I've read through a bunch of threads, and i'm just looking for opinions on two different fixes. I have a model a axles, '39 backing plates and wide five drums. On the rear, do i mount them upside down, or rotate them slightly and re-drill? Thanks
I think you just need to elongate the holes in the backing plates, if you were to turn them upside down you wouldn’t be able to bleed the wheel cylinder correctly. I’m sure someone who has done it will chime in.
That's on the front the the hole needs to be elongated. The rears bolt up. I've never turned the plates upside-down. But when you do, you also flip the wheel cylinder, so the bleeder is still up. Personally I like having an ebrake, so I rotate the plates. It should be noted the lip of the backing plate needs to be shaved down 1/8th of an inch or so...or maybe it's 1/4. I can't remember. And the same on the inner lip of the drum.
Getting ready to do the same proceedure with 40 rear brakes on Model A rear end. https://www.lainefamily.com/ModelAFiles/ModelABrakeUpgrade.htm
I've read that article, lots of good info. I wonder if the drum/plate interference is due to the later drums? I might be alright with the wide fives. I also bought some taper shims which are supposed to help if your drums rub when everything is stock. If i switch the plates left to right, the e-brake tube will be pointing forward. What i need to figure out, is if the cylinder casting will allow them to be flipped. If so, the bleed screw will be up, and the big shoe can still be forward.
As I remember 39-48 backing plates are the same for std brake drums. You may have to file the holes a bit. The fronts fit on later32-38 spindles with and adapter ring and a sleeve for the drums.Never had the occasion to work with five. They were considered odd ball in early 60's
My avatar car has '40 fronts and '46--48 rears. The only thing I needed to do is cut off the original shock arm ball for clearance at the top of the rear backing plates. Other than having to use round back spindles on the front and the appropriate steering arms and tie rod, everything bolted right up. There is often the problem of drums rubbing the backing plates. Easily fixed by turning a little off the edge of the drum on a brake lathe or using axle shims to space them out. Around here, the shims are easier as there's no brake lathe anywhere near here. One shim will usually do the trick. Be sure you put the fiber washer behind the axle nut and washer. Tighten to specs - very important.
Thanks for all the input. I found an old whl cylinder and confirmed that you can't just flip them over. The mounting holes are offset to the round part of the casting. I'll figure something out.
If you don't plan to use the stock shock mounts on the A axle simply cut them off and the V8 backing plate will work fine bolted straight up. You can also bolt them straight up by shortening the shock mount about 3/4 to 1-inch. That combined with a little filing will allow you to get brake lines connected without rotating the backing plates, The picture shows the shortened shock mounts on my open cab pickup. Dogbone links fit Model A lever shocks just fine. My rear brakes had an 1/8 taken off the backing plate and drum as described above. I still ended up with an axle shim on each side due to end play on the axle shafts. I have had no problems with the shims; axle nuts must be tight!
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