I finally bought new tires.

Single tire rated at 3970 at 110 lbs

Dual tire rated at 3750 at 110 lbs.

I took the rv to a certified scale.
The fuel tank and propane were both full
Both passengers and both dogs were in their places..
No food, No water, and no clothes were in rv.
So possibly 500 lbs more on each axle.

The Barth weighs 5320 on steer axle.
8500 on drive axle.
13820 gross weight.

What would be the correct pressure for this weight?

Front
3970x2=7940 tire capacity
5320+500=5820 steer weight
7940x.74=5875
.74x110= 82.5 lbs

Back
3750x4=15000
8500+500=9000 drive weight
.6x15000=9000
.6x110= 66 lb

The math shows 82.5 lbs in front and
66 lbs in the rear.

I think I would rather 85 lbs in front and 80 lbs on the rear. What do you think? Is my math right?

Well lets see,....they say that the biggest cause of blow outs is underinflation. Also it is one of the causes of poor mileage due to increased rolling resistance. So no matter what the math says, to me a tire with a 110 lb. max being run at 66 lbs. is half flat. I wouldn't run any less than 90 lbs. But hey! they are your tires and you are the one paying for them!!!

Dusty, what your data tag read for gvaw on you axles, Our P-30 chassie is 5000 front, 9850 rear, 14500 gvw. 70lb tire presure. I run 75+ in mine. At 95 psi the ride is a lot harsher. I think you will be ok in the 80-85 range.
Doorman

I have never found a data tag on the command center. I have the duals at 80 lbs and the steer aT 90 lbs. I too dont want to run a tire half flat..

Find out what the tire maker recommends.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

http://www.michelinrvtires.com...inflation-tables.jsp

This is a generic tire chart.
It does show 65 lb would carry the rv.
Think I'll try 75 Lbs in all of them and see how it rides. Thanks.

quote:

Originally posted by dustyjeeper:
http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

http://www.michelinrvtires.com...inflation-tables.jsp

This is a generic tire chart.
It does show 65 lb would carry the rv.
Think I'll try 75 Lbs in all of them and see how it rides. Thanks.

Be sure the manufacturer does not have a minimum pressure. I have that situation on the front, due to high LR oversize tires.

Keep in mind that those figures are the minimum pressure that you can run at that weight, and like Bill says, the tire may have a minimum safe pressure that may be higher than that. Another thing,.....ever hear of anybody weighing their car and basing their tire pressure on that??? I never have!!! Most people run their tires at close to max air pressure unless they are an offroader or duner. If running a tire that is 35 lbs. max 20% low is considered flat, (28 lbs.) Than running a 105 tire at 20% would be at 84 lbs.....so running it at 66 lbs. would be getting close to 40%. So even though that math says you could run at 66 lbs. for the weight you have, do you really want to do that?

quote:

Originally posted by Shadow man:
.ever hear of anybody weighing their car and basing their tire pressure on that??? I never have!!!

Neither have most tire technicians.

quote:

Most people run their tires at close to max air pressure unless they are an offroader or duner.

I dunno.........I think most people keep the stock size and follow the factory sticker on the car.

I add ten psi to the manufacturer's chart on our Barth

As far as my cars go, I use the mfgers recommened pressure on the door post and never more than 2 pounds over that. In fact radials will act like you are driving on ice if to overinflated.

On our Barth I use the tire pressure from the tire companies websites.