The Stovebolt Site Forums The Shop Area Engine Shop Like to discuss brake drums if I may.

I’ve put about 10k miles on my 1950, 3604 since I did the complete brake work. http://www.pbase.com/dennygraham/image/114877862 The drums were in very good shape, not rusted, not grooved and not over size. They measured about .008” to .010” over the standard size. All that was necessary was a simple glaze braking with some 120 grit aluminum oxide paper. This is a rear but the fronts were in just as good of shape and they were only wire brushed. http://www.pbase.com/dennygraham/image/114877917

The first 6,000 or 7,000 miles they worked perfectly with a nice smooth stop from highway speeds on down, full hard pedal and you can lock them up if you needed to. But they slowly began to have this chatter as I applied them. And now I’m getting quite a bit of it during every stop. I’d also been getting a little brake squeal so I pulled the drums to clean things up and check for glazing. Every thing looks just fine inside, just the normal dust you would expect after 10k miles. So my ten thousand mile check up consisted of brushing off and vacuuming off the dust, de-glazing the shoes and a light scuff of the drums with, once again, some 120 grit. I also added a 45° chamfer to the leading and trailing edges of the shoe at this time. This was standard on brake shoes years ago but I haven’t seen it in years. Checked and repacked and adjusted the w/bearings, a full grease job and checked the kingpins (which were also installed new 10k ago) and checked newly rebuilt steering linkage and the toe in. A final brake adjustment and we’re ready for another 10k.
I noticed while I was adjusting the brakes that I was getting a tight spot or drag at one point, which of course indicates an out of round drum. Not a lot, just a little drag which is not all that uncommon with an older vehicle that has been in service for a while. However, I now believe that this is the cause of the chatter that I’m feeling. I don’t get the chatter during very hard application of the brakes, as in a panic stop, just during a normal application of them. There is also a very slight barely noticeable pulsing of the pedal.
I’m reluctant to have the front drums turned because they are not grooved and it is impossible to replacements, I’ve been looking for three years and I’ve picked up several spare sets but they are all badly worn and had already been turned well past standard so they are pretty much just door stops.
The other reason for my reluctance is that I can’t find any shops that will arc the shoes to fit the drum after it’s turned. And if I had them turned I would only want the bare minimum taken out and most shops are going to dial in a one pass, .060” cut so they don’t have to take several cuts and sneak up on the cleanup.
So I don’t really know what I’m looking for in this post, probably another answer to where the chatter could be coming from that I might be missing?
Denny Graham
Sandwich, IL

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Pete

Denny,
In all the years I did drum brakes I can't say I ever worried about arcing the shoes, they just wore in. I'm not saying it's a worthless idea,just that in all the years I twisted wrenches I never ran into the need for it.
It's too bad you can't find a shop that will turn off just a little of those drums cause that's what I'd want to do.
See Burger King, they'll do it your way !
Other than that I can only think of shoe material and that thought came to mind because of disc brake pad squeal,especially on Corvettes that was sometimes only cured by changing the pads to a different manufacture, which I spose changed the pad material composition.

Dan

I'm as dumb as a box of hammers when it comes to brakes, but I have some info that MIGHT be worth consideration:

My brother-in-law is not cut from the same cloth as us. He's into Dodge Power Wagons. (To each, his own.) He picked up a turning system for Power Wagons. You mount this device on the lugs, dial it in, and it turns the brakes to a true diameter. He picked it up at some ancient NOS place that was getting rid of all of their old stuff. He told me that it is "how they used to do it", and we joked that he got this thingamajig and will rarely use it, unlike a shop that used it to make money with it by using it frequently.


Take that and a dime and get you a cup of coffee!

Bill

Denny, I vote for the "out of roundness" of the drum or the brake shoe material. Its been a while since I worked on the old stuff....except for a recent Ferd, but brake shoe composition is a big factor these days. I recently changed some on a car three times before I got rid of the grinding sounds.
I have not got to drive my panel yet so I do not know what mine are going to do..... I have a set of extra drums that are turned but unfortunately they are for a 1/2 ton.

As an after thought, if there is a big tractor trailer shop in your area they are surely getting brake shoes recored by someone fairly close. If you could find out who those people are you may get what you want. I know there is one in Charlotte, N.C. ...or it was there not long ago. They can reline your cores and true then anyway you want them....with good stuff.

I nothing to add to the above, but may impose a question.

Why did your post about brake drums get moved here when there are many other brake related discussions still in the 'general truck talk' section?

Until the brake drums approach the maximum diameter (usually .060" oversize for cars, and .090" for trucks) there's no necessity to radius-grind linings. I grew up around a shop where we had the capability to grind brake linings, but we did it very rarely. Contrary to popular opinion, the linings were not matched to drum diameter, but they were actually ground to a slightly smaller radius so the center of the shoe would come into contact with the drum first. As pressure was applied to the shoes, the drum would flex slightly, and it would come into full contact for the whole length of the lining. A lining that's ground to the diameter of a standard drum will work a little better, not worse, in a slightly oversize drum. I'd suggest finding an old school brake shop, and see if they will take the time and effort to do a true-up on the drums with a mimimum cut. I'd be surprised if they need to make more than a .020" increase in diameter.
Jerry

Ditto what Jerry said. Something that is a big factor in the problem you're having is that the friction material hasn't had a good surface to seat in on. Brake friction does require a certain Roughness Average (R/A) to allow for proper seating on break in. I say do like Jerry suggests, find a shop that'll just true them up.

....rustednuts: general truck talk IS this! Don't mean to hijack the thread but why even have a general truck forum if you can't ask general truck questions.... everyone's opinion of general truck talk may be different but some that are moved are hard to understand. Everything "could" go under two forums. Either paint/body or engine/driveline, after all its ALL connected to one or the other!
But Cletis is the boss around here!

Cletis?.... what you smoking these days? I hear you once say you grow your own ...just kidding now!!! Thanks for what you do.

Bill from Texas, I've never heard of an attachment to true the lining on the vehicle. That would really be an odd one. When I worked at the auto parts back in the early 60's, arcing the shoes was a regular practice. In fact hand lapping the valves was the way I was taught to reassemble a head but thats also not done anymore.
We had a discussion going about a month ago that dealt with the very situation that you discribe. I did a brake job on a '50, 3100 with stock Huck brakes. Even though every thing, and I mean every thing in the brake system was new and the system was pressure bleed, the pedal still feels soft. Upon inspection after a couple of hundred miles my suspicions were correct. The drums were turned a sixteenth over and the shoes were only showing signs of contacting in a small area at the center of the shoe. The reduction in surface contact was only giving the truck about 10 or 20% of its braking power. I determined that the soft pedal was caused by the flexing of the shoes trying to stretch out to meet the drums at the ends.
Will they wear in and will the pedal firm up and will he have full braking power? Sure, eventually, but at the rate that I'm seeing now it's gonna take a couple of thousand miles. Now the one thing that I could not check is whether the relined shoes were actually sized to the standard diameter, if you know a practicle way to determine that radius accurately I'd like to hear it. So it's possible that the shoes were ground to a smaller radius than the standard and with the drums turned to the max so I'm ending up with a compound problem on my friend’s truck. I had no such problem with mine. One thing that I notice on his shoes when I installed them was that they looked like they were cam ground. They were thinner on the ends than in the middle by an substantial amount.
But back to my problem. I was contacted by someone that may be able to arrange for me to use a brake drum lathe to true up my fronts. That would be great. If I had my 16” engine lathe up and running I’d simply turn a standard gauge ring up to check the shoe radius, in fact I could turn up a set of large radius gauges, standard and no go. But alas, I’m a ways off on that lathe restoration.
Denny Graham
Sandwich, IL

Denny, a few tips for when you true up those drums. Turn the feed rate to it's lowest setting, then only take about .002-.004" cuts at a time. Might take longer, but you'll be rewarded with a much better finish and minimal material removal. Alot of guys go for a fast feed rate and a deeper cut (sometimes more than one) to get the bulk trued up faster, then do a slow feed fine cut, but I find that using a slow feed fine cut from the start actually saves time and preserves drum thickness. It also prevents premature wear on the cutter bits. I use this method both machining drums and rotors, and never have nay comebacks for noise or braking problems.

I use a grinding wheel attachment on my brake drum lathe. High spots are usually hard spots that don't cut well. I have cut drums and then checked them with a dial indicator and find them still to be out of round. The grinder is made by Ammco and my lathe is an AllTool 777. I kind of jerry rigged the grinder to work on my machine and it has enough reach to do my 7 1/2 truck drums. I also agree with longbox that slow feed and fine cut is the key to cutting them, but I use the grinder after I have cut them. I have never tried the grinder on my old jalopies, but I feel like I have saved a lot of $125 Centrifuse drums because today's linings are very hard on drums.

Well that's exactly what I've been talking about here Bill, the local machine shop is gonna take one pass which is the fastest way for them to get the job out the door, their not gonna smeak up on it like I would. I have a machine shop back ground and have worked in auto machine shops before so I under stand what your saying completely. Hope this pans out, that is me doing the machining.
Again Ken, I would really like to get my 16" engine lathe up and running and I do have a High Speed die grinding attachment the sits on the compound. I've ground lots of things on my 6" Logan lathe. I also agree completely with you about the hard spots and a tool bit. I run into shafting sometimes that has a hard spot and you will always end up with a high spot at that point. Since I don't see much wear in this drums I suspect that's the cause of the high spot that I feel when I adjust out the shoes. I normally would back off the shoe two or three clicks after it makes solid contact with the drum, but I'm still getting a little drag in one spot on both front drums. I suspect this is where my chatter is comming from when I brake from normal highway speeds.
DG

Unfortunately, grinding hard spots is only a temporary fix. As the drum (or flywheel) continues to wear, the hard spots become high spots again. A heat-hardened spot in a drum or flywheel is football-shaped, and the spot that shows up on the surface is like the tip of an iceberg. The only way I've been able to fix a hard-spotted flywheel is to machine the entire hard spot away, and that takes a really deep cut. Drums with hard spots are rarely salvageable, even if they're ground smooth.
Jerry

I checked with my brother-in-law about the shoe grinder, to make sure I wasn't spouting off something that was incorrect. He confirms my original post:

On the shoe grinder, you have it right. The apparatus mounts on the spindle. Measurements taken off the drum are transfered to the machine. Then the sanding disk is slowly brought into contact with the shoes until, after a few passes, the shoes are ground to perfectly fit the drums.

Of course, this assumes you have round drums to begin with.

Sounds like the OTHER way to skin the cat.

Bill

cletis isn't the only moderator in General Truck.

I moved it.

Not because it was in the WRONG place, but because the more technical minded guys with the actual KNOW how tend to frequent the Engine and Driveline forums, more often than General Truck. I know this, because I've been asking questions around here for years and years... and that is something that I noticed.

So... I was trying to help.

-W

The item you're describing is the "Barrett Brake Doctor". My father ground hundreds, if not thousands of brake shoes with the one at our shop back in the 50's. The other part of the setup was the "Drum Doctor" which was Barrett's name for their drum lathe.
Jerry

No complaints from me Woo.
Hey Bill I'd sure like to see a picture of that grinder, like I said I've never heard of one of them and I'll but most of the guys here haven't either.
Except Jerry. Hey there buddy, those must not have been made for quite some time, I didn't get one bite on the net for anything Barrett.
Denny Graham
Sandwich, IL

I found one listing on a Google search, from another old car/truck site. Try a Google search for "Barrett Brake Doctor". There's a pic of the unit in a box, but nothing showing it in use. As I remember, there were several adapters to fit different spindles or axle flanges, and a high-speed grinder disc that put the radius on the shoes. Asbestos dust everywhere, even though it had a "dust catcher" bag on it!
Jerry

These guys list 3 different brands of brake shoe grinders for sale. Scroll down to the bottom of the page. http://www.allstates.com/BrakeClutch.html They used to be very common and they all kind of work on the same principle. There were several of them in shops in town when I was growing up. I never bought one. I'm sure they sold for a song when the old shops were liquidated. I haven't actually seen one around for quite a while.

Try this link, Denny:

http://forums.aaca.org/f120/barret-brake-doctor-267451.html

Jerry

Saw that this afternoon Jerry and down loaded it to the archive. Interesting set up. I'd like to see what kind of grinding tool were came with it.
Ken that Barrett Brake Shoe grinder is very close to the one we had in the auto parts shop I worked in. Not sure what the brand was, that was almost 50 years ago.
DG

As I remember, it was a disc sander about 4" in diameter with some type of guard/dust collector that was supposed to catch the grinding dust. It didn't work all that well! The little electric motor must have been a 3500 RPM type, because it really got wound up in a hurry. The trick to doing the job right was to take several very light cuts to avoid stalling the motor down.
Jerry

I printed out that picture to study it, and of course with parts of the puzzle missing one can only guess. But the motor appears to have a long shaft at the business end. My guess would have been that they used a type of drum sander similar in principle as the Barrett Shoe Grinder.
DG

Thanks Guys - All these years later and your experience and wisdom is still at work helping me with my brake shoe/drum inconsistencies and questions! (now I just have to fix them)

Doug