Air pressure in tag axle tires

[ebprod]

I just had my coach weighed at a Cat Scale. The motor home is a 1994 Newmar Kountry Aire with a tag axle. The tires are LT235/85R 16E.

These were the weights I got:

Steer axle- 5920 lbs
Drive axle- 12580 lbs
Gross weight- 18500 lbs

I have a tag axle and a GVWR of 20,000. Since I wasn't given a separate weight for the tag axle, how would I figure the air pressure in the tires? They are Michelin XPS Ribs.

-Joe

[LVJ58]

Hi Joe, looks as if you have the Ford f53 chassis. I would refer to the Michelin load inflation table for your size tires, then based on your axle weight, I would inflate them accordingly. As for the tag wheel tires I would inflate them the same as the duals.

We also have a tag axle on our 22,000 GVWR coach with Bridgestone load range "G" 245/70R19.5 tires. I inflate all my tires to 80psi which is the minimum psi shown for "G" rated tires on Bridgestone's load inflation table.

Good luck & safe travels,

[ebprod]

It is a F53 chassis, with 16" wheels. Since I didn't get a separate weight for the tag axle, can I take the total weight of the drive axle and divide by six to get the weight for each tire?

If I do that and use the weight of the tire times two, I get a weight for the duals as 4193 lbs. The charts says to use air pressure of 55 psi. Does that sound about right? Should I put that in the tag tires as well?

-Joe

Quote:

Originally Posted by LVJ58 Hi Joe, looks as if you have the Ford f53 chassis. I would refer to the Michelin load inflation table for your size tires, then based on your axle weight, I would inflate them accordingly. As for the tag wheel tires I would inflate them the same as the duals. We also have a tag axle on our 22,000 GVWR coach with Bridgestone load range "G" 245/70R19.5 tires. I inflate all my tires to 80psi which is the minimum psi shown for "G" rated tires on Bridgestone's load inflation table. Good luck & safe travels,

[justimagination]

.........80 lbs in all tires, your good to go, that's what I use with great ride, tire wear, no sway. Good luck and travel safe.
David G.

[Lt46]

Agree with the above and it says the same on my door panel tire inflation label. 80 psi for dualies and tag. Haven't had a problem doing it this way.

[LVJ58]

Joe, here's Michelin's load inflation chart--it will give you an idea of what pressure you need in your tires for the axle weights you have:

Michelin Americas Truck Tires XPS RIB® Page

Based on their chart, it would appear you could safely run 55 or 60 psi in all tires.

A single tire your size at 55psi will carry 4110lbs so x2=8220lbs--your front axle weight is only 5920lbs. In dual configuration at 55psi one set of duals will carry 7446lbs x2=14892lbs and your drive axle weight is only 12580lbs, so at 55psi you would be OK. To keep it simple, I would run 60psi in all 6 tires, but that's your choice.

I wouldn't run 80psi in your 16" tires, 80 is OK in 19.5 tires and larger. Also most rims have a pressure limit stamped inside them.

Good luck, Jim

[ebprod]

Hi Jim,

I think you are mis-reading the chart. The chart provide in your link is the weight per axle, not tire. It is confusing because I have a different Michelin chart that goes per tire.

Based on your chart, I should have 80psi in the front axle. It is the rear axle I can't figure out because I have the combined weight for both rear axles.

-Joe

Quote:

Originally Posted by LVJ58 Joe, here's Michelin's load inflation chart--it will give you an idea of what pressure you need in your tires for the axle weights you have: Michelin Americas Truck Tires XPS RIB® Page Based on their chart, it would appear you could safely run 55 or 60 psi in all tires. A single tire your size at 55psi will carry 4110lbs so x2=8220lbs--your front axle weight is only 5920lbs. In dual configuration at 55psi one set of duals will carry 7446lbs x2=14892lbs and your drive axle weight is only 12580lbs, so at 55psi you would be OK. To keep it simple, I would run 60psi in all 6 tires, but that's your choice. I wouldn't run 80psi in your 16" tires, 80 is OK in 19.5 tires and larger. Also most rims have a pressure limit stamped inside them. Good luck, Jim

[LVJ58]

Quote:

Originally Posted by ebprod Hi Jim, I think you are mis-reading the chart. The chart provide in your link is the weight per axle, not tire. It is confusing because I have a different Michelin chart that goes per tire. Based on your chart, I should have 80psi in the front axle. It is the rear axle I can't figure out because I have the combined weight for both rear axles. -Joe

I very well could be mis-reading the chart joe. It might be best if you called and spoke with a Michelin Tire Technician and give him your axle weights & tire size and get their recommendation for a safe tire pressure to carry your load.

When I had a question on the minimum pressure I could use in the Bridgestone tires on our coach, I called one of their techs and was advised 80psi was the minimum for load range "G" tires of my size.

Better to be safe than sorry,

Good luck & let us know what you find out,

Jim

[Nick-B]

Hi Joe,

Your tag axle will be carrying considerable less weight than the drive axle.

I did a full weigh on my F53 w/tag chassis last year and while I don't have the numbers with me right now, the tag was light enough that I could have only run 40 PSI in the tires according to the charts. I ended up putting in 50 (in the tag tires).

If you can't get a separate weight on the tag, then you'll just have to "best guess". Most folks recommend a little more pressure than less as an underinflated tire will run hot.

[ga traveler]

Look on the wall right by the drivers seat. You will find your chassis data plate. It has the tire press. on it.

[ebprod]

I am putting the full 80psi in the front tires, since that axle is close to max. The rears I am putting 65psi. That is higher that the chart show, but I wasn't fully loaded when I got it weighed.

We are taking it out this weekend so we'll see how it handles.

-Joe

Quote:

Originally Posted by Nick-B Hi Joe, Your tag axle will be carrying considerable less weight than the drive axle. I did a full weigh on my F53 w/tag chassis last year and while I don't have the numbers with me right now, the tag was light enough that I could have only run 40 PSI in the tires according to the charts. I ended up putting in 50 (in the tag tires). If you can't get a separate weight on the tag, then you'll just have to "best guess". Most folks recommend a little more pressure than less as an underinflated tire will run hot.

[Nick-B]

Hi Joe,

I finally remembered to look at my weight charts and our coaches are pretty close to the same. I have a bit less on the front and more on the rear.

My axle weights:
Front: 5420
Rear: 9320
Tag: 3580
Rear+Tag: 12900

I am a bit heavier on the Left side due to the big slide on that side so you probably are too, but not enough to run different pressure side-to-side.

65psi in your rear duals is probably about minimun with no margin for additional load. I'm running 70psi but I do have more rear weight. 65 in the tag is OK but 50 should be plenty. For my coach, that is what the chassis data plate says to run on the tag tires.

Have a good Easter weekend.