Hate to do this ... Wheel question - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 04-17-2012, 12:13 PM Thread Starter
 
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Hate to do this ... Wheel question

I searched I promise. Couldn't find anything that really fit.

69 Custom-S 4 wheel disc breaks, stock but recently refreshed suspension.

I have been looking around for wheels since this restoration started because my car came with what I consider to be cheap ugly wheels. I would be happy with Rally II's or even Honeycombs but the wife is not a fan of any of the stock Pontiac wheels of the era.

That said, I would like to go with 17's myself and I actually found some nice 17 inch wheels that look kind of like the old Hurst wheels, they are 17x8 with 4.89 backspace and a +10 offset. >fairly certain that will fit<

So here's my 2 questions.

1. What is the backspace and offset of the stock 15x8 Rally wheels?

2. What size tire could I get on a 17x8 wheel up under stock wheel wells?

Thanks as always.
S

2005 GTO Daily Driver
1969 Custom-S Project car

1971 GTO 455 in process of rebuild TH400 NEED A NEW REAREND!!!
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post #2 of 7 (permalink) Old 04-17-2012, 03:35 PM Thread Starter
 
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No responses yet.

Well here's what I have come up with.

Original tire was the equivalent of 225/70/14 (or there about)

That's 8.85 inches wide with a total diameter of 26.4 inches (though I have heard that the original tire/wheel combo came in at about 27 inches.) So we'll say give or take half inch.

With 17 inch wheels they recommend 225/55/17 for the same width and an overall diameter of 26.74 inches.

I have 275's on the back of the 2005 GTO and can't see going smaller than that on the 69 so I am thinking of this combo.

275/50/17 width of 10.82 in. overall diameter of 27.82 in. REAR
255/50/17 width of 10.03 in. overall diameter of 27.03 in. FRONT
Tires would be Nitto NT450 (only matched set I can find in these sizes)

I'd be within an inch of stock height all the way around and a bit more rubber to the road.

I know she has 275's on her right now in the back but they are 15's so I have no clue if this will work, and since I still don't know the original backspacing and offset on the stock 15's (or the crappy custom wheels I have now) I still have no idea where I am at in the fender well.

Anyone?

2005 GTO Daily Driver
1969 Custom-S Project car

1971 GTO 455 in process of rebuild TH400 NEED A NEW REAREND!!!
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post #3 of 7 (permalink) Old 04-17-2012, 05:21 PM
 
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Could go to a tire shop and ask for a test fit, the sizes you mentioned sound like ones I have seen in the forums before but I can't be certain. Try googling "275 50 17 on a gto" or something like that. Bump
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post #4 of 7 (permalink) Old 04-17-2012, 06:14 PM
 
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you may be pushing the envelope on the front especially if you lower it. Billet specialties makes some nice 17" rally type wheels (not cheap) i picked mine up used off a trailer queen. I will never have another chrome wheel again, hit them with a mothers ball and they will blind you in the sun. I jumped on them because from a distance they look like Cragars but close up they look more like arrowheads and the detail fluting matches the ribbed tail panel and the console


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post #5 of 7 (permalink) Old 04-18-2012, 10:20 AM Thread Starter
 
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Here's the wheel I am looking at.



They also have it chrome but I think I like the subtle nature of the gunmetal.

And after looking at the front wheel/tire combo on her now I am re-thinking the front tire size as well. (thanks for the heads up Instg8er)

Prolly be smarter to go 235/60/17 up front, that's 9.25in. wide with a total diameter of 28.1in.

with the 275/50/17 in the rear (10.82in. wide 27.82in. diameter) the sizes will be a tad taller than stock but I think as long as the backspace and offset are where they need to be I will be cool.

Anyone got the stock numbers for the rallys? 15x7 or 15x8 or even the 14's just need a measurement for backspace and offset stock so I can use my calculator and see where I am.

Thanks all!

2005 GTO Daily Driver
1969 Custom-S Project car

1971 GTO 455 in process of rebuild TH400 NEED A NEW REAREND!!!
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post #6 of 7 (permalink) Old 04-18-2012, 05:03 PM
 
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No problem i am running 235's with only a slight rub when backing out at full turn but the wheel wells on the 66' are a bit less forgiving so you should be fine...why dont you just check your rims for offset....then check clearances on shock etc. on the inside and lip on the outside, what you want is the new rim centered between your obstructions then measure between them and you will want the tire at least 1-2" narrower than that measurement to account for some bulge of the sidewall. i think we came up with 4.5 - 5" backspace was ideal on another thread.

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post #7 of 7 (permalink) Old 04-18-2012, 07:46 PM
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Look to beg, borrow or steal a Percy's wheelright to find optimum backspace and tire size. I run a 12.5x29x15 in a stock wheelwell with 6" backspacing. Lots of people ask if I've minitubbed but it's not.

http://www.percyshp.com/WheelRite.html
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Wheels & Tires

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