coach weight and tire pressure

[R F S]

Had my 05 Mandalay weighed at a truck scale and the readings were shown like this... Steering 12200
trailer 19200
-----------
31400 lbs.

I am thinking this is front and rear lbs.. Is this a reasonable method to use to inflate tires? Currently at 100psi for 2 front and 4 rear.
Thanks for any input RFS

[Sky_Boss]

It is a start but you really need corner weights to complete the picture.

Do you have any more info to share such as your axle weight ratings and tire maker/size?

[Gary RVRoamer]

Yes that is a reasonable place to start. Individual tire weights would be better, but what you have is adequate.

Divide the front (steer) axle weight by two to get individual tire weight and then add 300-400 lbs to allow for a possible imbalance (one side heavier than the other). Then look that up in the inflation table for your brand and size of tire to get the recommended psi value. Maybe go 5 lbs higher to give some extra safety margin.

For the rear (drive) axle, divide by 4 to find individual tire weights and add 300 lbs each for possible imbalanced load. Then look that weight up in the inflation tables. Again, an extra 5 psi will help assure you won't ever be low.

[Ray,IN]

Keep in mind all the weight/inflation charts say that is the minimum recommended pressure for the corresponding load. It is not necessarily the optimum pressure.

[adonh]

Originally Posted by Gary RVRoamer

Yes that is a reasonable place to start. Individual tire weights would be better, but what you have is adequate.

Divide the front (steer) axle weight by two to get individual tire weight and then add 300-400 lbs to allow for a possible imbalance (one side heavier than the other). Then look that up in the inflation table for your brand and size of tire to get the recommended psi value. Maybe go 5 lbs higher to give some extra safety margin.

For the rear (drive) axle, divide by 4 to find individual tire weights and add 300 lbs each for possible imbalanced load. Then look that weight up in the inflation tables. Again, an extra 5 psi will help assure you won't ever be low.

On the Michelin inflation guide for the tires on my coach they list tire pressure by weight as Single and Dual. I put together a chart based on the GVWR per chassis ID tag, the actual scale weight of the front and rear axle (unable to weigh the 4 corners), a mid range weight between GVWR and actual weight and finally the tire maximum pressure per Michelin. I then matched up as close as I could the PSI per the chart.

275-70R 22.5 tire inflation guide.pdf

Based on this what would be the recommended tire pressure, front and rear, thanks

[FlyingDiver]

Originally Posted by Ray,IN

Keep in mind all the weight/inflation charts say that is the minimum recommended pressure for the corresponding load. It is not necessarily the optimum pressure.

Never seen that verbiage on the Michelin charts. They say:

For RV use only, Michelin displays tire loads per axle end in the load and inflation tables, as we recommend weighing each axle end separately and using the heaviest end weight to determine the axle's cold inflation tire pressure. For control of your RV,it is critical the tire pressures are the same across an axle, while NEVER exceeding the maximum air pressure limit stamped on the wheels.

Emphasis mine.

[Gary RVRoamer]

On the Michelin inflation guide for the tires on my coach they list tire pressure by weight as Single and Dual. I put together a chart based on the GVWR per chassis ID tag, the actual scale weight of the front and rear axle (unable to weigh the 4 corners), a mid range weight between GVWR and actual weight and finally the tire maximum pressure per Michelin. I then matched up as close as I could the PSI per the chart.

Since you don't have a scaled weight for the coach when loaded for travel, you have to assume the axles may be fully loaded to their GAWR's. That means you would use the line you have labeled "GVWR".

You could gamble on the "midway" numbers, but they are only 5 psi different than the GVWR set, so there is really nothing to be gained by taking that chance.

[2 Stroker]

I just had my coach weighted at the FMCA Rally in Albany,Or (4 corner wt) and I'm over wt in the rear by 1150lbs and under in the front by 730lbs. In January I got a new set of Michelin 295/80R22.5 XZA2 with a max PSI of 120lbs.
With a combined wt of 33,620lbs
FR 6,405lbs-FL 6,065lbs RR 10,195lbs-LR 10,955lbs
I have to run 105 PSI in the front and 100 PSI in the rear by the numbers given. This is the only way to get a true wt reading and know what PSI to run, money well spent. Must be the new steel and copper radiator and not the way the wife packed the coach on the LR
2 stroker

[Sky_Boss]

Originally Posted by 2 Stroker

I just had my coach weighted at the FMCA Rally in Albany,Or (4 corner wt) and I'm over wt in the rear by 1150lbs and under in the front by 730lbs. In January I got a new set of Michelin 295/80R22.5 XZA2 with a max PSI of 120lbs.
With a combined wt of 33,620lbs
FR 6,405lbs-FL 6,065lbs RR 10,195lbs-LR 10,955lbs
I have to run 105 PSI in the front and 100 PSI in the rear by the numbers given. This is the only way to get a true wt reading and know what PSI to run, money well spent. Must be the new steel and copper radiator and not the way the wife packed the coach on the LR
2 stroker

I'm Confused...

You were 1150# over on the rear?! That is a lot. There is no way that I know of to simply use more tire pressure to compensate for that. You still have to deal with the axle rating no matter whether or not your tires can handle the weight.

Maybe I missed something?

[2 Stroker]

Originally Posted by Sky_Boss

I'm Confused...

You were 1150# over on the rear?! That is a lot. There is no way that I know of to simply use more tire pressure to compensate for that. You still have to deal with the axle rating no matter whether or not your tires can handle the weight.

Maybe I missed something?

The numbers are with a full tank fuel and full water but I only run with 20-25 gallons of water because we stay at campgrounds all the time. He said if I could move some of the stuff to the front bay that would help but he said Country Coaches are just heavy. Overall I am 420lbs over but if I take off for about 80 gallons of water I should be 220lbs under. The numbers say 100psi rear and 105psi front. There is nothing I can do about it beside taking the bed out, I may just do that and go with a sleep number because the one in there must weigh a good 200lbs
2 stroker

[dons2346]

Rear axles on most coaches are rated at 23,000lbs. It is DOT that says each axle cannot be over 20,000.

1150 over on the rear isn't bad at all considering that the non tag Beaver and Safari with the big Cat motor was overweight out of the factory before you put your toothbrush in it. There was a model of the Travel Supreme that was in the same situation. I know of a TS single axle that was taken back to the factory where they cut it apart and installed a tag.

Floyd, what does your data plate say? Most CC's say 120 front and 110 rear.

Also might help if you unload some of that ammo you carry and don't blame the extra weight on the wife!

[2 Stroker]

Originally Posted by dons2346

Rear axles on most coaches are rated at 23,000lbs. It is DOT that says each axle cannot be over 20,000.

1150 over on the rear isn't bad at all considering that the non tag Beaver and Safari with the big Cat motor was overweight out of the factory before you put your toothbrush in it. There was a model of the Travel Supreme that was in the same situation. I know of a TS single axle that was taken back to the factory where they cut it apart and installed a tag.

Floyd, what does your data plate say? Most CC's say 120 front and 110 rear.

Also might help if you unload some of that ammo you carry and don't blame the extra weight on the wife!

Don
The front reads 105psi
rear 95psi
She said, what jn the world can you put in these things. We have boxes in the garage that came out of the Alpenlite 5er. I did unload the ammo but she wants it back in so my toothbrush will stay home.
2 stroker

[Mr_D]

Originally Posted by dons2346

Rear axles on most coaches are rated at 23,000lbs. It is DOT that says each axle cannot be over 20,000.

Nope, the DOT added an exemption for RV's now and they are allowed to use 23,000# axles. This was over a year ago. And very few MH's had 23,000# axles before this. The old Monaco tried this and ended up having to buy back some single axle units and replace them with tag axle units.

[Mr_D]

Originally Posted by 2 Stroker

In January I got a new set of Michelin 295/80R22.5 XZA2 with a max PSI of 120lbs.

On Michelin tires and some others the pressure on the tire sidewall is the minimum to support the maximum rating of the tire. This is spelled out in their literature.

From page 2 of the 06/07 Michelin RV Tire Guide: "If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."