1962 Brake Drums
I measured my 4 drums and they all measured 281 mm......when I took them to two parts stores that had old time guys and lathes, they said they would not turn them, that they were right at spec and could not remove more material, they both had Chinese made replacements that measured new at 279 mm....as I looked at them with a quizzical face they both said sorry? Could I have your input on these drums? What would you do? Thanks....Dino
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Dino Lanno -
Re: 1962 Brake Drums
Dino, try another place that turns drums.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight. -
Re: 1962 Brake Drums
The nominal diameter is 11". Later replacment drums have "max. dia. 11.090" stamped or molded into the casting based on a FMVSS that went into effect in 1968.
11.090" (25.4) = 281.7 mm, so they do appear to be effectively at the limit.
New drums should be right at about 11.00" or 279.4 mm.
A good approximation to remember is that 1 mm is about .040"
I don't know where drums are currently manufactured, but buy "name brand" like Bendix, Wagner, EIS, etc., however, all may come from the same offshore source.
DukeComment
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Re: 1962 Brake Drums
OEM drums usually have a max dia groove already machined next to the inside face of the drum. As long as you can still hang a fingernail in the groove, you can turn them until the groove is gone. Unless the drums are really bad, just use them as is. Shoes are cheap and you will probably never wear out another set anyway. Think of it this way... after your shoes wear in, all those tiny grooves add surface area to maximize your stopping potential...
Comment
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Re: 1962 Brake Drums
When the drums are on the higher side of the tolerance which was 11.090 you can have the shoes arched to fit the drum. Most replacement shoes come arched for a .030 oversize drum.Comment
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Re: 1962 Brake Drums
I remember looking in to this a few years back. I believe I found the maximum dimension for turning brake drums in the 1961 full car Chevy shop manual. I don't have the manual with me, but if I remember correctly the manual indicated not to turn the drums down more then .060".
DennisComment
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Re: 1962 Brake Drums
EXACTLY! I've been telling people this for years. I think that we've been brainwashed into thinking that drums always have to have a smooth machined surface. This is an engineering spec that doesn't prove any appreciable difference in most applications. If the drums are not out of round and the grooves are not deep, there is no reason to turn them. This goes for rotors, too.OEM drums usually have a max dia groove already machined next to the inside face of the drum. As long as you can still hang a fingernail in the groove, you can turn them until the groove is gone. Unless the drums are really bad, just use them as is. Shoes are cheap and you will probably never wear out another set anyway. Think of it this way... after your shoes wear in, all those tiny grooves add surface area to maximize your stopping potential...Comment
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Re: 1962 Brake Drums
Back in 2007, I went through the exercise of changing out my complete brake system (with the exception of the long steel brake lines which were changed out in the 90's). My car is a 63, so there are some differences between it and a 62. Mine had the sintered metallic linings which were coming apart with the metallic pads rusting off of the shoes and floating in the drums.
In the process, I automatically calculated that I should replace the drums as I expected them to be worn more than if I had standard brakes. I bought an entire set of drums from a local Corvette parts vendor. To begin with; the replacement drums had no grooves for the anti-chatter springs (which I also had some new ones in my plan). They also did not have the knock outs for adjustment of the star wheel adjusters. And therein was part of my problem; I could not get them to adjust right. I finally determined that the replacement drums had a slightly different offset than the originals, i.e. the drums would not fit back against (near) the backing plates so the linings would not engage the friction surface within the drum properly.
I then had to have a local "Just Brakes" shop turn my original drums a slight amount to true them up (they were all within spec, the worst one trued to 11.032").
Bottom line is that one should check any new drums carefully. They are probably generic, but they won't fit Corvettes.
Stu FoxComment
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Re: 1962 Brake Drums
Tracy & Paul,
You are right on, I do the same. Sometimes it's a little more work removing the drums when they are groved but a few taps and pressure and their off.
There was a court case that brought all this on. The person said that their brakes failed causing the accident, so the lawyer put the shop owner on the stand. He asked the owner to answer yes or no. His question was, " would turning the drums make a better job"? Would new cylinders have made the job better? And so on. He accused the shop owner of cutting corners and not doing good work. Lawyer won the case. After that, back in the 60's, major shops only did the whole thing. Most went out of business because people only wanted to pay for what was needed, not the whole thing.
DomComment
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Re: 1962 Brake Drums
Dino------
I agree with the others; you can likely use the drums you have without having them machined. However, if you do decide you need new drums, I'd go with Delco #18B382A, aka GM #19241897. These are OEM or near-OEM quality drums. I don't know where they are made.In Appreciation of John HinckleyComment
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Re: 1962 Brake Drums
Thank you everyone for your input and ideas.....very much appreciated! I plan to use my original drums, they have no grooves and appear to be turned with very little wear. They are at the max though.... I suspect the car had a brake job prior to pushing it in a barn....pads were like new as well. DinoDino LannoComment
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