What Tire Pressure?

[JVR]

My previous post 12/15:
Go to michelin's site enter your tire and weight per tire, dividing the axle by 2 of course and it provides the correct air pressure. Mine is 120 front and 105 rear and tag.
and 007's post 12/14:
I would follow millerj's advise for now than after you have your coach fully loaded get it weigh and follow the tire pressure tables for tires you have and weights you get loaded with your stuff not some one else's.
They can be found in QT's 1 & 2.

[Tireman9]

Comment 1 Shame on your dealer. They should have ensured all the tires were inflated to the Placard inflation.

Comment 2 Shame on your dealer for not spending time to be sure you understood proper tire inflation and correct vehicle loading and how to get the unit weighed. This is not surprising. Few dealers seem to want to let owners know the vehicle weight and tire inflation as the ride might not be as good as the buyer might want so the dealer might loose a sale.


You can learn more than you probably want to know about tires and proper inflation at my blog.

[montiem]

I have a tag axle and have been told by my tire man to run 100 all around, I was talking to an MH guy said he runs 100 in front, 95 in dual and 85 in tag. I have looked on the Michelin site and I cannot figure out who is right and as far as that goes what Michelin is saying.

[Steve Ownby]

Originally Posted by montiem

I have a tag axle and have been told by my tire man to run 100 all around, I was talking to an MH guy said he runs 100 in front, 95 in dual and 85 in tag. I have looked on the Michelin site and I cannot figure out who is right and as far as that goes what Michelin is saying.

You really need to have your coach weighed. Corner weight is best but axle weight is ok. What size are your tires? Without axle weights you should inflate tires to support the GAWR. Your coach has the following GAWRs. 1. Steer axle. 16000 pounds 2. Drive axle. 20000 pounds 3. Tag axle. 10000 pounds With your tire sizes go to the Michelin inflation table and find your inflation pressure.

Tire selection and tire pressure tables.

[Tireman9]

Originally Posted by montiem

I have a tag axle and have been told by my tire man to run 100 all around, I was talking to an MH guy said he runs 100 in front, 95 in dual and 85 in tag. I have looked on the Michelin site and I cannot figure out who is right and as far as that goes what Michelin is saying.

1. You should have a tire placard or spec sheet posted on the wall of your RV MH. It shows the suggested inflation based on what the manufacturer thinks you will be carrying.

2. With your RV fully loaded with the fuel, food, clothes, people, toys and even your bowling ball collection if you normally carry that around :-) get on a truck scale to learn what your axle weights actually are.

3 Assume you have some imbalance so calculate that one side of each axle is loaded to 55% of the total. (This is just an estimate and you need to try and get individual loads calculated to be sure) WORKSHEET HERE.

3. (A) Instructions for Goodyear Tires.

3. (B) TIRE SIZE CALCULATOR

4. The "Dual" loads shown on Mich charts are for the two tires. You can confirm this by reading the sidewall of your tires.

Example for READING MICHELIN CHART on a 255/80R22.5 XRV LR-G tire
Lets assume your Front axle gave you 8910# so 55% of that is 4900.5 and rounding up we would want the minimum inflation needed to carry 4901#. According to MI chart that would be 4975 which gives 100psi as your minimum cold tire inflation. Add your 5 psi margin and you know you need to set the fronts at 105 psi.

--------- MICHELIN SIDEWALL CRACK PHOTO's as tires age.

Moving to your rear duals. With a scale reading of 15,010# we would find 55% of that or 8255.5 or 8256# for the TWO tires on the heavier side of the RV. Looking at the MI chart we find 8410 as the load number which indicates 90psi add the 5 psi margin and we have 95psi.

Tag axle Assume you have the axle loading set so the scale reads 7560#. 55% of that is 4158 and looking at the chart we see 80psi. Adding the 5psi margin you now know you need 85psi cold in the tag tires.

Remember ALL tires on each axle should have the same cold inflation. COLD inflation means not having been driven on more than 2 miles in the previous two hours and not being in any sunlight in the last two hours.

Hope this helps

[montiem]

The weights on my on my placard inside the coach Front 16000/ 125#, duals 20000/85#and tag 10000/75#. In addition it has these weights 7248/125, duals 9060/85 and tag/75. I realize the pressures are for the actual weights or the second set of numbers or the gross vehicle weight not loaded, right. Or is the weights for the axle weights or the first numbers. Sorry if this does not make sense.

[montiem]

Sorry tire size 315-80. 22.5

[montiem]

Thanks Tireman I have read the articles you suggested and I have a lot more information than I can can understand in one night. I do have a few questions, my front axles are 16000, I assume that max weight is 8000/ axle and from weight table if I had the max weight on the front axles the correct tire pressure for a 315/85 22.5 would be 115#, the rear with 20000 max would be 85, I think that is right. How do you figure thr tag, 10000#max axle weight! or 5000# each end would be 85. The question I have about the tag! at 5000# each the tire pressure would be 85# I think. I am assuming max weight on all axles.

The tire placard says 125 front, 85 rear duals and 75 for tag.

[Tireman9]

Here is the corrected link

http://fifthwheelst.com/documents/Br...eWeighForm.pdf