Determining Optimal Cold Tire Pressure

[RVerOnTheMove]

So I got my RV weighed this past Friday, Front Axle: 3670 (wife and I onboard in the cab) and Rear Axle: 8160.

An axle weight of 3670 does not mean that you have a left tire weight of 1835 and a right tire weight of 1835. It's quite possible that it could be 2035 and 1635. That's the reason that 4 wheel weighing is highly recommended as you would have to inflate both tires to the level required to carry the one heavy tire. It would also be a good indication that you need to take a look at what is stored where and see if you could shift heavier items to a different location.

[tireman9]

So I got my RV weighed this past Friday, Front Axle: 3670 (wife and I onboard in the cab) and Rear Axle: 8160.

So as I understand I would use 1835 as the load weight for the front and 2040 as the load weight for each tire on the rear (duals).

Now when I go to the charts, Goodyear and Firestone both are the same.

For the front I have either 1790 or 1940 listed on the Single line. Which should I start with?

For the rear I have either 1995 or 2150 listed on the Dual line. Which should I start with?

Then whichever I go with I know I should take that pressure and add 5 lbs. Does that sound right?

You might want to follow the logic in my post on Tire Pressure. i.e. add 5% to tire load to accomodate the probable unbalance, Consult the tables and do the math then add 10% to avoid daily pressure changes as you travel.

Remember the Goodyear & Bridgestone Firestone charts show individual tire loads not axle as in Michelin tables.

Basically all tire companies and regulatory agencies worldwide follow publishes industry standards with only minimal deviations on some individual tires by some companies. If your tire company doesn't offer its own tables showing some exception then a reasonable approach would be to follow the major tire companies.

If your load at inflation molded in the tires match the numbers in a table then you can be pretty confident the rest of the values will follow. I have never seen an instance where the maximums match but the lower published values do not match.

I also strongly suggest you get a TPMS as even checking the tire pressure every morning does not mean you did not pick up a nail as you drove out of the campground.

[gypsies2]

First I would get the RV weighed. The front axle, rear axle, the whole RV weight.

Second, I would get each tire weighed so you definitely know what each axle each side weighs for the exact tire pressure. If you have dual wheels in the back, take your total weight on each side and divide it in half since you have 2 axles or 2 tires on one side each. I hope I didn't confuse you, but if you get it weighed, the people will show you. I think this is a must for you, since most RV's are overloaded, and I confirmed this at a good Sam Rally I just attended and also talking with people over the last 30 years of doing this.

John

[HMillsJr]

What about running the psi marked on the side of the tire?

If load is less, should that pressure be reduced? When I got my coach it had 80lbs, side wall says 125. Which do I use?

I can understand the confusion.

[RVerOnTheMove]

What about running the psi marked on the side of the tire?

If load is less, should that pressure be reduced? When I got my coach it had 80lbs, side wall says 125. Which do I use?

I can understand the confusion.

You really can't do anything until you have your RV weighed. You need to get a tire weight for each individual tire (or pair) and then go to the tire manufacturers website to see what the proper inflation level is. In most cases it will not be be sidewall pressure but it could be. If you use a professional weighing service such as RVSEF, they will give you the proper inflation specs for your vehicle.

[wolfe10]

Agree with Bill-- you need to get the RV weighed so you can determine the correct PSI.

Until then, look at the GVWR plaque which is normally in the driver's area. It (by law) will give recommended tire pressures ASSUMING each axle is loaded to its GAWR. Not really accurate, but a reasonable starting point.

Brett