Brake Upgrade Q's

[cycleguy55]

The type of braking system will depend upon how much track use you're planning and the speeds you'll be running (autocross vs road racing). I did a similar conversion on my car a year ago. When I bought it in 2014 it had the original 9.25" Mustang II discs on the front and 11" drum brakes on the 9" rear end and was just not going to work for me.

I used a 'universal' kit on the back that works for the various types of Ford 9" rear ends, and I believe it also fits the 8.8" axle. It comes with 3 sets of brackets to fit the different rear ends, and uses the GM 'large calipers' with integral parking brakes and 11" solid surface rotors. The only glitch on the installation was there was interference between the calipers and brackets and the rear sway bar and it's brackets. The solution was to rotate the brackets 180° on the axle ends and use the right caliper on the left and vice versa - this was necessary for keep the bleed screws on the top of the calipers.

The parking brake cables were a bit short, but I was able to extend the 5/16" NF threaded rod on the parking brake lever to engage the cables. It was about 1.5" too short, so I used a section of 5/16" NF bolt plus a coupler I made from some steel tubing - a few minutes of threading it with a tap and it was ready for use. Be aware that you need to use the parking brake regularly on the GM calipers to keep them properly adjusted.

On my MII front end I went with a Wilwood 4 piston setup with 11" solid surface rotors. You will need braided lines to connect to your existing plumbing, plus adapters at both ends (1/8" NPTM to AN -3 for calipers, 3/8" x 24 TPIF to AN -3 adapters with clip groove for hard line connection).

I had a combination valve in the brake system (distribution plus proportioning valve for the rear brakes). I removed the proportioning valve mechanism from the combination valve and installed a manually adjustable proportioning valve in the rear brake lines but, to date, have found no need to dial back the rear brakes. I guess the combination of the GM calipers and wider tires on the rear works well with the 4 piston Wilwood calipers in front, but the adjustable valve is there should I ever need it.

I put speed bleeders in all of the calipers - highly recommended. The Wilwoods have 4 bleed screws, but you only need speed bleeders in the upper pair on each caliper. It took a while to bleed the brakes, especially the rear ones, as I pretty much drained all the brake fluid from the system.

The first few stops on new rotors all around were a bit scary as there is little braking power until you start getting them bedded in. It took 2 or 3 light applications of the brakes before I could feel the brakes getting progressively stronger. Once the bedding process was done it was obvious the new brakes were MUCH stronger than the old brakes. I'm really happy with the results - much better than the old system and well worth the investment.