How to arc brake shoes...

[Jim Saraceno]

How does one arc brake shoes? I recently replaced a pair of brake shoes and the squeak like crazy at a full stop. Can the lack of arcing contribute to this problem?

[Jerry Roberts]

There is a special machine for this , they are getting scarce though . One member arced his shoes by putting self adhesive sandpaper in his drum and rubbing the shoe on the paper . You could check to see if your shoes match the curve of your drums by placing the shoe against the arc of the drum .  You could get on the phone and call around to see if someone has the machine too . 

[rallyace]

Check with other old car folks and see if someone local to you does the work. If not, check with shops that do a lot of heavy truck repair work. If they don't do it themselves they can direct you to someone who does. Locally (Syracuse, NY area) we have one shop left that does the work and they get enough brake work from the old car hobby folks to keep providing the service.

 

[PT81PlymouthPickup]

My dad owned a repair shop from the early 50s up until late 90s. He had a Ammco brake lathe and shoe grinder. Anytime we turned a drum we would resurface the shoes to exactly match the radius. That's in the days the drums were worth re-cutting. I used to love the smell of all that asbestos flying around. Lols! The machine was in a back room with no ventilation.  Anyhow, when we finished a brake job, the cars stopped like new. If your drums are not standard dia. and you install shoes without grinding, they often will squeal and could make the car pull to one side or the other until they wore down to match the radius. Also, some lining materials were more prone to squealing than others. I'm sure there's some that still do this, but beats me where? 

[Dodgeb4ya]

A typical shoe arcing machine.....

[James_Douglas]

What is interesting is that in the early Ammco arcers when using the machine you had to do the math for the clearance and then set the dial. In the later machines, I have the insert to the instructions, they built the clearance into the machine so you just set the dial.

 

I have seen people with problems that had shoes arced in an Ammco machine and it was because the operator did not know which machine they were using.  They look the same, the only way to now about the change is by model number.

 

James

[Jim Saraceno]

Thanks for the info. I was thinking that was the way but I wasn't sure. My history on brakes is... When I first bought my '35 Plymouth in 2003, the brakes were fine. I actually wondered why people complained about drum brakes. Then one day I applied the brakes to slow down and the right rear wheel locked up. When I started up again the pedal went all the way to the floor so I had to make it back home with just with down shifting and the hand brake. When I opened things up I found one of my brake shoes had just disintegrated.

 

I send all my shoes off to a place that Don Coatney had recommended to be re-lined and after I installed them the car never stopped like it did with the old shoes. I assumed it had to do with the newer non-asbestos linings but I suppose it may have had something to do with not being arced. On the other hand, I have to assume that the shoes would eventually"arc themselves" as they wore in but the braking never got any easier.

 

Then this spring I notice one of my wheel cylinders were leaking. When I pulled the drum I saw one of the linings on one of the shoes has separated and fell off the shoe. I ordered a pair of shoes from Bernbaum and installed one pair with the intention of installing the other pair when I had more time. The new pair started squeaking right away and haven't stopped yet (probably 4-500 miles).

 

So with your information, I'll take that drum off again, check to see how well the shoes are arced, readjust the shoes and see what happens. If that doesn't do the job I'll start calling around to see if I can find someone local to do some work (though that just really goes against my grain!).

 

Thanks again.

[PT81PlymouthPickup]

Besides the proper fitting, the material has a definite effect. Even in the old days when linings were full of asbestos, they were not all the same. At my Dad's shop, we used to stock Bendix and Pennsylvania brands. The Pennsylvania linings were softer and rarely squealed, but did not last as long. The Bendix would often squeal but wore like iron. I can't remember now which one, but I remember my dad saying one seemed to stop the vehicles more quickly. I would think the softer material? You could also get riveted or glued. Not having all that much faith in adhesives, I choose the riveted when there is a choice. Now days, the reproduction stuff we buy for our vintage vehicles is a real crap shoot if it's a quality product. Even the old American brand name stuff is coming from China. Be careful!

[Dodgeb4ya]

 Softer linings work better for the old MoPar Lockheed brakes IMO.

I have mostly asbestos old stock linings on my cars now days.

Perform like they used to...predictable and stop safely both cold and hot...but not fading hot!

There are too many poor performing modern day linings sold that don't work well on the fixed anchor Lockheed brakes.

[westaus29]

Reading the comments above gives me a better understanding of why so many people have problems with Mopar Lockheed brakes. Despite living in an outpost of civilisation in West Oz, we are blessed with Perth Brake Service that has been there over 40 years, offers advice, a choice of lining material, reliable bonding service, drum refinishing and matches shoes to drums. They also resleeve cylinders and source rubber parts. First used them for my 29 Plymouth in 1979, have done lots of brake jobs for kids, and two more Mopars (38 and 55) since with zero issues, even did a Pommy Daimler with hydraulic front and mechanical rear for a friend. It is a 100 mile round trip times two to get there but well worth it.

 

For reliable results in such a critical area you really have to find a way to cover all those bases.

[Slickster]

I'd bet there are alot of older cars out there that have had their brakes shoes replaced without arcing them....is it a true safety item or do the shoes eventually wear some getting the %100 contact?

[P15-D24]

20 hours ago, James_Douglas said:

What is interesting is that in the early Ammco arcers when using the machine you had to do the math for the clearance and then set the dial. In the later machines, I have the insert to the instructions, they built the clearance into the machine so you just set the dial.

 

I have seen people with problems that had shoes arced in an Ammco machine and it was because the operator did not know which machine they were using.  They look the same, the only way to now about the change is by model number.

 

James

I have a set of factory instructions for the Ammco unit somewhere. If I can find it I will post it in the Downloads section. 

[P15-D24]

6 minutes ago, P15-D24 said:

I have a set of factory instructions for the Ammco unit somewhere. If I can find it I will post it in the Downloads section. 

Found it!  It's uploaded now in the Downloads section.

[Dodgeb4ya]

BTW....There are at least four different Ammco arcing machines.

Parts and design are different between them.

All have their own specific operating manuals?

Also more manufactures of shoe arcing equipment say like Star Machine...FMC etc.

[James_Douglas]

The instructions are different for the units with the built in clearance and the ones that do not...use the wrong one with the wrong instructions and you will be off by a lot.

 

Here is my set of operating instructions for the model 850 and 8000 and later units with the built in clearance. See the addendum file. It is hard to read so I retyped it and added it to the end.

 

James

OneFile1750 Ammco.pdf

[PT81PlymouthPickup]

17 hours ago, Slickster said:

I'd bet there are alot of older cars out there that have had their brakes shoes replaced without arcing them....is it a true safety item or do the shoes eventually wear some getting the %100 contact?

Yes, there are a lot of old cars and some not so old that have been worked on by un-knowledgeable mechanics, which could make them unsafe. Brake shoes will wear in eventually, but that could take several thousand miles. Vehicles with front drum brakes can be especially unsafe if not assembled / arced properly causing them to grab and could pull the vehicle to one side in a panic stop. Rear drum not done properly can cause safety concerns as well, but I believe not quite as critical as the front. We sometimes forget that automotive brake systems were / are highly engineered. Anytime we change things like replacing shoes with wrong radius, replacing drum brakes with discs, different sized wheels and tires, different sized master or wheel cylinders, different lining materials, adding proportioning valves, etc. etc. will deviate from original designs. If one is not careful, it could easily make a vehicle unsafe. Often I have read of repairs and modifications that anecdotally are reported as working perfectly, but in a panic stopping situation it may cost you your life.  Sorry to be a drag!

[Dodgeb4ya]

The clearance MoPar suggests at toe/Heel is .006"

Ammco .030" smaller than drum diameter..same toe/heel.

The type of lining material can require a supposedly specific clearance.

A brake guy I used to have a lot of shoes relined over the years once told me to make sure the toe and heel are not the contact areas.

Too much toe/heel clearance will of course cause soft springy feel pedal...can also cause the center of the lining to glaze.

I have always arc'ed the linings to fit the drums at 90%+ contact to the drums.

I always did it by eye...not the micrometer reading.

A high firm brake pedal is what the customers need at completion of a brake job.

Edited November 25, 2020 by Dodgeb4ya

['41 Fat Bottom Girl]

This is so easy to do! And you don't need to find somebody with an arcing machine.

Fitting the shoes to either a new or refinished drum is important for good braking and wear, but isn't difficult to do by yourself and doesn't take much time at all. Remember, each set of shoes should be matched to each drum- drums may not all be the same diameter inside.

I've used this method over the last 50 years on my many drum brake jobs and have always had great results. It has  giving me the right arc, proper clearance without point contact at the heel or toe of a shoe, and perfect drum contact over the proper shoe surface.

What to do- 

Get yourself a variety pack of different grit sandpaper.
I have used either 100 grit (if I need about .020" thickness) or 60 grit ( if I want about .030 thickness). You can pick what you need. Do check the caliper on the paper you are using, different brands of sandpaper are a bit different in thickness.

Cut the sandpaper into a couple strips the same width of the surface inside the drum. On the back of the sandpaper, apply double-faced adhesive tape, then stick them inside the drum butting the two strips together. Clean the drum surface first to remove any oil.

You can then take a shoe, holding it tight against the sandpaper and slide it back and forth around the inside of the drum. Sand it until you have contact along the entire face of the shoe. Keep it flat to the sandpaper. 

Do both of the shoes that will go into that drum. 

Lastly, make certain that you have about a tenth to 1/8" chamfer along the heel and toe of the shoe lining. You can do this easily with a file if the shoe doesn't have a good bevel at the ends. 

It's fast, doesn't remove much material and works great!

Hope this helps.

 

 

[Jim Saraceno]

Great idea, Thanks! I'll give that a try.

 

[Sniper]

DO NOT BREATHE THE DUST

 

I still have a stash of genuine 3M N95 masks from my master bath remodel job.  Getting hard to find good ones.

[Jim Saraceno]

Yeah, I still have one N-95 left and a respirator. Thanks.

[9 foot box]

   Jim, are you adjusting the anchor bolt for the shoe for the major adjustment?

[Jim Saraceno]

Sure. The only thing I don't have is a tool to pre-adjust the shoes before I put the drum on. I try to get it close then do the adjustment when the drum goes back on. Major first, minor second. That has worked for me for many years but this is the first time I've dealt with a squeaky brake shoe.

[DJ194950]

Did you sand the drums and shoes with some medium to course sandpaper when installed.

 

Always a part of my repairs.

 

Only once on a old Datsun 280 Z did I have front brake squeaks. Talked to the dealer parts about this and said the replacement pads where too hard for the car and to get factory replacements which I did and sanded the rotors again and installed, no more squeak!

By the way they did not cost more than the aftermarket parts either!

 

Maybe yours are also too hard of a material on the shoes??

 

DJ

 

 

[Jim Saraceno]

No, I didn't sand the drums or the shoes but that is next on my list of things to do.