Model A Ford Brake Parts
Reproduction parts compared to originals.
Through a some kindness of another person I was able to acquire some New Old Stock Ford brake parts. I have also purchased some reproduction parts. I have two goals. First is to make the brakes on my cabriolet stop like factory. Second is to learn which reproduction parts can be used to accomplish the same goal as the first. To make my cabriolet stop like factory I have been attempting to acquire as many NOS Ford brake parts as is possible. This is tough as NOS parts on Ebay have been out of my range. There have been reports that many of the available reproduction parts are just like factory. Having been the victim of bad information in the past I have been attempting to learn what the factory part dimensions really are so I can properly compare.
In comparing parts, we have to consider how exact the parts are to the originals. We also have to bear in mind some parts can be off in dimensions and still be functional. In the brake system many parts are kept under compression or tension which removes all the play.
Here on this page I will keep to reporting differences I found between reproduction and original parts. The reproduction part were purchased from Bratton's, but I believe they are the same parts most all venders carry. Please bear in mind, I am in no way saying that Bratton's is making a bad part in what I am reporting. In fact, Bratton's is a reputable company and is were I have been buying parts. There are many other very reputable suppliers on the market and this is not intended to push Bratton's, I have bought and will buy from any of the parts dealers with no reservation. As with any purchase it is wise to ask whos parts you are buying and if they have the correct properties. For example; the rear brake camshaft I bought from Bratton's came in a Synders package.
Brake rollers are pushed out by the cam or wedge. It is important that the rollers be round and hardened. Frequently the originals will have a flat spot because the roller stopped rotating. The reproduction rollers that are available from some if not all A suppliers are hardened. All were nominally .250" thick.
|Original (8 NOS)||Repro (a full set)|
|Inner Diameter||.436 to .438||.437 to .439|
|Outer Diameter||1.248 to 1.250||1.247 to 1.249|
I had one NOS Inner Dia. at .431 which is too small to allow the roller pin to fit.
I had 3 reproduction rollers at .445 which allowed for slop on the roller pin.
Brake roller pins are a very important part of the rebuild. The originals are almost always worn with a flat spot. They are responsible for positioning the brake shoes so the shoes will always have full contact. The reproduction roller pins that are available from some if not all A suppliers are hardened. I did not have any NOS Roller pins, but I found unused parts of originals to compare to reproduction. The used original dimensions are from 'averaging' the unworn areas.
|Major Diameter||.618||.618 to .620|
With the reproduction pins I had one that the end where the cotter pin goes was .436 and the rest of the shaft was .435.
Adjusting Shaft Pin
The reproduction adjusting shaft pin looks like it was stamped. It has very poor form. The reproduction measured .430 on the minor diameter. The originals are not likely to be very worn and out of the pile of used pins I have were close to .434", this is as expected since they should be the same diameter as the roller pin.
Rear Brake Cam Shaft
I have a pair of NOS rear brake cam shafts. I was real happy to get these as I felt this was a important part to have fit correct. I have two NOS original shafts and two reproduction shafts and so the table has two values for each measurement.
|Shaft Diameter||.685, .684||.685, .686|
|Length||2.837, 2.841||2.847, 2.890|
|Pin Hole||2.303, 2.300||2.300, 2.305|
|Cam Hole||.750, .749||.753, .756|
Notice the length is quite different, but that is not important. The distance to the Pin Hole is important and is fairly close.
Front Operating Pins
The reproductions are off in two important directions. The heads are too large in diameter to fit into the front brake operating shafts, both NOS and reproduction shafts. Nothing some carefull grinding can not fix. The heads fit into original wedges. The overall length is longer, but that is probably a good thing for those who are going to use a used wedge. You must keep the length issue in mind when assembling the brakes to be sure the lever is in the correct position for proper brake operation. Original worn pins I have found can be substantially worn the worst was .050" shorter. The 'best' worn pin was about .010 most were in the .020 to .030 range. I have two NOS pins and two reproduction pins.
To use the reproduction pins you must do some modifications. They are at an angle when installed so the point of contact on the head is not at the tip end. The head must be made smaller to fit the cups at each end. You must check that the shaft does not rub as the body of the repro pin is larger. I found they will rub some and need to be modified. I used the NOS rods because I had them.
|Length||7.240, 7.238||7.287, 7.287|
|Head Diameters||.386/.400, .396/.395||.410/.410, .410/.405|
Brake Shaft Bushings
I thought I would add this in here, later I will add some more details. Here is a picture of a NOS service brake shaft or emergency brake shaft bushing (they used the same part). From what I have learned they would have a steel or pot metal shell. Inside is a material like a woven brake lining that has a brass mesh and appears to have graphite on it. The material was inserted in the shell and the edges were crimped over to help hold it in place.