Mechanics brain needed
Race Director
Joined: Aug 2004
Posts: 15,329
Likes: 2,271
From: NorCal
Great news. What happened was, the original drums were cut oversize to clean them up. This is normal procedure. What didn't happen is the shoes getting arced to the new drum oversize. Shoes are not arced anymore, so you would need to drive thousands of miles for them to wear into the new drum oversize. Or, you can 'hammer arc' the shoes by standing them on their ends with the lining facing up and smacking the center of the lining with a hammer to slightly flatten the curve of the shoe. I have done this more than once, and it works. You need to be careful, though.
Not sure I understand “standing them on their end” Does that mean on one end of the shoe with the shoe being vertical and hammer on the other end so as to strike only on steel? That would seem to increase the arc.
Or, more logically, when you say “hammer in the center of the lining” that sounds more like resting the shoe on it’s back (inner side) with the shoe being horizontal and hammering directly on the lining material. That would decrease the arc.
How do you protect the lining material from being damaged by hammering on it? Wouldn’t a direct hit from a steel hammer dent, chip, or maybe even shatter the lining?
Does this work for both riveted and bonded linings?
I am confused by this process. Thanks for clarifying!
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,461
From: Fresno California
Yes, you got it on the third paragraph. Put the shoe on a workbench or on the ground and hold it so the lining is pointing at the sky with bot toes of the shoe contacting the ground. Take a plastic or wooden mallet, and whack the center of the shoe hard. I have done it with a regular big ball peen hammer. If you have some old shoes lying around, try it. Due to the construction of the shoe backing, it will not bend much at all, but a few thousandths, which will give you full contact on a drum cut .030"-.050" oversize. Works on riveted and bonded shoes. Disclaimer: I have not done this within the past 10 years on new, non-asbestos based shoes! The linings on both my GTO's are over 35 years old and asbestos based, and the last time I did this was probably in the '90's. But I have done it a few times and it works. Learned it from an 'old timer' in the early '80's when arcing by grinder was going away.
Back when I started out, I did a lot of brakes on early '60's Caddys and Buicks which had huge brake drums all around, and these cars would pull right or left if the shoes were even slightly off.
Back when I started out, I did a lot of brakes on early '60's Caddys and Buicks which had huge brake drums all around, and these cars would pull right or left if the shoes were even slightly off.
