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Wheel/tire width, offset, backspacing?
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oldhippie
Posted 2017-06-07 5:43 PM (#541730)
Subject: Wheel/tire width, offset, backspacing?


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Posts: 131
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I've measured the rear wheel well openings(drum surf. to inner fender lip, drum to leaf spring retainers/clamps?) and once I get my e-body axle installed, I'll have a minimum of 6.5" clearance on either side. I haven't been able to find any used rims yet, so I may have to consider new. What I'm wondering is, how much flex, typically, is in the suspension?

If I buy new, I'll be going with a lower profile tire, with the same OD, so I won't have much sidewall flex (I think)? Stock tire diameter for the New Yorker (my current drivetrain) was 29.3 according to this website, and I've matched the sure-grip I installed in the e-body axle as well (2.76 gears).

Rim/tire combination I'm considering (unless I find something used locally) is an 18x10 rear rim, zero offset, with 255/55's with a cross-sectional width of 10" (assuming that's the patch width, not the sidewall max). That gives me an overall OD of 29" (235/75 R15 is 28.9") and an even split of the overall 11" rim width (5.5" either side of the mounting face). This plan gives me 1" of clearance on both fender & suspension sides. Is this enough?

Front rim would probably be 18x8, 235/60's (OD of 29.1") with the same cross-sectional width as the 235/75 R15 of 9.3"

Is there anything I haven't considered that you think I should be aware of? I do plan on having the front end rebuilt eventually, and don't plan on driving much until I do (once it's running, that is). If my logic for this is sound, I may try to find some other used rims that may work. (FWIW, I called 3 wrecker yards near me & none of them had 15" dodge/chrysler rims that old, and all of the newer rims styles have 1.5-2" of positive offset.)

Edited by oldhippie 2017-06-07 5:45 PM
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Powerflite
Posted 2017-06-07 9:27 PM (#541748 - in reply to #541730)
Subject: RE: Wheel/tire width, offset, backspacing?



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You didn't say what car this is going on. It does make a difference. But for reference, here is my '58 dodge. I have 275x60x15 tires on the back with 8" rims and zero offset. They fit quite well, but I seriously doubt that you could fit a wider tire than this one under there. Your 12" width number doesn't sound right to me. When I measured mine, I believe I had a little over 11". But yours may very well be different than mine. If you indeed have 1" of clearance, that is plenty. You can get away with 1/2" if it is higher up on the tire. The lower it is, the more clearance you need. On the front, I have 255x60x15 tires on the same 8" rims with zero offset. They work well, but do rub slightly when turning sharply while going over a large bump. But it isn't a common situation to need to worry about it. I purchased these rims from Wheel Vintiques.



(LRCoronet.jpg)



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Attachments LRCoronet.jpg (244KB - 168 downloads)
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oldhippie
Posted 2017-06-08 10:18 AM (#541786 - in reply to #541730)
Subject: RE: Wheel/tire width, offset, backspacing?


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Posts: 131
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Thanks for the reply! I like the look of your setup, that's about what I'm going for. If only I could find used zero-offset rims...

I've got a '60 Dodge Matador. Measurement with the stock rear axle (60.625" width) is 6" clearance from the drum surface to the the leaf spring retainer? (on mine, this is right about at the distance of the 14" tire OD - might not matter with the larger rim) - 6.25" to the leaf itself. I measure 7" from the drum surface to the innermost point of the fender lip. The e-body axle I'll be installing is 1" longer overall (61.625" width), which puts each drum surface out 0.5", which is how I came up with the 6.5" each side (13" wheel well clearance, not 12").

Edited by oldhippie 2017-06-08 10:21 AM
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StillOutThere
Posted 2017-06-08 1:25 PM (#541798 - in reply to #541730)
Subject: Re: Wheel/tire width, offset, backspacing?



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Location: Under the X in Texas
I'd recommend borrowing or buying a "Percy's WheelRite" which will provide you all the measurements. An amazing tool created around 7-8 years ago for rodders and muscle car guys to absolutely max out wheel and tire, front or rear. Ask around at local performance shops if they have one. Or they are online, even Summit /Jegs sell them as I recall.
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oldhippie
Posted 2017-06-09 9:45 PM (#541879 - in reply to #541730)
Subject: Re: Wheel/tire width, offset, backspacing?


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Posts: 131
10025
Thanks for the suggestion. How helpful would that be without the ability to put weight on the suspension to check clearances, e.g on the front?? Seems like there's a possibility for it to be misleading with the suspension extended (jack under frame)?

The TL;DR version of my post is essentially this - is 1" clearance inside & outside enough that the suspension flex won't be an issue, i.e. is the suspension shift/sway during more aggressive cornering less than 1" for the rear?
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StillOutThere
Posted 2017-06-10 8:18 AM (#541892 - in reply to #541730)
Subject: Re: Wheel/tire width, offset, backspacing?



2000100010010025
Location: Under the X in Texas
Measurements are with the wheel /tire off the car and yes, you need to support the rear axle with a stand of some sort and the front similarly.
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