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Discussion Starter · #1 ·
Another question regarding big ass rear rubber. I'm looking to put a set of 275/60R15 (28.2" diameter) tires on the rear on a set of Vision 55 Rally wheels ($100 rebate on Christmas Eve, btw, at Discount Tire).

The wheels are 15x8 with a 5x4.75 BP and -6 offset (4.25" backspace). I think I did my home work correctly, however, since I've had a GTO in my life for less than a year, I wanted to get a sanity check from you all on here.

The suspension was mostly blown out factory stuff. I replaced the springs with "factory height" units from UMI (the UMIs were taller by about a coil or so) and installed new Bilstein shocks all the way around.

Thanks.
 

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Is your rear quarter panel trimmed out to maximize the outer clearance? Along with the inner portions of the wheel well?

I'm chasing the same decisions as you right now, thinking of the same rear tire and wheel sizes. I am following @lust4speed 's advise here...

(1) Largest tire for a 1966 GTO | Pontiac GTO Forum

He told me his front tires are Cooper 235/60R15, but I don't know if you can go larger up front. I have not cut my quarters out or taken all the neccesary measurement yet, but plan to order a rear diff with custom width to center my wheels.
 

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The 4.25" backspace is almost an inch farther out than optimum, and the tire will not clear with the stock width '67 axle. I'm running a custom Wheel Vintiques steel rim that is 15x8 with a 5.25" backspace and that sets the wheel centered between the trimmed outer fender and the frame on the inside. After trimming the outside lip and tapping in the inner fender above the frame rail, the available space is almost exactly 12" and a 275/60R15 tire on an 8" rim is 11". This gives a half inch clearance on each side of the wheel. If you have a 1/2" clearance to the outside and move the wheel out 1" nasty things are going to happen.
 

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The 4.25" backspace is almost an inch farther out than optimum, and the tire will not clear with the stock width '67 axle. I'm running a custom Wheel Vintiques steel rim that is 15x8 with a 5.25" backspace and that sets the wheel centered between the trimmed outer fender and the frame on the inside. After trimming the outside lip and tapping in the inner fender above the frame rail, the available space is almost exactly 12" and a 275/60R15 tire on an 8" rim is 11". This gives a half inch clearance on each side of the wheel. If you have a 1/2" clearance to the outside and move the wheel out 1" nasty things are going to happen.
What did it cost to get the custom backspacing done on the wheels?
 

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Cameo Ivory 1967
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I was at a car show over the summer, and the guy had that same tire size. I LOVED IT!!!!!! I was so excited to hear that he put them on, without any suspension mods... then I looked underneath and saw load leveler shocks.

People suck, but yeah, they wont fit.

I have your same spring and shock combo, and I run 235's. I think 245 would easily fit to, but you cant just go up in width, aspect has to change, too.
 

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What did it cost to get the custom backspacing done on the wheels?
It's been quite a few years since ordering. I do remember that the custom steelies were about the same as ordering out a Rally II wheel from them. My blue GTO came with the poverty caps and I made up my mind to return to the look after having at least a half dozen different wheels on the car over the years. Ordering the wheels and dog dish caps today can now drive you into poverty. I can remember that I talked to the Wheel Vintiques tech and had all my information including a custom order number from them, and then with their blessing I placed the order through Summit. At that time Summit wasn't charging sales tax and Wheel Vintiques was located a few hours away from us in SoCal. At the time going through Summit saved the 8% sales tax and their price was better, and the wheels were drop shipped from the California warehouse to my door anyway. I also opted for the black powder coating and the wheels still look like new and would do that again.

My last attempt to use W.V. for the Catalina wagon project wasn't successful. I don't know whether it was the specific tech I was talking to or the company has had a policy change, but they really were not that interested in going outside of what was available from their catalog. We ended up going with an American racing wheel that had acceptable backspacing from Summit. Ended up with a 17" chrome Torque Thrust D 8" wide with a 5.1 backspacing. Summit site worked great and started with over 6,000 rim choices and each selection narrowed the field on each choice until I could choose from 3 wheels. Two were exactly the same except for polished or chromed aluminum, and the third choice is one that I really wanted since it had a 5.25" backspace instead of the 5.10" but the price doubled for that choice and I didn't want to pay that much. Anyway, for the Catalina Safari the chosen rims look better. I tried the poverty cap look by borrowing my caps off the GTO but on the wagon it just didn't look that great.
 

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Idk if this is any help and don't know what wheels you're interested in but I have MT 275/60/15 drag radials on the rear of my stock height '65 but did a little trimming, wheel is an American Racing VN501 8"-4.5 BS. They have it in a 17" with a 5 and 5.47 BS. which I have considered. Front has 1" lowering springs with 215/70/15 15×7 4" BS
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1965 BOP rearends were 1" narrower in overall width. That changed about mid-way into the 1966 model year. So that 1/2" narrower per side with a 4.50" backspace would be equal to a later rearend with 5" backspace. That does bring up a good point that if the '66 in question had the narrower rearend, then it could get by with less backspacing.
 

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Here's a simple search on the Summit website for all 15x8 wheels with backspacing between 5" and 5.25"

Summit wheel search

Further narrowing of the search criterial would remove choices you wouldn't consider. Also, about two years ago two of our club members ordered out Wheel Vintiques 15" Rally II wheels with the custom 5.25" backspacing for their GTO's.. Those turned out very nice.
 

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1966 hardtop yellow black top factory auto with a/c 4v
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i have 275/60 -15s on rear of my 66 i have 15x7inch rally 1 wheels from ames if i remember right they are 4and 1/2 back space i have 15x6 on front with 205 75 15 red lines from black tie have delco air shocks on rear with very little height difference not any crazy 90lbs or anything and i have all kind of room 2 adults one kid in rear seat no problem
 

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Cameo Ivory 1967
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i have 275/60 -15s on rear of my 66 i have 15x7inch rally 1 wheels from ames if i remember right they are 4and 1/2 back space i have 15x6 on front with 205 75 15 red lines from black tie have delco air shocks on rear with very little height difference not any crazy 90lbs or anything and i have all kind of room 2 adults one kid in rear seat no problem
Congratulations, but I do find it hard to believe, unless someone put bigger springa at some point? Post some pics if you can, I'd like to see how high it sits. Ive been wanting 275's forever.
 

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i have 275/60 -15s on rear of my 66 i have 15x7inch rally 1 wheels from ames if i remember right they are 4and 1/2 back space i have 15x6 on front with 205 75 15 red lines from black tie have delco air shocks on rear with very little height difference not any crazy 90lbs or anything and i have all kind of room 2 adults one kid in rear seat no problem
Do you know how wide your rear differential is from where the wheels make contact? And a good number for the backspacing is critical.

The only Rally II wheels Ames has in the 15x7 is with a 4" BS. The 15x8 are only available with and 4-1/2" BS.
 

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1966 hardtop yellow black top factory auto with a/c 4v
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i will check maybe they are 4inch back space i will check that and rear end withe and hopefully sat my 15 year old granddaughter can take pics i will am going with my car sat so by sometime later sat for them i have no clue on how to do them i still use a flip phone and really wish i could carry an old rotary
 

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sorry i took so long posting this forgot about new years my rear wheels are 15x7 part#c-5803-257a from NPD i do believe they are 4 inch back space i checked my 66 space the rear is 26" high ground to w/o mldg 3''between side wall and w/o opening with Delco air shocks 60lbs of air front is 23.5 "high 3" from side wall to w/o openin g mldg. and i do need to replace front springs someone put those spacers that you turn with a braker bar in them i have springs that is winter job i have diamond back red lines 205/75/dbirl on front 275/60/15/ssrl on rear plenty of room every where oh the rear end is original
 

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Discussion Starter · #19 ·
I ended up going with wheel vintiques rally 1s with a 5" backspace. 275/60/R15 BFG TAs out back. No rubbing on the fender, but my exhaust was touching the sidewall, so I cut that off (previous owner did a crap install job anyway). Got 215/70/R15s up front. Previous owner had 245s up front that somehow survived all the rubbing.
 
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