rim-tire fit

[66 twins]

Just picked up tire for mock-up. now its 33x12.5x15 I have 15x8 rim thornbird tsl printed on tire < mount on 15x10 rim > IS THIS A RECAMENDATION or it can't be used on a smaller rim??

[pippinmader]

Re: rim-tire fit

I would have no problem running it on a 8 inch rim, although you should keep in mind that it changes the angle of the bead to the rim, which might make it come off the bead easier at low pressures.

[71BRONCO71]

Re: rim-tire fit

Ive always ran 8" rims.. Never lost a bead yet.

[66 twins]

Re: rim-tire fit

thanks needed a second on that ,we wont be crawlin much so air down not a problem for now, that is till I change our minds later.

[TBS-POPS]

Re: rim-tire fit

the thornbirds , because of the tread design and pattern need to be run on the designated size rim printed on the tire. the square flat design will only run good on the 10" rim.

[tortuga]

Re: rim-tire fit

what are you looking for out of the mock-up? I think this might give you some bad info on tire clearance.

If I am looking at this right, a 15" wide tire centered on an 8" rim is going to put the inside of the tire a lot closer to center of the vehicle than what you might be running in the future. Same tire on 10" rim would be 1" farther out, a 12.5 on a 10" rim would be maybe like 4 inches farther out.

[jamesroney]

Re: rim-tire fit

what are you looking for out of the mock-up? I think this might give you some bad info on tire clearance.

If I am looking at this right, a 15" wide tire centered on an 8" rim is going to put the inside of the tire a lot closer to center of the vehicle than what you might be running in the future. Same tire on 10" rim would be 1" farther out, a 12.5 on a 10" rim would be maybe like 4 inches farther out.

Actually, the same tire on a 10 inch rim would start 2 inches farther out. You are going with the assumption that a 15x8 and 15x10 are both centered on the rim. But they are usually NOT, and nearly every major manufacturer holds the backspace constant, and lets the entire rim move outboard.

This is because the backspace is constrained by things like brake calipers, tie rods, and other suspension components. But there is no such constraint going outboard. So if you have a 15x8 that is flush with your warn locking hub...a 15x10 will stick 2 inches farther out.

Of course I'm assuming that you are not building custom offset wheels, and you are going with what is commercially availalble by US wheel, American Racing, Eagle Alloy, Cragar, ProComp, Centerline, etc.

I am actually LOOKING for a set of 15x10 wheels with a 5 inch backspace. Haven't had any luck yet.

[earlybronco72]

Re: rim-tire fit

James I have some old centerlines I just rook off. I will check the back spacing. I don't think they are five inch though.

Actually, the same tire on a 10 inch rim would start 2 inches farther out. You are going with the assumption that a 15x8 and 15x10 are both centered on the rim. But they are usually NOT, and nearly every major manufacturer holds the backspace constant, and lets the entire rim move outboard.

This is because the backspace is constrained by things like brake calipers, tie rods, and other suspension components. But there is no such constraint going outboard. So if you have a 15x8 that is flush with your warn locking hub...a 15x10 will stick 2 inches farther out.

Of course I'm assuming that you are not building custom offset wheels, and you are going with what is commercially availalble by US wheel, American Racing, Eagle Alloy, Cragar, ProComp, Centerline, etc.

I am actually LOOKING for a set of 15x10 wheels with a 5 inch backspace. Haven't had any luck yet.

[tortuga]

Re: rim-tire fit

Actually, the same tire on a 10 inch rim would start 2 inches farther out. You are going with the assumption that a 15x8 and 15x10 are both centered on the rim. But they are usually NOT, and nearly every major manufacturer holds the backspace constant, and lets the entire rim move outboard.

If the backspace is constant, wouldn't the inner side of the rim be in the same plane as before? I figured the tire would move outward by 1/2 of the increase in width as the center of the tire would only move that far.

[jamesroney]

Re: rim-tire fit

Tortuga,

Of course you are correct. Sorry about that. I had confused TRACK with stickout. Center of tire moves an inch, track increases by 2 inches, and total width is increased by 4 inches.