46-48 Plymouth P15 Disc Brake Conversion

46-48 PLYMOUTH P-15
Plymouth P15 Disc Brake Conversion

As printed in: TEX SMITH's
HOW TO BUILD CHRYSLER/PLYMOUTH/DODGE HOT RODS

DISC BRAKE CONVERSION

Early Chrysler products suffer from very poor original drum brakes. Trying to adapt disc brakes has been
a major problem until this solution came along. On MoPar products of the '50's and later, it is possible
to swap spindles from newer MoPars that have discs.

by Ed Gross

When I was putting together my 440-powered '48 Plymouth sedan together, I recognized that the front brakes, which needed to be rebuilt, would be inadequate. When looking at the available kits for this model, you better have deep pockets because the only kit I found was $650 plus. So, the only other answer was to be creative (also known as cheap). When my brother-in-law offered to give me the backing plates, rotors and caliphers from his early '70's Blazer, I couldn't pass them up. But these units, proved to be too massive to fit inside of 15" wheels. So, it was back to the drawing board.

By looking around an auto recycling center (junkyard), I found that the '79-'85 (11") Oldsmobile Tornado used a front rotor that does not have a hub attached. I believe the same rotor is used on the front of Eldorados and front and rear of Rivieras.

ROTOR/HUB
Originally, I planned to have the '48 Plymouth hub machined to fit inside the rotor, but it fit without any machining. To attach the rotor to the hub, I first removed the brake drum form the hub and used it as a drilling template for the 29/64" holes in the rotor. NOTE: There's enough material for at least two attempts to get it right. Tap the rotor for 1/2"-20UNF full thead studs. Next, the hub is drilled for the 1/2" clearance holes to allow the studs to pass through and attach to the rotor. I assembled the hubs and rotors and then had the rotors turned. NOTE: It may be necessary to disassemble the hubs and rotors and shim them to make up for any imperfections.

CALIPHER MOUNTING PLATES
The backing plates I used came from the early Blazer 4-wheel drive. They're made of formed 1/4" plate and could adapt to other applications. It was easy to for them to the three mounting bosses on the spindle. NOTE: I cut loose the mounting tabs from the backing plates.

Alignment was made on the center, and three 9/16" holes were drilled in the backing plates. I then attached the caliphers (wit new brake pads) and slid them over the rotors. After straightening and trimming the mounting ears, I tack welded them in position. Theh were removed and finish welded on the bench.

Final assembly was made with new wheel bearings, oil seals and hoses. You can have custom hoses made or look through the cross reference books for a car using the same calipher for a hose that is less bulky than the Balzer's. You will only be able to use 15" wheels intended for use on disc brake cars.

If you have questions about this car or project, contact Ed Gross @ e-mail: egross@wi.rr.com

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