1963 GM Advertisment - Aluminum Brake Drums

[Rick G.]

The current issue of Vette Vues has a reproduction of a two page advertisement from 1963 on pages 64 & 65 which list the available options for the new 1963 model to include "monstrous finned aluminum brake drums with metallic linings". Does anyone know if GM seriously experimented with aluminum drums on the production corvettes or was this just part of marketing?

Thanks in advance,

Rick

[John H.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

The current issue of Vette Vues has a reproduction of a two page advertisement from 1963 on pages 64 & 65 which list the available options for the new 1963 model to include "monstrous finned aluminum brake drums with metallic linings". Does anyone know if GM seriously experimented with aluminum drums on the production corvettes or was this just part of marketing?

Thanks in advance,

Rick

Rick -

I saw that too - just an ad agency copy-writer's mistake; he must have been thinking about (or looking at) a big Buick. Buick was GM's "lead division" for Brakes, and did most of the work on drum brake engineering.

[Duke W.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

Pontiac also had an aluminum fiinned drum option, and it may have been standard on the Grand Prix.

What you saw as the "wheel" was mostly the finned aluminum drum. The actual wheel, which had a rather small spider was bolted to the OD of the aluminum drum and the hub flange with IIRC 8 lug nuts.

The drum was cast and I believe an iron "ring" was installed in the mold. As the liquid aluminum cooled and solidified, it contracted onto the cast iron ring that was the friction surface. Then the casting was machined, and I believe these drums required a special hub of large diameter that had a provision for the 8 lug nuts on a large circle.

Duke

[Terry M.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

Ever try to change a tire on those Pontiac wheels? And you think the IRS on Corvettes can present service issues? We don't know how good we have it.

[Tom P.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

In later years (early 70s), the Buick A-body cars (Regal series) was available with finned alum drums. The hub was a direct bolt-on swap for other GM A-body cars (such as the Chevelle). My 70 Chevelle is a factory pwr drum brake car. Of course, there is NO question that disc brakes are better than drums, but one day I was given a pair of Buick Regal alum front drums/hubs. I checked to see if they would fit the Chevelle. Sure enough, they fit perfect. I seriously doubt that the alum drums have better stopping ability than iron drums, but they certainly will dissipate the heat better. As mentioned above, they have an iron brake ring with the alum cast around the iron ring.
Yes, I COULD convert the Chevelle to discs, but for my kind of driving, the pwr drums work fine and the alum drums look great!

[Jim L.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

The drum was cast and I believe an iron "ring" was installed in the mold. As the liquid aluminum cooled and solidified, it contracted onto the cast iron ring that was the friction surface.

It's easy to visualize the aluminum growing at a faster rate than the iron as the brakes heat up and, therefore, losing its grip on the iron ring. What would have been done to compensate for this possibility?

[John H.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

We had Aluminum rear brake drums on a full size Chevy in the late '80's

[Duke W.]

Re: 1963 GM Advertisment - Aluminum Brake Drums

You may know from racing that it's not a good idea on a drum brake car to pull on the parking brake in the paddock when you return from a track session. As the drum cools down and shrinks, it may be difficult to release the parking brake then next time you go out. I always left the gearbox in first and choked a wheel.

Drum expansion will result in more pedal travel under severe braking conditions when the drums are at maximum operating temperature. In such cases there is likely to be large temperature gradient between the cast iron friction ring and the aluminum drum, which tends to offset aluminum's greater thermal expansion.

Aluminum is lighter than cast iron, has lower thermal resistance, but less heat capacity - characteristics that tend to offset, which is probably why aluminum drums were never widely used, but they were a great "gee whiz" feature back in the drum brake days.

Duke