Mustang FAQ and How To's

Front Drum to Disc Brake Conversion for Classic Mustangs

Information provided by: Rick Larson

Introduction

Converting 4-wheel drum brake Mustangs to front disc brakes is a popular and effective way to increase the braking power of older Mustangs (and other Ford and Mercury automobiles).

What makes this swap attractive is the fact that the entire spindle and brake assemblies (but not necessarily the individual parts) of many 1960's and 1970's Ford, Lincoln, and Mercury autos are directly interchangeable. Since factory parts are used, the cost is reasonable and everything needed is available from your local junk yard and auto parts store.

Scope

The scope of this document is converting a manual 4-wheel drum Classic Mustang to front disc brakes. Converting to power brakes and all those issues (pedal pivot location, master cylinder, feel, ...) are not covered here. Classic Mustangs are defined as Mustangs made between 1964.5 through 1973.

Parts

The following list of parts are needed for the conversion:

Spindles
rotors
calipers
outer tie-rod ends
master cylinder
proportioning valve
miscellaneous parts

Spindles

Various spindles can be used to replace the front drums.

Mustang Spindles

Mustang spindles can be grouped into the following: 64.5-67, 68-69, 70-73. The early ones have the advantage to be concours correct, while the latter ones are stronger.

68-69 spindles are larger than the earlier ones but retain the same outer tie rod tapers.

The 70-73 spindles are much stronger than the other years and are the best to use for the conversion. However, the spindle went to a size larger tie rod taper so tie rod ends from a 70-73 must be used.

The Boss 302 Chassis Modification booklet (a reprint of the 1970 factory booklet showing parts and methods for beefing up the Boss Mustang for better handling) recommends a '69 F250 2 wheel drive, power front disc brake MC and Calvin Sanders, has successfully used this in several Mustangs.

The MC from a 76 6-cylinder Granada bolts right in and works. Other Granada master cylinders also fit. I suggest if you use a donor Granada for the spindles/rotors/calipers, get the master cylinder. You may be able to use a power MC with some push rod modifications (a power MC has a much shallower rod hole).

May 1995 issue of Mustang Illustrated lists several compatible MCs.
Raybestos # MC39037 (RH) cast iron 7/8 bore 78-81 Ford Fairmont,Granada,Futura,Zephyer(Merc)
Raybestos #MC39531 (RH) alum 21mm 81-86 Tbird, 82-86 Mustang, 83-86 Marquis (Merc)
Raybestos #MC 39310 (RH) cast iron 7/8 bore 81-83 Escort, Explorer, lynx, Mark VII (Linc)
Raybestos #MC 39027 (LH) cast iron 7/8 bore (LH) 76- 80 GM Monza, SkyHAwk,Starfire,SunBird
The article has a wealth of tips and advice regarding interchangebility and compatibility and fitting. However, please note which side you want the plumbing on before you pick a MC. IMHO, you should get a left hand side MC.

If you have a 1964-1966 model year car with a single reservoir master cylinder, you should consider upgrading to a later style dual reservoir master cylinder for safety reasons even if you don't want to add front discs.

Proportioning Valve

Get either the stock one from the donor car or an adjustable one from Summit. The adjustable one allows changing the brake bias. Some people like this, others (like me) use the stock one.

Tie Rod Ends

Depending one what spindle you choose, you may need to get new tie rod ends. When upgrading with either 70-73 Mustang or Granada spindle, get the tie rod end to fit. Also, tie rod adjusting sleeves may been needed. Original sleeves on a '66 will not work with Granada tie rod ends. However, Granada sleeves will thread on the Mustang inner tie rods.

Miscellaneous

Depending on what spindle/rotor/caliper choice, you may need different brake hoses.

When I replaced my drums with the Granada parts, I needed new hoses. Granada hoses will not mate to the hard lines. I ended up with hoses from a '73 Mustang. I also replaced the hard lines and extended the lines to help locate the brake hoses around the suspension. I swapped the hose/hard line bracket (left went on the right side, right went on the left side) and turned them counter clockwise 90 degrees.

Issues

Now that you have larger disc brakes, your old 14" wheels may not fit any more. Mustang owners have had problems with 14" disc-type styled steel wheels, 14x6 Torq Thrusts style wheels clearing the calipers of the new set up.

Be sure to measure this before you make the decision. I had to get Granada rims to fit over the new disc brakes. The center hole on the original 14" wheels is smaller than the new rotor.