Technical Buick Drum Dimples!?!

Hey Happy Thanksgiving folks! Just in case somebody was taking a break from the Turkey for a little HAMB, I figured I'd post my latest quandary...

I just scored (at least I hope it's a score) these 45-fin alloy Buick drums, and the liner is full of little dimples. I was told these drums came off of a 1963, and when I searched I saw a thread that talked about how Buick only dimpled the drum liners in 1958, so is there something different going on here...? Have these maybe been re-lined??? And irregardless, will I still be able to have them turned?



Thanks! Hope everyone has a warm and safe holiday.

 

Probably off a '58 if the dimple story is true. They should be able to be turned, the inner diameter is probably a bigger concern, wether or not there is enough material left to turn and still be within spec.

 

Are the dimples to show wear limit?

 

'63 would have had tapper roller bearing. Ball bearing use was way earlier. I thought the liners had holes in the back sides and the drums were cast around them so they were "keyed in" for lack of better words. What is the ID of the drum lining measure now? 12.090 is MAX

 

Nope the dimples are to let it gas out better. less fade. I would imagine that it is a one year thing because of cost and minimal return.

Wouldn't matter what year the drums are as long as they work, they didn't change them much.

 

I think the ball bearings are the big clue. As mentioned, by 1963 they would have been using roller bearings.

 

I seem to remember reading the dimples were a first year thing. And, what year did they switch from 45 to 90 fin?

 

You need to check the diameter.They look thin to me.

 

The style of bearing shouldn't be an issue. Everyone I know including myself used Ford spindles/hubs for an easy fit to our beam axles. A bit of machine work by a competent machinist, and you are on the road.

 

The dimples were part of the manufacturing process. They perforated the steel liner then cast the aluminum around it. The aluminum flowed into the holes and locked the aluminum permanently to the steel. Otherwise it is hard to keep them together because aluminum expands at a different rate than steel. I don't know if they ever did them any other way.

You will need to look up the factory spec for turning the drums. It will say something like maximum oversize .080 or whatever. Measure the drum, if it is supposed to be 11 inches but is 11 inches + .080 it has already been turned the max.

 

The linings start out about the same thickness as the aluminum lip.
The aluminum lip is cut all the way back when using 39-48 backing plates with the 42-48 hubs but the liner must not be cut.
The real killer is corrosion between the iron liner and the aluminum detectable by a white crust sticking out. Yours look fine.
I have machined more sets than I can count.

 

These are way over-turned. The dimples are to lock the Iron liner to the alloy drum. The drum is cast over the liner.

Measure them. As has been mentioned 12.090" is the max. I am willing to wager that you are far beyond that.

Also, ball bearings.

 

Learned something today.

 

I have a set like that in my garage that are now only good for decoration. It's what Rusty O' Toole said. I had them on my car and when you apply the brakes they make a grinding sound because the aluminum grinds out and gets between the shoe and the drum. Turned out too far.

 

So they ARE 63 drums, but the smooth liner is turned straight through into the casting? Jeeze! No wonder the seller wouldn't give me the dimensions. He probably knew they were trash. I just figured they were the 1958 Drums...

 

I thought the early drums were the 45 fin and the newer ones were 90 fin? You will need the factory spec and measure the drums, if anyone still has the old brake drum lathe they should have a caliper for this purpose. And a hand book of sizes.

 

Rusty,

90 fins came out in 66 or 67. 58's had dimples in the liner (one year only), but I'm figuring from the comments that THIS is not what the dimples look like. Sure would be nice if somebody could say absolutely 100% one way or the other. I'm not very good at judging thousandths of an inch in a low res photo.

The price on these was right (if they're serviceable), but the guy is either a scammer or inept, because he can't figure out how to measure them...

 

Burn an inch on a regular tape measure, 12 1/16 is 12.060 or basicly half the life gone. 12 3/32 would be 12.093 and unsafe to run.

 

If they are turned too far out here is a company that can fix that. They reline the drums.
http://www.jgrelining.com/

 

The information I have seen indicates that the pre '59 drums had the retaining holes in the iron liner and it was normal to see the aluminum "pegs".
The later drums had radial grooves and ears on the iron liners for retention. The grooves are visible and the arrows point out the ears in the attached picture of a drum (the piece to the right is the iron liner reversed). Also a good illustration of the "white death" these drums can develop.
Don't condemn them, before you get them measured with a drum mic; but remember if you adapt these to Ford hubs, they will need another turning to true them.

 

If the aluminum in the dimples can touch the friction surface of the shoes, it will foul them instantly.

 

Not sure how that aspect worked out; but here is a copy of a GM picture noting the the change in drum construction. Found that a while back while I was looking into those drums. It was in one of those little booklets Hot Rod put out in the early sixties.

 

Has anybody here ever had them reline a set? What's the cost like?

Thanks Rich,

That was exactly what I was after. Man, this is bumming me out. The drums were priced fair, but the guy can't be talked into measuring them...internet deal, so I can't measure then myself...

 

If he would not measure them, that would be a deal breaker for me.

 

I think the 90 fin is post '66 but don't hold me to that. I have a pair of NOS 90 fins that I am setting up for rears with a 9". I figure that mine are for stopping not for looking at and leave the 45s for the guys that need them out in the breeze.

Nope just did some research via the web and a Chiltons and the 90 fins it appears to be a '65-'71 thing. So post '66 would not be correct.

 

As above...don't buy them if the owner won't measure them. 12.075 is the largest finished size that I would accept. I paid 200.00 for mine (10 years ago) and they were both < 12.040