if you buy the repop drums be warned. you still will have to turn and balance them. my friend tested a brand new one and the contact patch was 1.5" on each side of the braking surface.
Where was the small contact surface on the shoes? There is an adjustment procedure laid out in one of my many old manuals that does not require any special tools except the wrenches used for the lower eccentric and the center adjuster.
If you are using DOT 5 (silicone brake fluid), your wheel cylinders need to be perfect. This stuff will wick through any slight imperfection in the cylinder bore and contaminate the brake lining material. If this occurs on one side and not the other, you end up with brake pull to one side - a dangerous situation. This is just something to consider when diagnosing the entire hydraulic brake system!
Yep the repop drums and shoes I put into the '40 rear brakes on my AV8 needed to be radiused to match up. There's really no avoiding it - or at least checking that it is right. It's not rocket science - in fact they were doing all this stuff before rockets were even invented. I had to sand down the middle part of the shoes a bit (not much) to get them to match up nice. There was plenty on lining thickness available so no issue there - I did have to back ALL of the cams and eccentrics all the way off to get the new drums over the new shoes at first. After a few miles I pulled the drums to check how things were and they were pretty much bang-on right - which is why the brakes on this little car work so well. Easy-peesy! Don't know what all the fuss is about really...
New drop/-on late model drums usually need turning, early Ford modern replacement ones (the replacements are not made as a unit like OEM) require presswork and are always going to need turning. Shoe diameter is only going to be right on drumas that are at original 12" even, and of course the original 1939-42 centering adjustments cannot do the job until shoes and drums are bot on the same radius.
Bruce, It is interesting you said shoe diameter will be right on or drums that are 12" even. I tried to put drums on with new shoes. All my drums were NOS. The drums wouldn't it over the shoes and I found out that the company that lined the shoes routinely arced all shoes for a 12.030 drum assuming that everyone would be out at least that amount. Charlie Stephens
Right in the center of the shoes. Both from and rear and even on both sides. If it isn't the center maybe just a tad north of center. Posted using the Full Custom H.A.M.B. App!
I'm running Skydrol.. Just kidding. Yeah I got the right stuff. Good point thou.. Posted using the Full Custom H.A.M.B. App!
So someone is oversizing the shoes without notice to the users...good kludge, bad communications, especially with new drums available again! There have been similar kludges on engine parts in the past, based on assumption that an old engine must be getting the new rings tossed into a worn and taper cylinder. Anyway, since no one is making drums with hubs in and final machining done that way like originals, everything needs to be checked out and cut some anyhow. I'll keep on hoarding decent originals... Also...the "north of center" probably indicates need for another run on lower adjusters.
If your contact patch is right in the center that means the drums are larger diameter than the shoes. Probably coincides with the warped drum problem you have>>> Your drums are cut oversize, and may be too thin. Replace the drums with some good originals (best option), or reproes that are properly turned.
eBay has a aamco brake lathe and shoe arch. It's a beauty to. I found a guy on gasoline alley that may be able to help. He's the only one around. May need to ship them out Posted using the Full Custom H.A.M.B. App!
So I need to do more work on the '34. I converted to self energizing front brakes from Speedway with some improvement. Living in the "boonies" gives me some room to stop but I am worried about the brake power. Is there something to use to "blue" in the fit without driving the car? I am thinking to use a guide coat of paint on the linings, Agree?
You should always set the shoe inside the drum before doing anything. See if it matches the curve of the drum, or does it rock like a rocking horse? Contour grinding is nothing more that making the curve of the shoe, fit the curve of the drum. Some of you might have a body work or horseshoeing file, these work well for reshaping the linings, or other types of coarse, sharp files.
40 brakes have an eccentric anchor bolt on the bottom of the shoes; Improper adjustment can give poor shoe to drum contact. Ford itemized a step by step proceedure for doing a "major brake adjustment". It takes some time to do, but worth it. 4TTRUK
You could use spray DYKEM, machinists blue in a spray can, puts on an almost anodized looking guide coat, that would be better than paint.
Thank you F&J and indyjps. I will do the fitting with the shoes removed, that makes sense as opposed to sanding / install drum / sanding again.
Make sure the brake lathe has a small shaft, or the rear hub will not go through the newer shafts,. Chris
Motorcycle guys with drum brakes glue 80 grit paper to drum with contact cement. Then they spin the wheel and slowly apply pressure to contour shoe to drum. They say it makes a big difference on motorcycles. Ago
How do they get the sandpaper off after? Contact cement is not difficult to remove, Dick suggests Brakleen. Ago
That's what I was thinking, but could you just hold the sandpaper in the drum and slide the shoe back and forth inside the drum...this may be easyer said than done
Well, I would think about using a deceased drum cut away as a gauge for the shaping...you could then see and measure distance from shoe to drum all around. Presumably you would be using a drum rejected for heavy wear, so get it turned to round and smooth regardless of size before cutting out a section, then just add the difference between this gauging drum and the drum you will use into the feeler gauge you use checking your results.
I just recently picked up an A w/ these brakes and they need work. Thanks for all that replied, I feel like I have a head start. Bookmarked.
I have done this. I used 80 grit longboard, ( on a roll, sticky on 1 side). I trimmed the excess width with a razor blade...it worked quite well
One thing that many people don't realize is how differently early Ford brakes and Bendix self-energizing brakes behave. The earlies respond to foot pressure on the pedal in a fairly linear manner, stomp harder and they stop harder in proportion to your stomping power. This is rather like a disk brake, which also lacks self application power. Self-energizing brakes, oddly enough, self-energize...this means response changes in a non-linear manner in relation to foot pressure as the self application cranks in. A very small change in stomp might be the difference between a smooth stop and a face-plant against windshield. Typical Detroit power assist had almost no feel in drum brake days, and a sensitive foot was required. Neither is hard to get used to but they do differ quite significantly.
Dredging up this old thread to ask a related question. I'm running '39 wide five wheels and drums on my '32 3w, and I've begun asking around my area mechanics if anyone can turn the rear drums. Everyone so far seems able to turn the front drums, but the rears pose a problem because the typical brake lathe shaft won't fit through the small tapered hole of the rear drum. Buying new drums isn't an option as far as I know since it's only the '40 up drums being repoped. Can anyone post a pic of the proper tooling required to chuck up a rear drum? I could probably machine something to do the job if I could see what it looks like. Thank you in advance.
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