tires

[dreamin533]

Hi to all. I know this topic has been posted and beat to death a few times, but I am not able to find specifics in the threads. I own a 2008 Berkshire 360QS with the mercedes diesel engine. I am not able to find any information in changing tire sizes. The coach has 255/80R22.5 (limited manufacturers) and the GVWR according to freightliner is 29,410 lbs. That is 19,000 on the rear and 10,410 on the front. I have read in a couple of threads that a Freightliner oasis dealer can upgrade the front air bags to accommodate 275 series tires and increase the front GAWR to 11,000 or 12,000 lbs. Freightliner has denied this in emails I have sent to customer service and their only response is to check with a tire dealer. MY issue is the recommended tire pressure to be at the 80-85% mark of GVWR is 105 to 110 psi. it makes for a bit of rough ride, especially in the front. The other thing I have come across is the 255/80 are 14 ply tires where most of the 275's are 16-18 ply. If I could go to the 275 size tires, from what I have read I would need 90 to 95 psi in the tires therefore softening the ride. Any thoughts or real world experience and possibly a contact at freightliner that won't blow me off would be appreciated. Thanks, Roy

[Phil57]

Roy your 08 can be modified to take the 275/80 tires. I'm not sure where you are but have the FL dealer call the service center at Gaffney. They have done a bunch of them and can give the dealer an idea where to get the info they need. The air bag upgrade gives your front axle a 12000 lb capacity but remember it doesn't change the GCVW of the MH.

[speedmerchant]

In real world driving I run 97psi in front right and 94psi in left front. The difference was recommended to me by a truck shop here to help compensate for the crown in the roads here in Ontario. I have never yet run the front tires over 100psi and haven't seen any issues. I did have some weird tire wear that took out a set of front tires but discovered that when I bought the unit from the previous owner, he had it serviced. When they put the wheels back on they didn't center the wheels correctly on the studs and therefore caused the tire to roll offcenter as it spun down the road. Had vibration but the shop said it was just the brakes and that it would go away. Took me two front tires to discover they were wrong.

[tmmar]

James,
I was told that all tires on the same axle should have the same pressure. While it is only 3 pounds difference, I believe that you should have the same pressure in both.
Tom

[speedmerchant]

That would definatley be the case for the rear axles but the fronts run on independent hubs. Not sure why one would tell you that, did they say why?

James

[tmmar]

James,
There is a tire guy who is a Forums member and he posted that. Didn't say why but just said the tires on the same axle should all have the same pressure.
Tom