Tire Pressure

[mr.ken]

Since Im new to class A, I was wondering what pressures you guys are running. On my TH I used to run close to the max depending on how it was loaded. I am taking my first trip tomorrow, no Toad, and I want to check and adjust the pressure.......Do I need to go as high as the max???? How much will it affect the ride, or not at all????

[tmmar]

The higher the pressure, the more you will feel the road (expansion joints, bumps, etc). I run my tires at 95psi. Weight of coach is about 27000lbs.

[mr.ken]

Thanks. the man. sticker says 90 psi is max..........can I go a little lower than that for a smoother ride when I have a light load???

[cfsoistman]

Originally Posted by mr.ken

Thanks. the man. sticker says 90 psi is max..........can I go a little lower than that for a smoother ride when I have a light load???

I stick to the 90 lbs as written on the sticker. It feels fine to me at that pressure. Just remember you're on a Truck Chassis so it's not going to be like a limo ride. Smooth roads, it's great, rough roads, it bangs and makes quite a bit of noise. It doesn't drive like an air suspension type chassis. I added air springs to help with the rocking from passing trucks and it really helped.
Enjoy your trip! I'm heading out tomorrow for York PA and the Train Collectors semi-annual Train Meet.

[tmmar]

cfsoistman,
have a great trip!!

[cfsoistman]

Originally Posted by tmmar

cfsoistman,
have a great trip!!

Thanks so much. The weather looks a little iffy but any day camping and looking at trains beats the pants off working!

[ronhanson]

The tires should be inflated to the tire manufacturers recommendations.
They rate the pressures based on your actual weight so you'll need to visit a truck scale loaded how you normally would be while traveling. If you have the Michelin XRVs 90psi is too much and really more than the chassis can handle anyway for weights.

Michelin Tire inflation guide is online here.
Make sure you click the right wheel size and find your tire in the chart. I'm sure Goodyear has something similar.
They really want a 4 corner weigh so you can see how much is on each tire and use the maximum, but I haven't found a scale that will do that yet.

I've attached one of my scale receipts from when we did a heavily packed 10day trip. As you can see, I was pretty heavy. I was within 380lbs of my GCWR since my car is so heavy, YIKES! An empty 357QS is 680lbs heavier than my 350TS, and a 378TS is 460lbs heavier so your weights may be similar if you're half the pack rat I am.

I had 6780lbs on my front axle which is 3390lbs/tire. The chart says I could run them at 70psi but since I don't know the exact tire weight I run 75-80 and maintain some safety margin.

I had 14280lbs on my rear axle which is 7140lbs/dual. Chart says to run them between 80-85. I run them at 85.

My toad is the last weight on the receipt.

I had many complaints about the ride and handling of my chassis before getting the tire pressures correct. It's better enough now I have little thoughts about any other chassis upgrades. Running the right pressures insures will get you the most life out of your tires and give you the best ride.

[kvtaylor]

We run ours at the Georgetown motor home recommended pressure of 90 lbs all the way around. Always check the tires in the morning when its cool and the sun has not started to warm the tire up. That can cause an error in the tire pressure. It will increase with the sun shinning on them over a period of time.

[NWJeeper]

Ron, thanks for the numbers. I haven't had ours weighed yet but I'm thinking we are fairly close to your numbers. I need to find a convenient scale to get to.

Setting the pressure to your actual weight is the preferred method so that we aren't making the ride harsher than it has to be while still being safe.

[mr.ken]

Thanks. Before my bigvtrip in June I will have it weighed and use that Michelin chart

[TulsaSteve]

The other numbers to look at are the chassis specs. I run 85 in the front and 90 in the rear. The front of my 2007 F53 is spec'd to handle 7,500 lbs out of the 22,000 GVWR.

https://www.fleet.ford.com/truckbbas...essd_07mhc.pdf

The XRV tire chart pegs 85psi at 3950 per tire, so I'm actually over by 400 lbs.

90 psi in the front would put me over by ~700 lbs and for me that's overinflated.

90 psi in the back (given dualies) gives me 15,060 lbs. The chassis is set up to put 14,500 of the 22,000 in the rear.

So in the rear I'm over by 560.

So I could weigh it all the time and putter around with the pressure to get it just right, but I assume that the weight isn't even and so I leave them over a little bit and don't worry about it. I would rather be a little over than under.