[Geoff]

I am hoping somebody might have a parts book that can answer my question.

My GTO came with the aluminium front drums. The mounting face [ where it mounts to the hub ] is much thicker than the steel drums. If the same hub was used for steel & alum drums, the front wheel track would be about 1/2" [ or more ] wider than a steel drum car. Yet only one dimension is ever quoted for the wheel track.

If anybody has a parts book, I would be interested to know if different hubs were used.
Thanks.

[Kenth]

According to the 1967 MPC the 1966 GTO uses either,

1. 9785109 HUB & DRUM steel - w/radial fins- exc.metallic brake lining.

2. 9785375 HUB & DRUM w/metallic brake lining - white paint on fins.

3. 9781513 HUB & DRUM w/aluminium brake drum.

No separate drums or hubs were sold at the time.

To retain track dimension w/alu drums i guess the hubs on the assembled units had different offsets?

[Geoff]

Kenth,
Thanks for the info.

[Scarebird]

Originally Posted by Kenth

...To retain track dimension w/alu drums I guess the hubs on the assembled units had different offsets?

Not impossible but I would find it unlikely. The hubs then were forgings and so expensive to make, along with the fact that the backing plates would also need to be different.

My guess is that they just did not bother with correcting the track info.

[Kenth]

Before we have measured the dimensions of the aluminum drums and hubs, there is no evidence that the backing plates are special for the aluminum drums.

[60sstuff]

FWIW,
I have several sets of Original 65-66 Aluminum drums, plus a set of Red ones on my ‘66 Rally I GTO.

Over the decades I have used these Aluminum drums on other 65 / 66 GTO’s with no issues.
They match up to the backing plates just as the cast iron drums do.

I took some photos and measurements of a ‘66 Aluminum drum next to a ‘66 Cast Iron drum (both having their factory Red paint) and they are within an 1/8’’ difference.

[Geoff]

Are you interested in selling a pair of drums?

[Kenth]

Looks like the hubs are the same for iron or alu drums, and that the alu drums will alter the wheel track some. (Widetrack).