Technical Self energizing brake upgrade and lessons learned for any homemade backing plates

My 27 T is running '34 Plymouth spindles on a 48 Ford axle up front and a 34 Plymouth rear axle. I was never able to get the stock Plymouth brakes to work very good....not sure why, the brakes on my 39 Plymouth worked just fine, but those '34's.....Well after going through a stop light while standing on the brakes, I finally decided enough is enough!

I recently clipped my '65 Chevy truck with '89 Suburan and swapped the rear end as well, thus I had 4 good bendix style brakes to put on my T.

I cut the center out of the Plymouth backing plate, then centered and traced the Plymouth cut out onto the Chevy backing plate. Then I bolted the center of the Plymouth backing plate to the spindle, put the hub and drum on and eyballed the centering of the Chevy portion of the backing plate using the drum as a guide. Then welded the two pieces together. One can judge by the welds in the first pic where the two pieces fit together. Lesson learned...Don't "eyeball" or "finger-judge" the centering of the backing plate in relation to the drum, in the long run it worked out (via a big hammer to "adjust" the backing plates) but, I should have built a jig or did something else to make the backing plate more precisely matched to the drum.

The big problem with this swap is that large flange on the bottom of the Plymouthspindles. That flange is used for mounting the steering arm and to mount the lower pivot of the stock brake shoes. Problem is that it sticks out, towards the wheel, and gets in the way of the '65's brake adjuster. I got it to work by weld, grind, test fit, grind, weld, test fit....

 

For the hubs and drums: The center hole in the Chevy backing plates are about an 1" larger in diameter, so I built up the flange on the hubs and turned them on the lathe. Then pinned the drums to the hubs for indexing purposes (for future dissasembly and reassembly). I used the Plymouth lug bolt holes as a guide and drilled the Chevy drums.

For old tool guys, notice the lathe is older than the model T! Best I can tell it was built around 1920, because by 1930 South Bend put the motor under the bed. And if it were too much earlier than 1920, it would have been driven by an overhead belt, not a motor. The current motor is not from the 20's, probably 50's.

 

Assembly pics...

I decided to go with stock '65 Chevy brake hoses ($11.99 at Auto Zone). They were too short to go to the frame so I ran them to the axle then used a '89 Chevy rear brake hose (the Tee has a convienent bolt hole in it) to go from the axle to the frame. I was a bit concerned about the overall look, but it makes the front end look really clean and I'm very pleased with the decision.

I put the Chevy brakes on the front and the rear and I'm still using the stock '34 Ply master cylinder.

The result....The car stops on a dime! Without exagerating, it honestly stops as fast a disc car from the 70's or 80's! I am truly surprised at how fast it will stop on the stock skinny bias plys. I used to be concerned that the traction of the tires was a problem, nope, not at all, those tires work just fine.

One thing that is taking a bit getting use to is that the brake peddle goes down about 3 - 4" before the brakes start to engage. But once they do they are solid and only go down about another 1" before the tires are locked, which only leaves about 1" to the floor. Perhaps the Bendix style brakes need more fluid to move them outward before engagement with the drums than the old pivot-at-the-bottom type of brakes.

 

Cool upgrade!

 

You are fearless, that's for sure.
The pedal almost going to the floor is the fly in the ointment for the short term.
Long term, what problems will arise from the pioneering effort?

 

What size is the lathe? My 9" is from 1934, first year for the 9" tool room lathe, and the motor is not under the bed, but behind. Check out Lathes.uk, lots of interesting stuff there.

P.S. Good job on the brakes.

 

The most likely problem causing the extra free play would be that the brakes need to be adjusted, but if the brakes are properly adjusted, you may need to replace the master cylinder with one that has a larger bore. That will push a higher volume of fluid and cut down on the free play. The down side is that the larger bore would increase the pedal effort once the free play is taken up.

 

Well, when ya try something new, there's always a learning curve....

The top "pin" that the shoes fit onto was originaly screwed into the '65 spindles. I decided to see if the backing plate was strong enough to just bolt the pin to the backing plate. The rears are like this, but they are made with a heavier gauge. But this did not work. As the first attachment shows, the backing plate bent. It also broke both wheel cylinders because the pin is used to mount the wheel cylinders.

So I made a plate and welded it in to stiffen the backing plate around the area of the top pin. This worked well but....see next post.

PS. Richard D - the lathe is a 16" x 36"

Kipp

 

After stiffening the top pin that the shoes rest against, a new problem arose, the front brakes dragged. It was like driving around with one foot on the brake. They would drag until I went backwards and hit the brakes, then the shoes would "release" and I could go forward without them dragging until I stepped on the brakes in the forward direction, afterward they would drag.

I suspected the main top pin was too low or too high and the shoes were getting wedged between the pin and the drum. I used some machinist dye on the shoes to see where they were hitting the drum at. On both sides of the car only the bottom of the shoes were engaging the drums. Then I pulled the drum off the hub just a bit, enough to clear the centering boss on the hub and used the brake adjuster to adjust the shoes out. The first attachment shows where the brake shoes and thus the top pin, wanted the drum to be. The drum needed to be lower by about 1/8".

I concluded the pins were too low with respect to the hubs and would have to be raised. I also wanted to raise the pins that hold the shoes to the backing plate so they wouldn't be at some goofy angle and cause problems. I cut the backing plates in half,****embled the shoes to the top half and adjusted the brakes all the way out. Then I mounted the drum to the hub and welded the two halves of the backing plate together (not shown in pics).

I have the driver's side back together and the drum fits better and adjusting the shoes is acting like normal.

We'll see....

Kipp

 

All back together and works like a champ!

SMOG_GUY, you were right about "The pedal almost going to the floor is the fly in the ointment for the short term." The problem was that the shoes were too low with respect to the drum, so there was a lot of extra room for the top of the shoes to move outward and take up.

With the shoes, due to the top pin, in the correct position, the pedal is rock hard at about 1" travel, right where is needs to be. There is no pulling, no dragging, no stupid stuff. hmmm, kinda works like a '65 Chevy truck....only better.

Lesson learned, to locate the backing plates correctly, and more specifically the top pin,****emble the shoes on the backing plate, put them in the drum, shim the backing plate off the drum approx. 1/4" and adjust the shoes outward so they are tight in the drum. Then bolt the drum to the hub and weld the backing plate in place.

Hope this lesson can help someone in the future,

Kipp