Change in rim width = change in offset?

[JDP]

I am investigating some off-road tires for my jeep. Current tire size is stock 235/75/15 on stock 15x7 rims with a 1.25 positive offset.

I could go to the 30x9.5 size but would prefer the 31x1.5 on a 8.5 rim.

How much change in offset is necessary, safe, and workable for the increase in tire width??

Thanks

JD

 

[shortyb]

If its possible, you'll want to increase offset IDEALLY at half of the increased width. Ie: you increase rim width 1.5 inches, you should add .75 offset. This keeps the steering axis at the same spot. Now if suspension components of other structures prevent this, obviously you will have to keep the same offset albeit with a wider rim. Generally the only caveat with this is it can make the steering feel heavy, especially with larger tires.

 

[wulimaster]

Toyota pickups with 31x10.5 tires come with 7 inch rims. Perhaps your stock rims are only 6 inch. I ran 31x10.5 on 8 inch rims and I didn't see the need other than I was running 30x11.5 when I got the 8 inch rims. I was only able to go up to an 8 inch rim for my particular vehicle and still maintain the correct offset.

If your rims are really 7 inch then 10.5" will fit fine on the tire. Maybe not on the vehicle though.

[ May 16, 2005, 11:24 PM: Message edited by: wulimaster ]

 

[JeepZJ4.0]

quote:

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Originally posted by JDP:
I am investigating some off-road tires for my jeep. Current tire size is stock 235/75/15 on stock 15x7 rims with a 1.25 positive offset.

I could go to the 30x9.5 size but would prefer the 31x1.5 on a 8.5 rim.

How much change in offset is necessary, safe, and workable for the increase in tire width??

Thanks

JD

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31s fit on the 15x7 inch rims that come on Jeeps. Any larger and you're going to want to go to 15x8s. I've seen someone mount 33s on 15x8 TJ Canyon rims.

 

[JDP]

looking at the bridgestone dualler spec sheet for the 31's shows a 7 to 9" rim width range.

My thinking was that the minimum width would be the least preferable to use.

The jeep had 31x10,5's on it when we first looked at it and test drove it before we bought it. It rode like it was on balloons. I figure putting the bigger tires on at least 8" rims would settle that down some.

Those big tires rubbed a bit on the control arms and sway bar so I calculated that a back space of about 1/2 inch would accomodate the increase in width and keep rubbing to a minimum.

Any other comments and experiences would be appreciated.

JD

 

[Brian Miller_dup1]

quote:

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Originally posted by JDP:
looking at the bridgestone dualler spec sheet for the 31's shows a 7 to 9" rim width range.

My thinking was that the minimum width would be the least preferable to use.

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This is exactly the reason that I got new 15x8 wheels for my Ranger. The stock 15x7s had P235/75-15s. When I moved up to 31x10.5R15s, the 7" wheels are a little narrow. I know they are speced for 7 to 9", but I think an 8" is better (that is also the recomendation on the Ranger forum that I frequent where most everyone has upgraded to the 31" tires).

My $0.02
Brian