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MochetVelo

Brake Drums Too Tight

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  I got new 3/16" linings installed on the brake shoes of my 1924 Citroen 5HP, and the brake drums are now a very tight fit. One goes on and rotates, but the lining rubs on the drum. The other drum doesn't want to go on at all. The original linings were 5mm thick, I'm told, which is comparable to the 3/16" I had installed. These drums have little wear, so I was wondering if turning them down slightly might be an option. Any pointers?

 

Phil 

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I would not touch the drums. Use 80 to 150 grit abrasive roll (https://www.woodworkingshop.com/abrasive-rolls/) going back and forth like polishing a shoe to take down the 3/16 to fit. This would take down the new material as evenly as possible and not leave any high spots . Obviously wear protection while doing this.

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There is a tool called a Breke Doktor that is made just for your problem. They are difficult to find. Your going to have to somehow grind/cut the material down. If you do it by hand it won’t be flat and the surface area will not be in full contact. Dust is an obvious issue.

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I would not turn the drums to accommodate new linings. Change to thinner linings. Save all the drum surface you can. For a 1924 they were probably woven linings. No? Are the brake drums stamped steel or cast iron?

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Thanks for those tips! I'll refrain from turning the drums. For some reason, I didn't think of removing shims that were installed over the cams. They must have been used to used when the linings were worn or thinner. This seems to be the trick.

 

Phil

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The drums now slide over the shoes, but they do rub slightly when turned by hand (no wheels installed as yet). I assume the linings will conform somewhat during operation, but wonder how much rubbing is too much.

 

Phil

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23 minutes ago, MochetVelo said:

The drums now slide over the shoes, but they do rub slightly when turned by hand (no wheels installed as yet). I assume the linings will conform somewhat during operation, but wonder how much rubbing is too much.

 

Phil

A very slight rubbing of the shoes should be good. You do not want much travel in them.

Edited by keiser31 (see edit history)
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You may want to take the shoes and lay them inside a drum - often the shoe diameter does not fit the drum diameter (I hear old timers calling it "arc") -  You may have to touch up the tips of the shoes via using such as a belt grinder (and Ed is correct there is a specific machine for this).  One of the reasons people complain about old cars not stopping is because they miss this step or use too modern of a lining (this is a case where old primative works better than new tech).  And dust is not something you want to inhale. 

 

Also, If I told you some of the bills I have paid to have new brake drums machined you would never want to ever turn a shoe and loose any meat off the metal.  

 

An interesting story - We were at the Franklin meet one year and a fellow was complaining that all he had to do was touch his brake pedal and his car came to the end all be all screeching stop (which I usually do not mind, though this was in the we are all going to die way) - turns out someone had ground the drums so thin that you could actually watch the drums deform upon brake pressure - after taking a hub apart for  more close  look everyone said too dangerous and nobody would let him drive his car the res of the meet.  Good news was he was in the right place for the discussion and was not too hard to secure parts (another 25 years later though he parts supply is even worse though - to the point of drums having to be reproduced).  

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I arc my shoes to each drum with this Ammco arcing machine...

Arching_mopar_shoe_to_fit_drum_Large_.jpg

Brake Shoe Thickness and Non Conformity Tech.JPG

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