Technical Juice Brakes On An A Rear End Question

I decided to run 1940-48 hydraulic brakes on my Model A rear end. Besides inverting the backing plates and running the correct corresponding drums & hubs, is there an adapter I need? I've always just ran stock mechanical brakes but am stepping it up on this next build. I already knew an adapter was needed for the fronts but not for the rears?

 

I put 40's brakes on the Model A rear end in my Hot Rod. It's still being built so I haven't driven it yet. I didn't invert the backing plates or do anything else other than bolt the parts together. I did do a little bit of grinding on a couple of pieces which had some interference, but that's all. A street rodder friend came over and looked at it and told me I couldn't do that. But I did it before he told me that, so I didn't know any better. I can take pics of it tomorrow when I'm at my shop.

Mike.

 

Do your drums clear the backing plates?

 

You're gonna need to take off like a 1/4 inch on the backing plate lip and the inner drum lip.

Sent from my SM-G900T using The H.A.M.B. mobile app

 

The backing plates bolt right on and inverting and swapping them is what I did. No problems at all. You do NOT need to grind the backing plate if you use a shim on the Axle shaft. I think it was .015 stock and most Model A parts suppliers have them. I've had No problems at all.
The Wizzard

 

As hitchhiker said, you may need to grind a bit off the lip. I used axle shims on mine and did not need to grind much at all.
I inverted and "flipped" as you mentioned. No adapter needed. But if not mistaken, the backing plate needed to be altered as the wheel cylinders need to be reversed.
I posted on this thread years ago...
http://www.jalopyjournal.com/forum/threads/rear-brakes-hub-question.338632/#post-6849853
Hope it helps

 

Here's another way to do it without inverting the backing plate or relocating the mounting holes. The two problems with bolting on the backing plates straight up are access to connect the brake line to the wheel cylinder, and access to the bleed valve. I solved both problems by shortening the shock bracket located above the spring perch by about 3/4 of an inch. The shock mount was cut off, shortened, and then welded back on after vee-ing the joint on all four sides. Since I was lowering the rear of the car anyway, shortening the bracket also helped out with maintaining enough travel in my lever shocks. If you are going to run tube shocks you could cut the shock mount off flush with the top of the perch.

Like the other posters I cut about 1/8-inch off of the lip of the backing plate, and had a like amount cut off the inside edge of the brake drums when I had them turned. With this modification I didn't need any axle shims to provide enough clearance between the drums and backing plates.

 

Excellent advice fellas! Thanks. I'll be starting my build thread soon. I just wanted to get a lil further along first. She WILL be road ready by summer!

 

OK, here are some pics. Please disregard the white stuff all over everything, it's just splatter from rubbing out the paint. Here's the overall view.




I removed the shock mounts from the perches and used aftermarket parts for the tube shocks. Here's a closer look.



It took just a slight amount of grinding on the perches for clearance for one of the m/c bolts and the fluid line, but that's all. No t******* of the backing plates or drums.



As I said, I haven't driven the car yet, but nothing is rubbing on anything so it appears this all will work out fine. This is a stock Model A rear end which happens to be a very low-mileage unit. The whole ch***is from which this rear end came had very little wear. I gave the Model A brake parts to my Model T mentor, who also was a Model A guy (he p***ed away a few years ago). He said those brake parts were the best condition he had ever seen for used parts. I mention this only to point out that maybe that has something to do with my "getting away with" not needing shims or doing any grinding on the other parts. I really don't know why it all went together fine for me, when many others obviously have needed to do other work to make this combination of parts work together. Maybe I just got lucky this one time.

 

Thanks. That's very helpful.

 

No ones mentioned the smaller bolt circle of the model A. Holes need to be slotted in the backing plates or plugged and re-drilled.

 

The big hole in the center of the juice backing plate needs to be enlarged to fit.

 

So are you guys just using front backing plates on the back? I'm not seeing any park brake parafinailia.

 

So far we've only been talking about the rears. As far as I've been involved all 5 holes are a Match using Model A axle housing to Hyd REAR backing plates as well as having E brake units.
The Wizzard

 

I'm using rear backing plates and all the e-brake parts are installed except for the cables. Will get to those later.

I'm not sure what this is about, but I didn't have to do any of that stuff.

Didn't do this either.

 

Yes.

 

Using rears on mine. Flipped upside down, the e brake hole comes in from the top.
http://www.jalopyjournal.com/forum/threads/rear-brakes-hub-question.338632/#post-6849853

 

Great! So i just collected what i think would be a 39' complete rear, has juice brakes but is a wide 5 bolt pattern. So I should be able to use those backing plates and then scrounge up some 40'+ hubs and drums right?

 

^Yep

 

LSGUN was correct (Yep) but I wanted to add that the wide 5 bolt pattern hubs/drums are not reproduced and probably worth more than the 5 on 5 1/2 drums if they are in good shape. That look is coming back. Trade or sell outright.

Charlie Stephens

 

You heard him folks, who wants to trade?

 

Found this link today, worth a read http://www.lainefamily.com/ModelAFiles/ModelABrakeUpgrade.htm

 

That link has always had good info. Indexing or "clocking" the backing plate is another viable option.

 

It's always amazing how much work some people can make a Simple job become.
The Wizzard

 

True. Many ways to skin this cat. Just pick one and get ******!

 

So what is the consensus on the front, normally I'd just change to 40'- 48' from the king pin out, any way to retain the Model A spindles and drums? I'm putting together another speedster and want to keep an early look, but the mechanical brakes really took the fun out of driving the last one.

 

Model A spindles yes, using the spacer ring from Mac's or any vendor for the '40 backing plate fitment. You can usually use a file to oblong the backing plate holes to fit the A spindle. Then you're all set for a 40 drum and all the internals.
Drum from model A doesn't work.

 

Here is one of my old axles. 4" Dropped Model A with Model A spindles, king pins, steering box and Tie rod with 46-48 Brakes.

 

I hate to get picky but with the adjusters on the bottom the brakes are prewar.

Charlie Stephens

 

Aww F--k!! I made a mistake. Plus it's a 4-1/2" dropped axle. I guess I'm just to Old to be of any help any more. Thanks for pointing that out Charlie.
The Wizzard