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Old 07-29-2020, 03:07 PM   #1
CA Victoria
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Default Oversized Brake Drums

I am working on putting together a set of 1935 Ford mechanical brakes & drums.
There are two different camps when the topic of brake drums comes up.
The warning comes to not use brake drums if turned beyond 12.060 stating it is dangerous. Why?
The folks who have worked on these for years will cite using drums turned well beyond 12.060, none so far can remember a drum failing?

The drums I have turned to 12.100 have about .110 wall thickness.
So is the warning because of drums failing, or overheating, or warping?

Several shoes I have removed have paper like shim material under the lining to compensate for the drum diameter. I have not found thicker woven lining so I have made .030 metal shims to use with woven linings.

Lots more experience here on The Barn than I have.......so do you see any pitfalls with using oversized drums with shimmed linings?
Any one with experience of drums failing?

Thank you!
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Old 07-29-2020, 04:03 PM   #2
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Default Re: Oversized Brake Drums

Get involved in an accident even if brakes weren't an issue, having drums in excess of the maximum is looking for a lawsuit. JMHO.
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Old 07-29-2020, 04:07 PM   #3
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Default Re: Oversized Brake Drums

Overheating and brake fade as in no brakes.
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Old 07-29-2020, 05:18 PM   #4
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Default Re: Oversized Brake Drums

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Get involved in an accident even if brakes weren't an issue, having drums in excess of the maximum is looking for a lawsuit. JMHO.
Never have I heard of anyone ever having someone wanting to measure brake drums for being overturned after an accident.
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Old 07-29-2020, 05:55 PM   #5
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Default Re: Oversized Brake Drums

I’m stuck on the application of a .060 limit to every drum ever made....
How thick are your brake drums after turning?
What is your experience?

Quote from another........
“Most drums are cast with enough thickness to allow 0.090" of wear. In other words, the difference between a drum's diameter when new and its discard diameter is 0.090," but that doesn't mean you can machine a drum right up to the 0.090" limit.
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Old 07-29-2020, 06:37 PM   #6
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Default Re: Oversized Brake Drums

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most machine shops won't turn beyond .060.
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Old 07-29-2020, 06:52 PM   #7
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Default Re: Oversized Brake Drums

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Never have I heard of anyone ever having someone wanting to measure brake drums for being overturned after an accident.
I spent almost 8 years as an investigator for the California Department of Transportation's Legal Division. The last 2 1/2 years as the supervising investigator in charge of all law suit investigations pertaining to vehicle (and other) accidents. It does happen. The California Highway Patrol Multi Disciplinary Accident Investigation Team (MAIT) conducts lengthy accident reviews which focus on all factors that may have contributed to the cause of an accident, including brakes.
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Old 07-29-2020, 06:54 PM   #8
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Default Re: Oversized Brake Drums

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most machine shops won't turn beyond .060.



.only because it's ILLEGAL! You kill some baby with that 'old hot rod' and the Momma gets the 'right' attorney involved, they will tear that car apart looking for anomalies, and they'll make the remainder of your life unbearable! DD
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Old 07-29-2020, 06:56 PM   #9
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Default Re: Oversized Brake Drums

just be careful if youre oversize , you'll need oversize linings to match, dont just buy off the shelf and expect them to work.
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Old 07-29-2020, 06:58 PM   #10
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Default Re: Oversized Brake Drums

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Never have I heard of anyone ever having someone wanting to measure brake drums for being overturned after an accident.
It depends if there was a fatality or major injuries. The police may do it in the case of a fatality or the insurance investigator may do it when there is a law suit.
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Old 07-29-2020, 07:01 PM   #11
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Default Re: Oversized Brake Drums

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It depends if there was a fatality or major injuries. The police may do it in the case of a fatality or the insurance investigator may do it when there is a law suit.

That makes it simple. Just don't get involved in a FATAL accident, and just refuse to let anybody file suit against you! DD
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Old 07-29-2020, 07:10 PM   #12
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Default Re: Oversized Brake Drums

Doesn't even need to be an at fault accident. My son was T boned by a car that ran a stop sign (totalled a fresh restoration of my old 56 Chev pickup) 100% fault of the person who hit him. He was not injured thankfully but even so, the truck was taken to a shop and all 4 brakes were checked and measured. I kept a log of everything done on the truck and that was in the glove box, and everything I claimed I did was checked off as in good condition. If anything was off the insurance company of the person who hit him would not have paid anything and fought it in court. It is what they do, insurance companies have lawyers to do that and the average joe can't compete meaning afford to fight. They (after a year) settled for 30k but they strung it way out on something that was cut and dried, police issued a citation and everything.. It is false economy to use safety issue parts (steering, brakes, tires) that are not legal.
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Old 07-29-2020, 07:53 PM   #13
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Default Re: Oversized Brake Drums

Some folks worry more that me. My wife was a fatality in a car accident. I followed her car from tow yard to junk yard, to junk yard, to a 'final' junk yard. I can assure anyone, that NO ONE ever came to inspect ANY portion of her car. And, I saw at least two things that I feel were manufacturers defects, that made her accident a fatal one. No one cared. And the insurance company paid promptly. My point being, some of the above posts present possibilities. But, seems to me, very unlikely. New or newer cars, yes, I wouldn't cut corners on drums or rotors. They are mostly inadequate when new, anyway. The shittiest brakes I've ever encountered, have been on modern, near new cars. I live in the mountains, and I've had at least two modern cars where I could warp the rotors on just ONE trip off the hill. But, for our 'old' cars, seems to me there is, and always was, a little extra margin. Obviously, opinion. And, goes without saying, I can predict opposing opinions.
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Old 07-29-2020, 09:17 PM   #14
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Default Re: Oversized Brake Drums

It seems odd to me that anyone would want to deliberately build a vehicle in violation of the law. This type of stuff is what leads to government inspections to the level of being ridiculous. There are legal limits on how much you can turn a brake drum. If I remember correctly there are drums that can be legally turned beyond .060, but these drums are clearly marked as such.

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Old 07-29-2020, 09:31 PM   #15
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Default Re: Oversized Brake Drums

Quote:
Originally Posted by 51504bat View Post
I spent almost 8 years as an investigator for the California Department of Transportation's Legal Division. The last 2 1/2 years as the supervising investigator in charge of all law suit investigations pertaining to vehicle (and other) accidents. It does happen. The California Highway Patrol Multi Disciplinary Accident Investigation Team (MAIT) conducts lengthy accident reviews which focus on all factors that may have contributed to the cause of an accident, including brakes.


California, that just explained it. 🙂
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Old 07-30-2020, 12:56 AM   #16
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Default Re: Oversized Brake Drums

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Originally Posted by JSeery View Post
It seems odd to me that anyone would want to deliberately build a vehicle in violation of the law. This type of stuff is what leads to government inspections to the level of being ridiculous. There are legal limits on how much you can turn a brake drum. If I remember correctly there are drums that can be legally turned beyond .060, but these drums are clearly marked as such.
Doing shoddy work that can be called out after an accident will also give our hobby a black eye. It might also lead to targeted regulations.

Last edited by J Franklin; 07-30-2020 at 01:01 AM.
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Old 07-30-2020, 02:06 AM   #17
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Default Re: Oversized Brake Drums

Sometimes it feels good to live in Sweden. No problems with lawsuits :-)
Just wondering where does the 0,60 figure come from?
Is it something Ford said.
Or is it just a safe number that all cars have to use?

Don't know much about drums, but disc's you use the number the manufacturer say.
And its usually "stamped" on the disc.
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Old 07-30-2020, 06:33 AM   #18
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Default Re: Oversized Brake Drums

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Sometimes it feels good to live in Sweden. No problems with lawsuits :-)
Just wondering where does the 0,60 figure come from?
Is it something Ford said.
Or is it just a safe number that all cars have to use?

Don't know much about drums, but disc's you use the number the manufacturer say.
And its usually "stamped" on the disc.
If you have an opportunity, take a look at a '40 drum that has been turned past .060. I have some that, according to my drum mic, are .090, .100, one is even .120. These came off old brakes systems.

Even at .090, the metal band is visibly thinner. Why does that matter? A thin drum will heat up much quicker and starts to distort causing brake fade.

My thoughts are, cut corners somewhere else. Brakes are crucial for you and everyone else on the road with you.

Interesting note, the ribs casts into Lincoln and '42-'48 drums are to strengthen the drum outer "band" and to help aid in cooling like at air cooled motor.
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Old 07-30-2020, 07:20 AM   #19
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Default Re: Oversized Brake Drums

you could have the drums banded.i seen it done on model a drums
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Old 07-30-2020, 07:29 AM   #20
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Default Re: Oversized Brake Drums

Mr 42,
I could not find the reference and hence asked the same question here. I am not dodging safety just looking for the “why is it”. & what have you done to mitigate the differences. Maybe with 51504bat’s experience with Ca Highway Patrols MAIT team he can provide more info.
I am venturing to guess there are at least a gaggle of early Ford’s with original mechanical brakes and hopefully most have been done safely and stop well. So far no one has offered up any new drums for 32-38 Fords. Agreeing with Tim on drum safety the standard is based on manufactures design and at least with modern drums it is stated for the service person.
Sooooo with out info from Ford/Kelsey Hayes it is fair to ask what is the minimum thickness for a 1935 Ford Drum. At 12.090 the ( “stated maximum” ) drums are about .125 thick.......

So far I have restored the brake assemblies with NOS Ford parts, if you have 2 NOS 1935 drums I’d love to buy them!
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