Brake drum wall thickness

[JIPJOBXX]

Ok I know there is a standard for the amount you can take oft a drum for machining purposess but my question and I notice on one of my drums is that its been machined oft center.  So this means the wall thickness is thicker on one side of the drum and of course the other side is thinner.  Just kind of wondering?  And please no sarcastic remarks. Thanks Jon

[Plymouthy Adams]

concusing...why are you still playing with the brakes..thought you reported all was well an in working order...cast could be irregular...but the drum is cut concentric to the hub...consult your repair manual....but....usually .060 max oversize

Edited October 16, 2013 by Plymouthy Adams

[JIPJOBXX]

That would be the inside dia. of the hub I just want to know wall  thinkness of hub.  I thought maybe someone here might just have an answer for that question.  So if you were not to center the hub and machine it than .060" would be the max any place on the hub?

[Dave72dt]

No, what he said was it may have been cast off center but the machining would have been true to the center and that a max of .060 ( common for most drums) may  be ground from the friction surface.  Original diameter + .060 = max diameter.  The max diameter should be stated in your repair manual.  It may be .060. It may be .080.  The manual will tell you.  It will not tell you how thick or thin the drum can be in any one spot.

Edited October 16, 2013 by Dave72dt

[desoto1939]

I have a 39 Desoto and in none of the manuals that I have for this car and any other manuals that I have none of them state what the max can be removed from the drums.  I do know that some of the more modern drums have the amounts cast onthe outside of the drums but the older style usually do not have this information.

 

This is also helpful for my education for my car also.

 

Thnaks for the info

 

Rich Hartung

Desoto1939@aol.com

[Plymouthy Adams]

Rich...while it is not even listed in the specification page on the brakes in the book, Plymouth '46-'54 page 44  , it however referred to in the actual manual within the repair procedures.  Section 4 known as Brake Shoes....there is a caution by ma Mopar that the drums are not to be greater than ,060 on the diameter..that is only .030 metal removal total.  Also over the years of doing brakes most all drums were cast with max diameter values on the drum...

 

AND in the Dodge D19 -D24 the same data is also found within the pages and not on the specification sheet and says no more than .030 metal can be removed for a total of .060 diameter over original size..page 46.  While I do not have a SeSoto book or the Chrysler book here I would not think these same cautions in italicized print or within  a heavy line block in the dodge and Plymouth book would not also be in these.

 

Any shop that does this repair with any regard to safety and personal liability will never turn beyond the factory service limits and they have the charts as supplied for the most part from whoever they bought their turning equipment from..this minimum also holds true for discs...

[desoto1939]

Plymouthy:

 

Thanks for the information.  I have looked several times at my original drums and there is nothing stamped or even cast into the drum with this information.  The older cars like mine did not have this info and I guess  Chrysler felt that the dealership and or the independent garages would have this information in their manuals.  So this is why jopjob was asking because I think from his first post his drums do not have the info.  I have looked around and have never seen as stated value Actually I just looked in my 1935-53 Motors auto repair Manual and in the brakes section thee is nothing mentioned about the cutting of a brake drum and the max that you can take off the drum  I have looked all over and could not find this info

 

Rich Hartung

[James_Douglas]

I am going to relay a conversation I had many years ago.  DO NOT assume it is correct.

 

Many years ago I got the chance to talk with a man that was an engineer at Chrysler.  He stated that he spent most of his working years after WWII in the brake engineering department.  I asked him about drums and oversize.  He stated that when they designed the drums that maximum oversize was cut in 1/2 and then 1/2 again for legal reasons.  So 60 is really 120 with a 100% margin.  Now he advised that that was for a new drum. He told me that he would feel comfortable going to 100 on an old drum that did not have any other obvious issues like heat hard spots and the like. 

 

The above conversation is for historical "oral tradition reasons" and not to be confused as any kind of recommendation.  It is just an account of an interesting conversation.

 

James

[Plymouthy Adams]

Rich...like you I referenced the Motors manual of the period..they are an excellent source of data.  My particular book covers 1940-1955...the turning of the drums is not mentioned at all so therefore I assume the reason for the absence of this data.  I would however like to ask you at this time if you have a Desoto shop manual for your car and if you would take a minute to look for the WARNING within the pages of the brake repair section?  I assure you it can be easily overlooked on a quick scan.  I would find it very strange that this information would not be included.  But again, we have seen some strange things participating on this forum.  Thanks

[TodFitch]

I am going to relay a conversation I had many years ago.  DO NOT assume it is correct.

 

Many years ago I got the chance to talk with a man that was an engineer at Chrysler.  He stated that he spent most of his working years after WWII in the brake engineering department.  I asked him about drums and oversize.  He stated that when they designed the drums that maximum oversize was cut in 1/2 and then 1/2 again for legal reasons.  So 60 is really 120 with a 100% margin.  Now he advised that that was for a new drum. He told me that he would feel comfortable going to 100 on an old drum that did not have any other obvious issues like heat hard spots and the like. 

 

The above conversation is for historical "oral tradition reasons" and not to be confused as any kind of recommendation.  It is just an account of an interesting conversation.

 

James

I guess I should go search for it, but I recall on one of those instructional slide sets on the Imperial web site mention was made of brake linings that were thicker than stock to be used on drums that had been turned up to, if I recall correctly, 0.060".

 

Makes sense to have thicker linings on the shoes so that the outside radius of the lining better matches the inside radius of the drum. But I had never heard about that before (or after) watching that instructional slide set.

[desoto1939]

Rich...like you I referenced the Motors manual of the period..they are an excellent source of data.  My particular book covers 1940-1955...the turning of the drums is not mentioned at all so therefore I assume the reason for the absence of this data.  I would however like to ask you at this time if you have a Desoto shop manual for your car and if you would take a minute to look for the WARNING within the pages of the brake repair section?  I assure you it can be easily overlooked on a quick scan.  I would find it very strange that this information would not be included.  But again, we have seen some strange things participating on this forum.  Thanks

I just looked at the 1938 Desoto shop manual and the 39 Desoto supplemental shop manual that the dealers would have in their shops and there is NOTHING mentioned in either manual in the brake section and or in the Specifications section on the drums and how much can be removed. I have checked these two books several times and nothing is ever stated.

Rich Hartung

[Plymouthy Adams]

Tod...they refer to a set of linings that are .030 thicker than stock lining for use when the drum has been turned to the max .060 diameter...this is necessary due to the very limits of the cam to adjust for wear...cutting to .060 oversize and stock shoes will allow for too much piston travel and complaints from the owner on poor brake performance.  

[Plymouthy Adams]

while thi does not seem to address year specific per Rich's earlier cars..this booklet can be a wealth of information to those here who DO NOT HAVE a shop manual....this is just a cameo clip of one page in the link to point out the very  max tolerance of the drums as per the factory...

while they make reference to the +.030 lining with drums cut oversize..I would take this to read drums that care cut to the max safety limits as listed by the factory at .060 oversize..allowing the cams to be able to adjust the linings to make contact within their limit of travel..

 

http://www.imperialclub.com/Repair/Lit/Master/009/page16.htm

 

 

as a side note here just to tell you that brake shops do have books to go by...my friend took his golf car drums in to be turned..the man measured them, reported that the cleanup would take them outside the manufacturer's stated amount of metal removal for safe operation and therefore did not cut the drums but handed them back saying they can in no manner assume the risk/liability by cutting beyond the set limits..even if used on a golf cart that never is used on a road or street...

Edited October 17, 2013 by Plymouthy Adams

[desoto1939]

I have read that you could use sim stock on the brake linings to make up the difference if the drums have been cut.

Rich Hartung

[_shel_ny]

D19 - D24 manual it is in the area of "brake relining" and labeled IMPORTANT

 

 

D29- D42 manual it is a bit hidden. Just in the text for "service diagnosis".

[Dodgeb4ya]

.030" linings were common practice years ago for use on jobs where the drums were turned close to max oversize. Those oversize linings matched the radius of the oversize drums much better too. If the linings were to be arced to the machined drums less lining material needed to be removed-hence longer lining life.

[James_Douglas]

There is a guy out there that will re-line a brake drum.  It is very expensive.  One thing that really does work to help with heat and fade is to send the drums to CH Topping for the vent holes to be drilled.

 

James

[TodFitch]

There is a guy out there that will re-line a brake drum.  It is very expensive.  . . .

Hi James,

 

Do you have contact information for that guy? Finding good (concentric, unturned) drums for my car is nigh on impossible. I know there are some here that would use that as an immediate reason to swap the rear and put disks on the front, but I'd like options for keeping as stock as possible.

 

Thanks!

[James_Douglas]

Hi James,

 

Do you have contact information for that guy? Finding good (concentric, unturned) drums for my car is nigh on impossible. I know there are some here that would use that as an immediate reason to swap the rear and put disks on the front, but I'd like options for keeping as stock as possible.

 

Thanks!

Here you go:

http://www.jgrelining.com/about.html

 

Best, James

[TodFitch]

Here you go:

http://www.jgrelining.com/about.html

 

Best, James

Thanks!