Brake shoe fitment

[Ron Gusack]

I remember people talking about making their shoes fit their drums better, but I never knew how they did it. I have a drag car with drums all around and I have a hard time keeping the car from creeping out of the beams. I can see that only a small part of the shoe is making contact with the drum. The middle of the shoe arc makes contact and tapers to no contact at each end. I'm searching for a pair of pressure gauges to see what's going there, but haven't found a highly recommended pair yet. I know it's a lost art, but any ideas on fitting these shoes better?

[SupStk]

It used to be brake shoes were ground to fit the drums. The brake shoes were clamped in the machine, the arch was set to match the drum and a big sanding roll would remove brake lining from the high spot.

Gauges, I don’t know what you are asking about. Hydraulic pressure gauge?

[modok]

Do you want to do this by hand, with disk sander, with a lathe?
Or do you want to buy the shoe arcing machine?
I have one for sale

[Ron Gusack]

Do you want to do this by hand, with disk sander, with a lathe?
Or do you want to buy the shoe arcing machine?
I have one for sale

I was thinking of doing it carefully by hand with a belt sander. Your machine is probably too expensive for my one time use.

[modok]

Yeah, I just to threaten people with that horrible old contraption.
By disk sander i meant the woodworking type with a table on it so it stays square. I have a 12" one. There are also large belt sanders that can function the same.
You can get pretty close this way.

It is preferable to have contact in the middle to start, meaning the radius of the shoe should be smaller than the drum, but just slightly.

[ijames]

The shade-tree method I was told (but never tried) back in the mid-70's was to glue a sheet of coarse sandpaper to the inside of the drum with rubber cement, put it all together with tire for a handle, and spin the drum while slowly adjusting the shoes tighter and tighter. I'm sure somewhere there was a "hold my beer" moment when the car was started and put in gear . I was a teen at the time, and have no idea if this actually worked or not, but if you are looking for cheap .

[hoodeng]

For a once off a reputable brake service center will fulfill your requirements to the best outcome. A couple of things.

For no or little warmup a brake material like 'Kuhne Multibrake 3915" is the go to lining.

When presenting your drums and shoes for matching take the backing plates with them so the machinist can not just adjust the radius of the shoe but the orientation of the shoe in relation to the drum. At this time they will also check when instructed the true and alignment of all contributing components.
After service and reinstall look for a company that has a rolling road that will read brake force balance between all wheels.

I have done it this way for a number of restorations that have twin leading shoe orientation, the difference is chalk and cheese.

These are your brakes after all, better than what you will ever need is the minimum requirement.

Cheers.

[Sir Yun]

additional :
if is manual adjustment try setting them full tight, then using a big rubber mallet to whack it like you mean it all around then it generally is lose again. Repeat for a few rounds.There should be enough braking pressure to get a decent contact unless it is a mile off once everything is settled.

ymmv

[FC-Pilot]

As far as shaping the shoes, I would say any of those should work. One thing I recommend is getting the brakes warm. Generally cold brakes are not as effective as warm brakes. As bad as it sounds you may want to drag your brakes pulling through the lanes and before hitting the water box. You don’t need them boiling, but ice cold brakes just lack effectiveness. I bet they come around enough to hold you on the line if they were holding before.

As mentioned by Hoodeng, there are compounds that do work ok cold. What compound are you using?

Paul

[Ron Gusack]

Thank you all for the ideas. I'm using Bendix shoes with AE4280-EE 10 on the side of the lining. I bought 2 sets and installed primary shoes on all 4 corners. It vibrated really bad when stopping so I went to the Class Racer forum and was told not to run 2 primary shoes in the front. I pulled one off each front and it's been fine. In the 70's we ran metallic shoes and they improved stopping distance a ton, but that was a clutch car so no starting line issue. I was going to cut a piece of sheet metal to the drum ID size to use as a gauge to help identify the high spots on shoes.

[Dan Timberlake]

I'm probably overthinking it, but I believe brakes shoes are pretty flexible.

The patterns left after a few hard stops might be a worth consulting when hand fitting.

[Ron Gusack]

How bad is the mess when using a machine sander or an endmill? I've got a mill/drill and a rotary vice that I'd need to make a fixture to hold the shoe, but I think I could mill or sand an arc. I'd have to do it in my basement and if the dust is massive, I'd rather not. I saw some videos of the sanding machine at work and didn't notice a cloud. I haven't measured these drums but they may have been turned many times.

[hoodeng]

Brake shoe flex is pedal travel.

Are you using a line lock?

Also, if the brakes barely hold or actually don't hold the car staging, what are they doing in the top end?

[Ron Gusack]

Brake shoe flex is pedal travel.

Are you using a line lock?

Also, if the brakes barely hold or actually don't hold the car staging, what are they doing in the top end?

Yes, I use a line lock in the water only. The brakes hold until launch rpm gets to about 2700. They work fine at top end, but this car isn't fast and I do 1/8 these days so lots of shut down. I might just buy new drums and check the fit.

[Dragsinger]

Something to consider, if the drums are over size [beyond spec] it will affect the shoe to drum fit. New drums most likely would be a good fix. Also, with some of the factory turbo cars are ungraded to larger wheel cylinders. You might check Buick Regal forum or other forums about brake cylinder upgrades for turbo cars.

Also, you mentioned check pressure and that is a good idea. The market offers a pressure gauge that screws into the bleeder screw opening. You might check into changing master cylinder size if it is called for. You will find master cylinder pressure sizing and usage charts with a google search

All food for thought.