Backspacing question.

I have a couple of questions about backspacing on wheels. I understand that it changes the offset of the wheel in comparison to the rim and where it mounts. But not sure how much I need or in what direction. I
have an 89 s10 4x4 with a 2" lift and stock 15X7 rims. I dont know what the stock backspacing is. However I have 31s on it they fit great but rub a little on the sway bar I think it is at full turn. I plan on getting new rims in the near future 15X8 and was wondering what backspacing would be recommended to help correct the rub. Thanks
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Negative 1/2 inch should do it
John
wrote:

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On Tue, 08 Aug 2006 11:33:03 GMT, John

Just remeber that went ever you change the back space to move the wheel out further you increase strain on axle and suspension and effectrivelyly reduce it capacity because a higher stress is placed on it at same load level. ----------------- TheSnoMan.com
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wrote:

Only partially correct. Go by the percentage of backspace, not actual numbers. I stock is 75% for a 7" wide rim for a 5.25" backset and you want/need to go to 9" wide rims you want a 6.75" backset. This keeps the original balance and stress factors of the setup. Engineering 101.
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On Tue, 8 Aug 2006 19:43:49 -0500, "Mike Dobony"

I think you need to retake the course. When a wider tire needs to be displaced further outwards from chassis so that it does not rub, you might argue that the stress has not changed because the inside of tire is about the same place relative to frame and pivot axis. The problem with this is that the line of the load center through the tire itself had been moved away from vehicle which increases leverage against the suspension and the outer edge of tire is even further out from pivot axis due to increased width which ads to stress too. No free lunches here. ----------------- TheSnoMan.com
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wrote:

You are talking about a different issue, fit. Most trucks will accomodate wider tires without the rubbing problem. You can keep the load center in the same place and this will not add undue stress to the system. This will not cause the problems you describe. But now you insist on enlarging the issue wiht tire rubbing and changing thet load center. In this instance I agree. In this instance in order to accomodate a too wide tire you need to change the load center and then add undue stress on the suspension, to the point where it can become unsafe. Moderately wider tires with moderately wider rims, keeping the load center in the same position does not add stress.
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On Sun, 13 Aug 2006 15:26:53 -0500, "Mike Dobony"

Wider tires with same load center still do add extra stress to front end and steering linkages. Maybe not as much as a outset wheel but they do add stress none the less. I keep my work trucks a long time and I use stock type tires on them and I never have any front end problems. Put some big rubber on a checy IFS front end and you will be replacing ball joints sooner for sure. How much sooner depends on tire size and how you drive. Poeple tend to think of truck and 4x4's as to being mechanically immune to the effects of bigger tires but they are from reduced braking capacity, (increased leverage for brakes to overcome) reduced power from a taller effective drive ratio (if you do not regear and possible shorter tranny life too without also regearing ) reduced MPG from added drag and reduced componenet life. ----------------- TheSnoMan.com
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