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1969 Ford Mustang Boss 302 Trans-Am Brake Swap - MMF Tech
Upgrading Your Classic Colt With Vintage Trans-Am Hi-Po parts
Just like the front setup, the rear brakes were sourced from a larger Ford car, such as a Torino. In the later 1960s, the Trans-Am teams switched to a disc brake setup in the back, but that required welding on the rearend. This is taboo in our theme of keeping a classic Mustang intact with no cutting, welding, or adding of modern-looking parts. So, we called Master Power Brakes for its big drum brake kit (PN DR 1504K), which retails for $495. This kit comes with huge 11x2-inch rear drums with cooling fins. This is 1 inch larger in diameter over the stock setup in all '60s Mustangs. The kit increases the size of the brake shoes and the drums. The larger drums do add weight, but the added surface area helps to disperse more heat, and the fins help keep the drum cool from warping under excessive braking that you would experience after a day at the track. This will decrease brake fade and give the driver more confidence.
The kit is preassembled with the backing plates, shoes, springs, and wheel cylinders. It almost bolts itself onto the car...well almost. The installation is pretty straightforward. The toughest part is getting the parking brake cables off the old backing plates and hooked onto the new setup.
Since we were replacing the stock brake setup on the entire car, we went ahead and contacted Classic Tube and installed a complete stainless steel brake line kit, including its trick new steel-braided Stop Flex brake hoses-our one concession to the modern era. This is also the perfect time to change the brake fluid. Most people never think about changing their brake fluid, but the fluid traps moisture and will quickly cause the brake fluid to boil and fail under extreme situations. If you plan on taking your car to a track day, many times the track will require you to have changed your brake fluid within the past year. Christiana Muscle Cars recommends using regular DOT 3 brake fluid, as it believes that synthetic brake fluid does not last as long in the system before it turns color and begins to damage the internal brake parts.
Now is the time to call your buddy with a strong right leg and bleed these massive brakes. It takes more than a few pumps just to get fluid out of the front calipers because they hold a ton of fluid. Once all four corners are bled and all the lines and bolts are double checked, cautiously take the car for a testdrive. Take your time and be careful with newly installed brakes. A simple bolt that is not tight or a line that is a bit loose can cause you to lose your brakes and get into an accident-not good. Be sure to give them a few good pumps once you start the engine and before you roll out of the driveway.
The stock baseline test was done at Atco Raceway in New Jersey on a sunny 81-degree day. As we all know, classic Mustangs do not have antilock brakes. This becomes increasingly apparent when measuring the stopping results. Once the tires lock up, it can be like hitting a patch of ice. The car seems to take off and just blow right by the desired stopping point. So, car control and brake pedal management is increasingly important even with the new brake setup. We averaged the best two runs on the stock setup and came away with a 60-0 mph stopping distance of 139 feet.
After the brake upgrade, we had the frontend aligned and took a couple of easy testdrives before heading to New Jersey Motorsports Park in Millville, New Jersey, for an open track weekend. The final brake test came about a month later and the air temperature was only 70 degrees, with cloudy skies. This is not a big swing in conditions, but the pavement temperature was considerably cooler, which often reduces grip.