RE-ARCHING BRAKE SHOES

[jclary]

John Clary
Greer, SC

Life... is what happens as you are making plans.
SDC member since 1975

[DEEPNHOCK]

The term used to bend a shoe to correct it's arc is 'coining'.
They still do it in the remanufacture of the big HD brake shoes.

Arcing shoes to fit a cut drum has become a lost art, as the DOT mandatory spec of x.060" max is pretty strict.
Used to be there was more meat in a drum and when the shoe (with new lining) would not match the arc, they would put overside linings on and 'arc' them to match the drum.
Finding oversize linings, while not impossible, is pretty hard nowadays.

You still see old arcing grinders in the corners of some old shops.
Interesting post....
Jeff[8D]

[klifton1]

I just had this done on the 46 Fxxd brakes on my V8 powered 29 roadster pickup. They work perfect. It was also done on my Speedster. It has drums all the way around.
Klif

55 Speedster
63 Avanti R2
63 Lark R2

[jackb]

Ok... so I think I'm reading this correctly. "Arching" or "coining" a pair of shoes to the drum is re-configuring the metal part of the shoe, not simply turning down the brake shoe material to fit the drum contour ?????

[41 Frank]

I arced brake shoes for three decades as a mechanic, we did it, in house, for vans,trucks and busses and it consisted of grinding the heel and toe of the shoe material until it fit the drum diameter with a few thousands clearance on the ends.This has always been the acceptable way of doing it in the industry.

[jclary]

quote:Originally posted by jackb

Ok... so I think I'm reading this correctly. "Arching" or "coining" a pair of shoes to the drum is re-configuring the metal part of the shoe, not simply turning down the brake shoe material to fit the drum contour ?????

As you can see by the comments, there is more than one way to "skin a cat" so to speak. The method Herbert showed me is a kind of "back yard" method by old school mechanical masters that learned how to make things work with little resources available.Like all of the "tricks of the trade" there is some skill and art involved and those without the mechanical aptitude or ability to sense the nuances, should leave it to the pros. I suspect that when you get to the larger shoes used on big trucks, removing brake shoe material is a more practical option.
You have to realize that we are talking about minuscule changes...large changes would probably indicate a serious problem with either drums cut too much to be safe to use or a poor quality shoe.

John Clary
Greer, SC

Life... is what happens as you are making plans.
SDC member since 1975

[buddymander]

I've cut the rib with a die grinder then clamped the shoe in the drum and tack welded it.

[gordr]

Thanks for posting this, John. A real fine piece of writing, too.

I've used a brake shoe grinder to re-arc shoes, but this is a new one on me. And it makes perfect sense. I'll try it the next time I do a set of drum brakes.

Gord Richmond, within Weasel range of the Alberta Badlands

[rockinhawk]

I was taught to do it the same way as Mr. Boykin. The my teacher said "But they'll wear in after you drive it awhile anyway". So I usually don't bother unless they are really bad.
I met mr. Boykin in the early 80's. My wife and I were driving US1 from south GA. to Baltimore that summer,when she Exclaimed "There's a Studebaker on top of that building!" I really don't remember if it was actually on the building or up on a pole, but it was elevated. We stopped and had a nice visit with Mr. Boykin. Years later I bought a Studebaker with a decal on it with his name as the selling dealer. I thought that was cool. NT


Neil Thornton
Hazlehurst, GA
'57 Silver Hawk
'56 Sky Hawk
'51 2R16 dump truck
Many others.

[BRUCESTUDE]

About 20 years ago the mechanic we had here at the Yakima Fire dept. arched some Stude brake shoes for me; he took a big hammer and tapped the center to "spread" it ever so slightly. He was a Packard shop foreman before becoming the FD mechanic. I since have not tried this, as I am always afraid it may affect the adhesive bond..?

[buddymander]

Re-arcing by grinding severely shortens the life of the shoe. Any shoe that will bend by rapping it against something is also flexible enough to distort that same amount when the brakes are applied, bringing the shoes into full contact with the drum. Light braking will wear out the shoe in the center, just like arcing. By cutting and welding the heavier ribbed shoes, full contact is reached at shorter pedal travel, and shoe life is doubled.

[maxpower1954]

Stan Gundry in his excellent Avanti book "What the shop manual doesn't tell you" describes adjusting the brake shoes by wacking them with a rubber mallet on a hard surface - it worked perfectly on my rear shoes to match the drum on my R-2 GT. I'm a believer! Russ Farris

[buddymander]

If the shoe fits the drum perfectly, then the top and bottom of the shoe will be applied with more pressure, since the shoe is applied uniformly by pushing the ends down thereby bending the middle and applying equal pressure to the center. So I would leave 1/16" or so for bend on the ends.

[maxpower1954]

Didn't think of that buddymander, good you brought that up! Russ Farris