Technical 1940 Ford truck disc / bendix drum conversion and keep stock Ford wheels how to

I did a lot of research and reading on the forums here and found some good info and also found a lot of unanswered questions, so here is a writeup on a disc/drum conversion I did on this 1940 Ford. I wanted to have disc brakes in front and self adjusting Bendix drums in the rear and keep the stock Ford drum brake rims. I got the front disc kit and rear drum kit from Speedway. Now when you order these from Speedway they tell you that you cannot use stock Ford drum brake rims for this setup. Which is true, if you put the stock rims on they will hit the caliper because the inside of the rim goes at an angle from the mounting surface. What I found out is that when you put this disc brake kit on it moves the mounting face 3/4" inward from where the drum was, so this changes the wheel backspacing which allows you to add a 1/4" wheel spacer and mount the stock Ford rim with enough clearance for the caliper and keep your tire in the right spot inside the fender with no rubbing when turning. It was all bolt on with only one modification. I had to clearance the caliper bracket to clear the turn stop stud, you can see it in the pics. I also had to get adapters to go from the end of the flexible brake hose to the stock hard lines on the truck, they were different sizes. The rear Bendix drum brakes were simple and bolted right up and they use the stock drums. There is a choice between 1.5" and 2" rear drums which refer to the width of the brake shoes. I went with the 2" because the 1.5" were on backorder. I had to clearance the inside of the drums to make room for the wider shoes. While I had the rear drums off I had them turned for a nice new surface and also repacked the bearings and put a new axle seals in. The existing parking brake cables hook right up to these and work good. I used all the existing hardlines and replaced the master cylinder with a 1970 GMC truck disc/drum unit with a 1-1/8" bore. It is a 2 bolt master so I had to get a 2 to 3 bolt adapter plate, I got the adapter and master from Summit Racing. I had to also cut about 3/8" off the brake assembly pushrod so I had some adjustment left in it, the new master does not have a hollow piston like the stock one. Before you install the master cylinder you have to clearance the frame for the rear brake line and also cut a larger hole in the floor to access the top of the master cylinder. I just made a new cover plate out of aluminum and used self tapping screws to hold it down. Once the master cylinder is mounted I just rebent the existing lines and hooked them up. I used a mechanical brake light switch on the pedal instead of using a pressure switch, which is just my preference, you could easily add one inline on the tubing. So now that the system is all put together I used a vacuum bleeder and pulled fluid through the system then did the 2 man pump/bleed method to get a good pedal feel. I decided not to use residual valves or proportioning valves in this setup and it works great, no problem stopping this truck at all. Always have plenty of brake, they stop evenly without pulling right or left and I can lock them up if I choose to. I had about $1100 and 10 hours in this job. Look in the pictures below, I have pics of the invoices showing the part numbers. Hope this helps anyone looking to do this conversion.

 

thanks for sharing......

 

That's a great writeup and good descriptive pictures. I have been contemplating the same thing but have always been put off when they say you can't use the stock wheels. Now I get it. They also claim that you can't use this system if you have cut off the steering arms and replaced them with the bolt on type. I can see why from your pictures. I will have to think some more on that because I have the bolt on steering arms. Thanks for your work. I am saving it.

 

Slick setup. I'm going F=1 brakes on the front of my A but that is something to keep in mind if it doesn't stop well enough.
I'm kind of screwed because I am going to have to change to bolt on steering arms because the chrome spindles I have have welded on dropped steering arms that most likely won't pass inspection.

 

Thanks for sharing this! Even I can understand it.
Had planned this for my stalled pickup project.

 

This was a pretty cool build. Has a 57 T-Bird engine with fenderwell headers mated up to a Borg Warner T85 with a custom tailshaft to mate up with a Columbia 2 speed rear axle.