Born Free Leap'n Lions RV Club Info & Discussion Forum

We have a 2016 Splendor (27' rear side bath effectively) on an F550 chassis. Ford recommends a cold front tire pressure of 95 psi and a rear tire pressure of 110 psi. BF recommends 70 psi. We found that a pressure of 70 psi at about 45°F will cause the low tire pressure alarm to go off when the temperature falls below freezing (something that still happens from time to time in Wisconsin). Ford's pressures trigger the high pressure alarm. (BF sets the alarms to about 67 psi and 95 psi). We use a cold pressure of about 73 psi and that seems to have worked well. We just had an oil change and multi-point inspection and the Ford dealer inflated the tires to the factory recommendations. The ride home did indeed seem stiffer than what I'm used to.

What pressure do you use for your tires?

An example of the guidelines I use--

http://www.michelinrvtires.com/assets/p ... ion-rv.pdf

The only way to determine the proper inflation pressure for RV tires is to use the inflation guide published by the tire manufacturer and to know the weight at each tire position when the RV is loaded as you usually travel. My F-550 came with Continental tires and I obtained the inflation guide for commercial vehicle tires from their web site. Born Free provided me with the empty vehicle weights at each tire position when I took delivery. Since then I have weighed the RV at a commercial truck scale which gave me the loaded weights on each axle. By using the two weights I can reasonably estimate the loaded weights on each wheel.

Your weights will be different but on mine, the front axle weighs about 5,340 lb. and the rear axle about 11,540 lb. The tire size is 225/70R19.5 G and the chart indicates 75 psi for the front tires (up to 3040 lb. on each tire) and 80 psi for the rear duals (up to 3000 lb. on each tire). I round these up a bit to allow for temperature and load changes and use 85 psi all around.

I had forgotten how well Continental hid their tire inflation tables for their 19.5" truck tires until I had to find it again recently.

For those who are still searching, it is at:
http://www.continental-truck.com/truck/ ... loadcenter

The DOT requires that all brands of a given size of tire have the same inflation recommendations. Therefore the tire inflation tables for Continental's 19.5" truck tires will also apply to other brands of the same tire size.

I have long suspected that all the charts were the same but never bothered to compare them and had not heard that it is a legal requirement.

I just compared the Continental and Michelin charts for 225/70R19.5 G tires and see that the information is presented differently. For an unbalanced load, the Michelin guide could lead to one tire (or set of duals) being under inflated. The Continental guide lists the pressure depending on the weight at each tire whereas the Michelin guide lists the pressure depending on the weight of the entire axle. As I recall, previous Michelin guides I used showed weight on each tire but since I don't have any of the old guides available, I am not entirely sure of that.

The guidance I have always used is that proper inflation is determined by knowing the weight at each tire position and setting the pressure for all tires on each axle based on the tire or duals that support the most weight. If there is very little side-to-side weight difference then either approach yields a safe pressure. However, some motor homes have differences exceeding 500 lb. from side to side and in that case it seems the Michelin approach could result in under inflation.

My guess is that tire company legal departments have a considerable amount of influence in how the inflation charts are presented and for those of us driving Born Free RVs, any chart for the proper size and load range is adequate. A slightly over inflated tire will run cooler and is probably safer than one that is slightly under inflated.

From the above linked Michelin pdf:

The loads indicated represent the total weight of an axle end, in an RV application. When one axle end weighs more than the other, use the heaviest of the two end weights to determine the unique tire pressure for all tires on the axle.

[quote="montir"]The only way to determine the proper inflation pressure for RV tires is to use the inflation guide published by the tire manufacturer and to know the weight at each tire position when the RV is loaded as you usually travel. My F-550 came with Continental tires and I obtained the inflation guide for commercial vehicle tires from their web site. Born Free provided me with the empty vehicle weights at each tire position when I took delivery. Since then I have weighed the RV at a commercial truck scale which gave me the loaded weights on each axle. By using the two weights I can reasonably estimate the loaded weights on each wheel.

Your weights will be different but on mine, the front axle weighs about 5,340 lb. and the rear axle about 11,540 lb. The tire size is 225/70R19.5 G and the chart indicates 75 psi for the front tires (up to 3040 lb. on each tire) and 80 psi for the rear duals (up to 3000 lb. on each tire). I round these up a bit to allow for temperature and load changes and use 85 psi all around.[/quote]

I am using the same numbers with my 27" 550 Triumph having followed the same logic withe same tires.

So I just weighed my RV and the front axle total was 3740 and the rear axle total was 9450. Which means (making the assumption of each side is equal - the local scale wasn't wide enough to test each side) the front half is 1870 and the back is 4725. Our tire size is 225 / 75R16. From looking at the chart we should have about 48 psi on the front and 76 in the back. That seems way too low for the front axle doesn't it? Am I reading something wrong on the chart?

John,
Nope. In my view a lot of folks carry too much pressure in front and not enough in rear. It is a good idea to weigh each wheel though.
Ralph

Yeah, tried to weigh each one, but there was a concrete abutment on each side of the scale so I couldn't pull it off to the side of the scale. Good to know about the pressure though, just seemed really low to me. The way to do it makes perfect sense though. (believe it or not, that's how I set the pressure on my bike tires - but with a bathroom scale instead!)

[quote="BikerJohn"]So I just weighed my RV and the front axle total was 3740 and the rear axle total was 9450. Which means (making the assumption of each side is equal - the local scale wasn't wide enough to test each side) the front half is 1870 and the back is 4725. Our tire size is 225 / 75R16. From looking at the chart we should have about 48 psi on the front and 76 in the back. That seems way too low for the front axle doesn't it? Am I reading something wrong on the chart?[/quote]

I believe your max pressure for those tires if E rated is 80 psi. And assuming there are 4 rear tires, that would mean an approximate load of 1180 per tire. If the max load of each tire (from the sidewall) is (say) 1750 lbs, then in theory you are operating at about 67% of capacity and should have a MINIMUM inflation of 67% of 80 psi or 53 psi. I have been told but can find no basis, that it's unwise to inflate less than 75% of capacity which is 60 psi to which you should add 1 psi for every 2 deg the cold ambient exceeds 68 deg when you check inflation. Your results may vary depending on the Load Index rating of your tires which varies the maximum load at max pressure but that number will be molded on the tire sidewall. This is the theory which I had the misfortune of learning post the Michelin LTX tire failure recall from their technicians. None of this applies to ST trailer tires that are so badly constructed that there is little meaning or value in the tire ratings, again in my unfortunate experience(s).

Hey folks,

I also had a question on tire pressure for our 2003 24RB.

The BF manual reads "FT 60 PSI and Rear 65 PSI"

But the Fuel door has a picture that reads "65 PSI for the front and 80 PSI for the Rear".

Also, on the inside door of the driver side there is sticker from Born Free (Dodgen Industries INC.) that reads "65 PSI front and 80 PSI Rear".

Thoughts?
GVWR = 14050 LB
GAWR - Front = 4600 LB
GAWR - Rear = 9450 LB

Should I go with the Manual at 60 and 65 PSI or go with the stickers = FT 65 and Rear 80?

--Kevin

As the earlier posts suggest, go have your coach weighed both front axle and rear axle in down the road traveling condition. Then inflate your front and rear tires per the attached inflation chart for the best results. This graph is for LT225/75R16E tires which should be the tires on your coach.

I believe the correct model name of admoffat's coach on a F550 chassis is "Royal Splendor" and the tire size is 19.5". Born Free coaches on the E series Ford chassis have 16" tires. The best advice in this thread is to have the coach weighed. It is best to have each wheel weighed individually and adjust tire pressure per the mfg's charts. The reason for individual tire weighing is that one side of a coach might be heavier than the other and it would be enough to put you at a higher pressure for the entire axle. Hard to find folks to do such weightings check out this url to get a schedule of one organization where this can be done properly https://rvsafety.com This group is an excellent source of information on RV weights and tire pressure.