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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
The braking system on the 1960s Mustang is certainly adequate as long as the car is equipped with power discs on the front. We looked to improve braking performance further, and make it bulletproof even on a track day. However, on a car like an original Hi-Po '66 fastback, a '68 Shelby GT350, or a '69 Boss 302, you may want to maintain some sort of vintage appearance rather than bolt up a set of monster billet aluminum calipers and rotors. This is of even greater concern when these modifications require cutting and welding to such a rare Pony.
Our test mule for this article is out of the Christiana Muscle Cars (New Castle, Delaware) stable-a real '69 Boss 302 Mustang. The Boss is similar to the rest of the 1960s Mustangs with 11-inch power disc brakes, and 10x2-inch drums in the rear. The only real difference is that the Boss came with 15-inch wheels, which are required for this brake swap.
Having driven this '69 Boss 302 at a bunch of open track events and drag races, we knew that the braking distance was not only related to the brake system performance, but the overall grip of the tires on the car. So before we did any brake distance testing, we called up our guys at BFGoodrich and ordered up a new set of their P245/60R15 BFG Radial T/As.
The big brake kit we are going after was created in the late 1968, early 1969 seasons of the Trans-Am road racing championship. The front calipers and rotors are off of a big Ford like a Thunderbird or LTD. These binders feature massive four-piston calipers originally made by Kelsey-Hayes. The race teams fabricated a custom bracket to adapt the calipers to a Mustang spindle. You can almost see Bud Moore doing a brake job on his grandma's Ford LTD and thinking, "We should use those brakes on the Trans-Am Mustang."
The front brake setup is really a conglomeration of parts. The foundation is a '70 Mustang drum brake spindle, which has a larger stub which uses a larger bearing than a disc brake spindle. Also, the hub is a disc brake piece off of any disc brake Mustang. The calipers and rotors are right off the shelf in the parts store, along with the brake pads, which are from a '66 Ford Thunderbird. The tricky part is the caliper bracket, which is a custom-made piece. Lastly, the rotor is a larger 12-inch diameter-one full inch bigger than stock. This complete front brake kit, which includes everything you need from spindles to steel-braided brake hoses, can be purchased from Christiana Muscle Cars for $2,450.
The installation of the front brake kit requires you to get a little dirty and involves a couple of steps. First up is the dirty job-packing the bearings and installing the grease seals on the hub. The tricky part involves the '70 drum brake spindle, which is slightly different than our '69 Boss spindle and will require a frontend alignment when all is said and done. We took this as an opportunity to go for an aggressive street/open track alignment. We added a bit of caster and went with a 1/2 degree of negative camber, which helps with stability when turning into corners. This was definitely an improvement.