this helps.

Bill

[golden]

Quote:

Originally Posted by Photog Hi Denny, You and I have essentially the same coach and most likely run at the same weights. The good folks at Redlands weighted my four corners. The front axle was at 7,200 the rear at 14,200 overall 21,400 (close to yours). Based on those weights they came up with the recommended pressure from the Michelin RV tire guide of front 90 psi. and rear 85 psi. That said I put in an extra 5 lbs and run the front at 95 psi and the rear at 90 psi. I hope this helps. Bill

Do you have any idea why there is a difference between what Michelin and Workhorse recommend for the air pressure? You would think they would be the same.

[Photog]

Quote:

Originally Posted by golden Do you have any idea why there is a difference between what Michelin and Workhorse recommend for the air pressure? You would think they would be the same.

I have know idea, except that maybe Workhorse took a one size fits all approach.
This subject gets a lot of press.

[DriVer]

Quote:

Originally Posted by golden Do you have any idea why there is a difference between what Michelin and Workhorse recommend for the air pressure? You would think they would be the same.

I believe that WCC may be recommending inflation pressures equal to the GAWRs of the chassis and Michelin is making their recommendations based on weights and loading that would apply to their tires on any vehicle. That would probably be in the ballpark.

[frankdamp]

Do it per the weight on the axle for your worst-case loading and use the tire manufacturer's data. Not 5 or 10 psi over, that's over-inflation and doesn't give you a "safety margin".

It's like saying that at 5' 9" you should weigh 180 lb, but you'll eat until you're 185 to give you a "safety margin".