Tire Inflation Charts

Question

Yesterday on the way home, I stopped at the scales. In round numbers, the front weighed 3,800 lbs. and the rear (dual) was 6,900 lbs. I was able to get both axles on the scale, so the front and rear did add up. The recommended pressure for the RV is 62 PSI front and rear. When I replaced the original Continental Vanco tires with Michelin LTX MS/2, I started out at 64 PSI and that seemed to be OK. Lately, I have tried a bit more pressure and I can feel that is too much. When I consult the inflation chart from Michelin, the recommended pressure for the actual measured weight on the axles is 50 PSI. I assume that is the minimum recommendation. The door sticker on the RV says 62 PSI, so roughly that is about 4,500 lbs. front and 8,300 lbs. rear. I will say that at the Winnebago recommended pressure, it does steer better and does better with cross winds and sharing close quarters with big trucks. I'd like to compare notes with others on their experiences with adjusting pressures up or down. Also; did switching tire types or brands cause you to experiment with tire pressures?

pianotuna · Answer

Hi,I was over weight on the driver's side dual and so replaced all the rims and when to a taller tire that had more load capacity. I run at the door panel pressures (80 and 65), but the ride in the E-450 is rough

off_pavement · Answer

When I switched to Yokohama tires on our E450 Sunseeker 2300, I had to deflate the tires significantly from the door sticker. After perusing tire pressure charts (Yokohama doesn't have one for my tire that I can find) based on my loaded weight, I'm now over-pressure at 50 psi in front and 65 in the rear. The charts call for 45 front and 60 rear for my loaded weight.

I have very limited experience with this tire pressure other than our recent 4000 mile trip towing our Jeep Wrangler. Passing trucks and cross winds have a greatly reduced effect. Grooves, dips, and truck wear in the lanes don't throw the RV around anymore, and unless I see unusual wear, I plan on sticking with this pressure.

YMMV!

desert_captain · Answer

The door stickers in any motor home are close to useless. They are merely recommendations based upon what your rig "might" actually weigh. Replace the original tires and your door sticker becomes less than useless.

The only way to correctly fill your tires is to load (realistically), and go to the local Cat Scale. Take those actual readings and check that particular tire manufacturer's load/inflation tables and air up accordingly. The same size tire from different manufacturers can vary greatly in actual load capability not to mention how it rides and handles.

:C

j-d · Answer

It'd help to know which tire size you're running. If they're the LT225/75R16(E) that the Michelin chart suggests, then your weights call for 50-PSI front and rear just as you said. If your coach was loaded as you expect it to be loaded, on actual trips, then 50 is what the pressures should be. And, from the chart, 50 is not the lowest they allow for inflation pressure. You should be fine if your weight is based on the proper loading.
And to know what you're driving, too. Year, Make, Model. I can only repeat, EMPHATICALLY, that overpressure in front tires, especially on a Ford, is bad news for handling.

EDIT: Oh, forgot. Tires are standardized. That means that if the size and load range are an exact match to one manufacturer's chart (like Michelin), it can be used for another brand (like BFG or Hankook). A Michelin may outlast another brand or ride better, but the inflations should be the same.

golden_hvac · Answer

Hi,Because you did not get side to side weights, consider this.  One side of your RV might be say 300 pounds more than the other side.  You could have a significant difference in front tire load weights.  This is especially true for RV's with a slide out on the drivers side, front, they can typically be at the max tire weight rating on that one tire, while others are less than the max weight.So I would keep running 65 PSI front, and can go down a bit on the rear tires, just making sure that they will not rub against each other in the back.  Check the lower portion while on pavement, see how much space is left back there.RUnning the max tire pressure of 80 PSI will cause it to ride like a lumber wagon, so deflating a small amount can cause the tires to absorb much more vibration, instead of transmitting it to the frame and passengers!Good luck,Fred.

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