measuring for wheel and tire

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twayne24365

twayne24365

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so i have searched the internet and can not fing a clear straight-forward answer.
how do i measure to find out what backspace i need to center a 15x7 wheel in the wheel well. the car is a 1972 dart swinger, all suspension is stock, thanks
 
Take stick and lay it across the rim (laying on the rim lip/edge) then take ruler/tape measure and measure the distance between the hub and the stick. That is your backspacing of the rim.

To do the wheel well its the same basically. A stick from the axle hub to the top of the wheel well then measure distance from stick to the leaf spring (should be the closest point to the axle hub unless you have changed their location) or the wheel well (whichever is the shortest distance). Write that number down, this gives you the backspacing. Then measure from leaf spring/inner wheel well to the outer wheel well and that will tell you how wide of a tire you can have in your wheel well.
 
thanks, the car came with 14x7 centerlines and used a 5x4 to 5x4.5 adapter and the wheel rubs the outer wheel lip pretty bad, i just want to make sure i have all the right measurements before i buy new wheels
 
Well you could ditch the adapters and order the axles at 4.5 (or have your stock ones re drilled) or keep the 5x4. Either way this will reduce your backspacing and should make your wheel choice a little cheaper.
 
Yea, i was planning to get the 15x7 in sbp from summit, they are plain steelies at only $98
 
A '72 Swinger with the stock suspension and no adaptors with a 15x7" rim? What rear axle? 8 3/4?

Typically, with the stock suspension you want pretty close to a "zero offset" rim on the Darts. For a 15x7" that would be a 4" backspace. If you have an 8 3/4 you can get away with a little more backspace than that, say 4.25". The 7.25" rears are a little narrower, so stick with 4" for them.

With the stock spring locations the biggest tire you'll fit in there is a 255/60/15. But of course every one of these cars is a little different, so measuring is still the best bet.
 
Yea, its an 8 3/4 with sbp, i measured it this morning and 4" backspacing would be perfect, thanks guys
 
I would draw out a diagram, and as above. Don't forget that the wheel well for lack of better description, tapers towards the top. Don't forget that there IS some flex, hard cornering, etc

The reason there is not a "hard and fast" answer is that first, OEM axles are different over the years, and 8 1/4 are typically different width than 8 3/4

Many of us have swapped one for the other, newer for older, etc, so "what the car was" "is not what it is now."

In my case, I run a Lincoln Versailles 9" so nothing is "as it seems."
 
I just put 255/60r15s on the back of my dart, they fit but its tight. The rims I used were 15x8 4.5 backspacing.
 
Get the Percy's wheel measuring tool. Measure once. Buy once.
 
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