 Forgeline RS wheels, Trying to make room in the garage |
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 Dec 29 2004, 04:38 AM
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#21
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FRRAX Owner/Admin  Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196  |
11's
279.4 mm = 11" 212.725 backspacing = 8 3/16 66.675 offset for 11's 9.5's 241.3 = 9.5" 174.625 backspacing = 6 7/8 66.675 offset Does that look right to you? 25.4mm per inch |
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Dec 29 2004, 04:49 AM
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#22
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
I was getting 41mm for the fronts and 55mm for the backs, seams kinda off. Did you have these on your fbody before, if not what kinda car were they used/made for?
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Dec 29 2004, 04:53 AM
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#23
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
QUOTE (231go @ Dec 28 2004, 11:49 PM) I was getting 41mm for the fronts and 55mm for the backs, seams kinda off. Did you have these on your fbody before, if not what kinda car were they used/made for? I think my math is wrong. These were used on a firebird. I've never run them, I bought them used and decided not to run them. I did test fit the rear wheel on my F-body and it looks like it will fit with no problems. You could pull your wheel and measure the backspacing. We can convert that to MM and see if it is within tolerances. That may be the most accurate way (since I'm not sure that either of us figured that correctly). |
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Dec 29 2004, 04:55 AM
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#24
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
Im not as worried about the fit as I am them being legal. My car is run in A-Stock and I need a 17x9.5 w/ 56mm front and 17x11 50mm in the rear. Rules say that I can go +/-.25 of an inch, but thats all. I would measure my 17x9.5's, but I don't have any 17x11's to look at. Offset for the front should be at 2.2 and the rears at almost 2 inches.
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Dec 29 2004, 04:58 AM
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#25
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
I knew you were worried about being legal, that's why I was thinking we could measure what you have, I didn't know you didn't have any 11's. Hmmm....
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Dec 29 2004, 05:03 AM
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#26
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
Yeah, I did my oz's which i know are a 17x9 56mm offset and came out w/ 57mm, close enough. And I did all the math the same way we are doing these.
I need it to be around 9inchs deep for the rears and 7.3 for the front. |
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Dec 29 2004, 05:05 AM
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#27
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
We need to be +/- 6.35mm by my math.
Did you measure and calcutate a set of known wheels? Is that what you were saying? |
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Dec 29 2004, 05:06 AM
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#28
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
Yeah, when I measured them I came out w/ 57mm after doing the math. The wheel has 56mm printed on it which is the stock vette size.
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Dec 29 2004, 05:07 AM
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#29
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
Not looking legal for you from what I can see.
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Dec 29 2004, 05:10 AM
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#30
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
Yeah, and you are sure that you measured them correctly? This is going to suck if I have to pass on this.
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Dec 29 2004, 05:11 AM
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#31
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
I layed a steel straight edge (yard stick) across them and measured with a brand new (unstretched) tape measure. I'm sure they are the right numbers.
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Dec 29 2004, 05:15 AM
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#32
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
Just checking, 66mm just seams like a high and strange offset number to me. Thats almost a third of an inch from stock and seams like it would cause some rubbing, i dunno....
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Dec 29 2004, 05:18 AM
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#33
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
I'm going to guess that your math is correct and mine is not. And, if you just calculated known wheels and it worked, I'm going to trust your numbers more than my own.
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Dec 29 2004, 05:21 AM
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#34
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
My Math
9.5- 6 7/8=2.63 * 25.4 =66.6mm 11-8 3/16=2.813 * 25.4=71mm |
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Dec 29 2004, 05:25 AM
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#35
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
Hmmm. He said he ran a small spacer on the rear, but when I test fit them, I didn't see where it was needed (actually, it may have stuck the wheels out past my fender to space them much at all, but firebirds have or seem to have wider fenders).
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Dec 29 2004, 05:27 AM
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#36
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
I don't see how they would have stuck out, wouldnt the 71mm offset be more sunk in than the standard 50mm?
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Dec 29 2004, 05:29 AM
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#37
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
I meant that they would stick out with a spacer (such as a 3/8ths). They look to fit "perfect" on my car as is (I didn't have tires on them at the time) and seemed to be right where I expected them to fit.
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Dec 29 2004, 05:33 AM
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#38
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F-bodyless.... Group: Advanced Members Posts: 243 Joined: 31-December 03 From: Austin, TX Member No.: 77 |
For the backs to be legal I would need over a 3/4 spacer. As much as I hate to say it, but I think im going to have to pass. Unless for some freak reason you got your original numbers wrong, these aren't going to work for me.
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Dec 29 2004, 05:35 AM
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#39
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FRRAX Owner/Admin Group: Admin Posts: 15,432 Joined: 13-February 04 From: Ohio Member No.: 196 |
That is what I was thinking..... Bummer. I know the backspacing measurements are correct. Damn.
I'm off to bed for the evening. |
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Dec 29 2004, 06:31 AM
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#40
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Advanced Member Group: Advanced Members Posts: 439 Joined: 14-January 04 From: Texas Member No.: 128 |
Interested in the math here...
isn't offset calculated from the centerline of the rim? http://www.usacomp.com/Offset.htm |
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