# 1968 GTO rims with brake options?



## Pstamato (Aug 18, 2014)

Hello I am wondering if anyone knows the correct markings for a 1968 GTO with Disc brake wheel/rim applied to the rim? I believe they are JA but I am not entirely sure.

Also with the correct 68 rims for Disc brakes, what size disc can you fit?

Thanks all!


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## rlslavik (Jun 21, 2014)

Not sure about the markings but I do know there is a difference between rims for 4 piston calipers and single piston. 
My car originally had the 4 piston calipers on the front.
The Rallys rubbed (grinded) when it was delivered.
Undriveable.
After realizing the 4 piston calipers would cost $600 EACH to have them shipped off and rebuilt (no other option I could find at that time) I decided to swap them out for single piston calipers standard to most A body GMs in those years.
With single piston calipers there was adaquate clearance and no more rubbing.

So if you have 4 piston calipers, not just ANY Rally will work.
They are much more specific and require more spacing on the wheel.


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## Squidtone (Nov 26, 2010)

Hello,
Yes, if the 68 GTO came with front disc brakes, they were 4 piston fixed calipers (two pistons inboard, two pistons outboard.) 

For the A body cars that year, only two Rally II wheel (codes) were used, and they were both 14 x 6 wheels.

If it was drum brake all around, they got the "JC" code wheel. 
If it was a disc brake car, it got the "JA" wheels. The "JA" wheel has a slightly deeper offset, so it shows less rim ("wheel hoop") on the outside (on the order of 0.375")

Confusingly, both the JA and JC wheels will fit with no problem on a 4 piston caliper disc brake car. In fact Firebirds of the same year used JC wheels even if it had discs.

These two early Rally II wheels used a unique center section that had deeper lug nut "pockets" so that the center stood out further from the hub/caliper in order to clear the fat calipers. (there are a couple other code Rally II wheels from that era that also used this unique center section) By 1969, Pontiac used the single piston calipers, and by '70 or '71,the Rally II wheels center sections were changed to a shallower lug nut pocket. So typically, later year Rally II wheels won't fit on a 67-68 disc brake car. 

If JA wheels are too hard to find, use the JC wheels. 

Good luck!
dave


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## Pstamato (Aug 18, 2014)

Thank you so much for the info!

My car is drum all around but I was going to convert it to disc. I like the original rims but now I'm thinking of going 1970 pontiac rally II 15x10 wheels. However to your point now I'm worried they won't fit.

Was it only disc brake cars from 68 that wouldn't fit later rims or both drum and disc?


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## Squidtone (Nov 26, 2010)

Yes, if you've got all drums now, just about any Rally II wheel will fit onto the car (of course as long as the wheels are not the "big car" big bolt pattern)

If you're converting to disc brakes up front, you have a ton of choices for brakes. On one extreme you could find all original '68 hardware and bolt it on (4 piston fixed caliper style) but this might actually be kind of hard to find since I think these brakes only came on a minority of cars in that year.

Or, you could go with an early 70's A body brake set up which uses the ubiquitous floating single piston caliper. these parts are still very easily obtainable from tons of suppliers. And it's all GM design.

Or, you could go with aftermarket set ups that use the fancy multi-piston calipers that are polished and look great.

If you go with the A body size GM single piston brakes, just about any Rally II will fit. (except of course the big bolt pattern "big car" Rally II wheels)


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## sixtysix (Jul 2, 2010)

what rim was the JK marking used on


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