Wheels Size on 1966 Pontiac Tempest/GTO [Archive]

garthed

12-19-2009, 01:16 PM

I'm new to this forum and sure glad I found it. I just purchased a 1966 Pontiac tempest that still has the stock wheels. I would like to replace them with either 17s or 18s. I'm leaning more towards 18s. The suspension is all stock exept for rear air shocks and it has drum brakes.

My question is what offsets and back spacing should be looking for in a wheel and what size tires. I am looking at a set of Boss 338 18 inch and I think they are 9 inches wide.

Also if anyone has a recommendation for lowering springs or wheels and a good place to by them let me know.

Edit, I just got more info on the wheels that Im looking at. The front is an 8 inch with a -4 offset and 4.5 in back space. The rear is 9.5 inch with 0 offset and 5.25 backspace. Tires would be 245/40/18 and 275/40/18 rear. Does this sound correct. I do not want the car to look funny.

Thanks again.
Garth

ProdigyCustoms

12-19-2009, 01:58 PM

LeighP

12-19-2009, 02:44 PM

An 8" rim with 4.5" backspace would be 0 offset - thats the same as factory WS6 Pontiac alloy wheels (2nd gen).

wmhjr

12-19-2009, 03:50 PM

I think you might have issues on the front with an 8" wide, 4.5" BS on a stock '66. I'm running 5" BS on 18x8 in the front. Of course, my suspension is far from stock. Problem areas on the '66 will be the bottom rear lip of the front fenders. You may also have A-Arm issues. You need to consider what brakes you'll be using, and tire diameter as well as wheel size. There's not much room on a '66 Pontiac A-Body.

On the back I'd be real surprised if you didn't have issues with 9.5" wheels at a 5.25" bs and 275s on a stock car. You need to check the inside of your wheel houses in the back. You'll see that there are actually inner "ledges" that further restrict the available width both on the inside and the outside. With a stock type suspension and especially with air shocks, you're going to have some lateral movement also. I'm running 18x10s in the back with 6.25" bs and 275s and there isn't much extra room even on my car - which has some serious suspension and driveline upgrades to stabilize the rear end - and which I've modified the inside of my wheel houses to remove those restrictions and create more available space.

67 goat

12-29-2009, 10:13 AM

You wont clear a 9.5 on that car. You need a maximum of a 9.

We can help with a couple lowering solutions. Feel free to cal

Our holiday hours are Sunday 12PM to 8PM, Monday though Firday 8AM to 8PM, Saturday 8AM to 4PM

I'm running 17x9.5s in the rear with a 285/40. The fronts are 245/45s on a 17x8 with 4.75" backspacing. Rear backspacing is huge at 6.375". I'll admit it's tight, but it just fits. Rolling the inside of the fender lip and slightly less backspacing would make them fit easier. If I have 3 people in the car and bring it just to the point of oversteer, I do get a tiny bit of tire rub on the inside. Otherwise, it's perfect.

Up front, I'm running lower control arms from SC&C but I forget the brand. They move the tire forward about 1/2" I think, otherwise they would rub the bottom rear lip of the fender as wmhjr pointed out.

gearheads78

12-29-2009, 12:18 PM

One thing you need to know when talking 66-67 A-body rears is the axle width. You need to know what you have and what the person advising you has. For instance I have personally seen 66 Lemans and 66 Cutlass from the factory with wide like a 68 Chevelle comes with and narrow like a 66 Chevelle width. Its only apox 1/2" per side it makes a difference when you are dealing with close clearance. I have 18 x 10 with the wide rear and a 285-40-18. My BS is 6.625" with ls1 rear brakes on the Cutlass. If I was even a 1/4" wrong on BS I would be rubbing.

wmhjr

12-29-2009, 01:37 PM

gearheads78 is right. To take it a little further, if you're getting THAT close you need to really look yourself. There can be all kinds of variation side to side. You also need to remember that based on the suspension, you're going to get further variation while driving. I can tell you I have as much room as you can possibly get with a '66 in the back without notching the frame or flaring the wheel wells. The rear wheel house modifications we did opened it up flush with the frame. I'm also running Currie rear suspension on a Moser rear end. So, deflection will be the minimum possible you'll get on a '66 with a 4 link suspension. I could have squeezed 295s - but it would have been closer than I would be comfortable with. With you running air shocks and stock suspension, I'd be real nervous.

ProdigyCustoms

12-29-2009, 02:43 PM

Here is a 67 GTO we are doing right now. The frame is out and there is no rear, but here is the tire and wheels mocked up in the hole. This as a 19" X 9" with a 275 tire and it is STUFFED! We originally built these wheels as 10s and it was hopeless no matter what size tire (that would fit the rim) we tried. This car will still probably rub a tiny bit in fully loaded spirited driving scenarios, but nowhere slicing / cutting will be a concern.

Also, to get the deep lip we are narrowing the rear 1 1/4" per side. Also changing the housing ends to 3.15 bearing Ford Ends for better side load abilities.

Also as mentioned, measuring exact rear end width is critcal on these years. Believe me, I am livinig this right now.

https://static1.pt-content.com/images/noimg.gif

Nicks67GTO

12-29-2009, 03:09 PM

I'm running 17x9.5s in the rear with a 285/40. The fronts are 245/45s on a 17x8 with 4.75" backspacing. Rear backspacing is huge at 6.375". I'll admit it's tight, but it just fits. Rolling the inside of the fender lip and slightly less backspacing would make them fit easier. If I have 3 people in the car and bring it just to the point of oversteer, I do get a tiny bit of tire rub on the inside. Otherwise, it's perfect.

Up front, I'm running lower control arms from SC&C but I forget the brand. They move the tire forward about 1/2" I think, otherwise they would rub the bottom rear lip of the fender as wmhjr pointed out.

PM sent with a few questions about your GTO

67 goat

12-29-2009, 05:28 PM

PM sent with a few questions about your GTO

Sent a response, but couldn't figure out how to attach pics in a PM.

4. I guess I like the angled shots because I don't really have any pics of the entire car straight from the side.

Here's some close-up of the front and rear, before and after. This was right after I installed everything though.....things have settled a bit since.....probably another 1/2" or so.

67 goat

12-29-2009, 05:31 PM

A couple more shots, before and immediately after....in the garage. Doesn't even look like the front dropped at all in these pics! But it's definitely settled in the front now.

cwylie

12-30-2009, 08:07 AM

I was told by coys these would fit.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=310180880917&viewitem=

MANUFACTURER
COYSWHEEL.COM

FINISH
CHROME

FRONT SIZE
2-18X8

BOLT PATTERN
5X4.75

BACK SPACE
4.50"

REAR SIZE
2-20X10

BOLT PATTERN
5X4.75

BACK SPACE
5.50"

wmhjr

12-30-2009, 11:27 AM

Good luck with that. Coys may have said it fits. I can tell you first hand that my '66 Pontiac would not permit those sizes without the mods I've done. Absolutely no possible way.

ProdigyCustoms

12-30-2009, 02:28 PM

Good luck with that. Coys may have said it fits. I can tell you first hand that my '66 Pontiac would not permit those sizes without the mods I've done. Absolutely no possible way.

Amen!

cwylie

12-30-2009, 04:09 PM

Damnit!

Amen!

66goat

01-17-2010, 07:24 PM

wmhjr

01-17-2010, 07:45 PM

I just put a set of Coy's on my 66. I rolled the lip and made sure the metal work above the frame rail was flat and smooth. The rear are 20x10 with 5.75 bs and I am running a 285/30 BFG G Force KDW 2 and they fit perfect! Here are a couple pics.

Not to rain on your parade, but have you looked above the inside lip on your wheel wells or on the inside above the frame? Unless you have a very unique '66, I would bet serious cash that when you compress that suspension and in particular if you go in any direction other than a straight line, you'll have clearance issues. You'll be rubbing that rubber. The lip is not the problem on '66 and '67s. The step above the lip is. If you have made the same wheelhouse mods that I have, you can fit those wheels and tires (though the BS makes no sense.

From my perspective the rear wheel on your pic does not look like it has any clearance at all. Even with significantly and seriously upgraded suspension on our cars, you need a bare minimum of 3/8" per side of clearance for deflection. There's another thread in this forum from a couple days ago referencing what happens when you don't.

DriverzInc

01-18-2010, 09:32 AM

Not to rain on your parade, but have you looked above the inside lip on your wheel wells or on the inside above the frame?

This is the same issue we have run into on the a-bodies. On Johnny's 67 Tempest, he actually cut out this "hump" on the outer fender above the pinch weld. This allowed us to run a 20x10 with a 275/ wide tire.

On my 66 Chevelle, I ran 20x10 Rushforth Wheels, 6.25" backspace, with a 285/30/20, 10 bolt rear end, Varishock single adjustable shocks, front and rear sway bars from Hotchkis, and 3" lowering springs from OPG. I never had a problem with it either.

I think the most important thing is to measure twice, cut once.

wmhjr

01-18-2010, 09:47 AM

This is the same issue we have run into on the a-bodies. On Johnny's 67 Tempest, he actually cut out this "hump" on the outer fender above the pinch weld. This allowed us to run a 20x10 with a 275/ wide tire.

On my 66 Chevelle, I ran 20x10 Rushforth Wheels, 6.25" backspace, with a 285/30/20, 10 bolt rear end, Varishock single adjustable shocks, front and rear sway bars from Hotchkis, and 3" lowering springs from OPG. I never had a problem with it either.

I think the most important thing is to measure twice, cut once.

Yup. I believe that inside "hump" or "ledge" is more prevalent on the ponchos than for the chebbies IMHO. I also cut it out like Johnny did, but I did so on both sides (inside and outside of wheel well). I actually could probably run a 295 now but it would be VERY close tolerance and under cornering forces, it would likely rub. While I could have fit the 10" wheels in the wheel well without doing this, it would only have been when the vehicle was standing still. It would not be safely drivable.

BTW Jon - I'll send you some pics next week. The car will be at the world of wheels show with your splitters on it all weekend.

ProdigyCustoms

01-18-2010, 10:49 AM

Yup. I believe that inside "hump" or "ledge" is more prevalent on the ponchos than for the chebbies IMHO. .

Chevelle and Lemans might as well be Chevy and Ford they are so different. We have 17" 315 drag radials on 10" rims on one of our 67 Chevelle builds on our website and I throw that car arond like I hate it with no rub issues at all. But as you mentioned, there is no "hump" on the Chevelle.

Capown

01-31-2010, 08:39 AM

This is the same issue we have run into on the a-bodies. On Johnny's 67 Tempest, he actually cut out this "hump" on the outer fender above the pinch weld. This allowed us to run a 20x10 with a 275/ wide tire.
I think the most important thing is to measure twice, cut once.

Im still learning all this stuff out on my 67 Lemans is there any way u guys have pics up this inner fender ("hump"Ledge") what and where to cut?:enguard:

ProdigyCustoms

01-31-2010, 09:25 AM

If WMHJR does not have a pic I still have the blue 67 in my shop, I could shoot some pics.

wmhjr

01-31-2010, 10:09 AM

Maybe this will help..
https://static1.pt-content.com/images/pt/2009/03/26March2009gto008-1.jpg

https://static1.pt-content.com/images/pt/2010/01/26March2009gto009-1.jpg

https://static1.pt-content.com/images/pt/2009/04/2April2009GTO003-1.jpg

I don't have any of while the wheelhouse was actually cut. I'll also mention that this allows for some real tight clearances, and I'm only confident because the entire suspension has been rebuilt with stuff that will help to prevent any deflection.