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GM Rear Drum to Disc Brake Swap

Stock Rear Brakes Giving You Fits? Stock rear brakes giving you fits? We show you how to get big brakes for 10- and 12- bolt axles.

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Junkyard Systems
As mentioned before, enterprising sorts may wish to build a rear disc system using junkyard parts. The old way of swapping out your drums to discs was to acquire the setup on an '80-'86 Cadillac Seville, a '79-'85 Cadillac eldorado, or a '79-'81 Firebird with the WS6 handling package. These cars were equipped with 111.2-inch rear brake rotors. The Caddy used a 5x5 bolt pattern, while the Firebirds were the conventional 5x43.4. So the hot ticket was to grab the calipers and brackets off a Caddy and the rotors from a Firebird. Those parts are still available. A recent trip to a local pickyour-part turned up at least eight complete sets of Seville brakes. The WS6 rotors are much harder to find in the 'yard.

Newer cars offer better systems, and late-model F-car swaps are becoming popular, especially the brakes from lS1 cars. These systems include PBR calipers on 12-inch rotors with a drum-inhat- style parking brake. The rotors are drilled with the common 5x43.4 bolt pattern, making this a popular swap for older musclecars. Good luck finding them in the junkyards, though. The parts are too desirable, so eBay will be your best bet for finding those setups. Also, these brakes will not fit behind most 15-inch wheels, so plan on bigger wheels if you're contemplating this swap.

Surprisingly, the biggest drawback of a junkyard system is cost. Brake parts operate in a harsh, dirty environment under extreme temperature ranges. Therefore, the parts can be totally clapped out by the time you pull them from the 'yard. While we embrace the practice of hosing off junkyard parts and putting them to use, we cannot advocate cutting corners with your braking system. So by the time you've overhauled the calipers, sliders, mounting brackets, dust boots, and parking brake cables, you may well have spent as much or more than it would have cost to buy an aftermarket kit.

What's A PBR Caliper?
PBR is an Australian company specializing in automotive and light-truck braking systems. The systems utilize a floating caliper supported by a caliper bracket that bolts to the spindle or axle flange. Their simple design and adaptability to accommodate a variety of rotor diameters by using taller caliper brackets make them a popular choice for both the manufacturers and aftermarket alike. PBR brakes were standard equipment of many performance cars including the Corvette, Camaro, Firebird, and Mustang SVT Cobra. In addition to calipers, PBR manufactures rotors, parking brake assemblies, and brake lines and hoses.

Measurements You Need To Know
GM used the same mounting flange for most of its 10- and 12-bolt rear axles with C-clip axle retainers. The flange bolts form a trapezoid shape measuring 31.8 inches across the top and 25.8 inches across the bottom. There are a few variations to watch for: Some station wagons, for example, may have a bigger flange. To be safe, take a measurement of your car and the potential donor's.

In addition, be sure to measure your wheel-stud bolt pattern, the pattern of the donor rotors, and the pilot hole in the center of the rotor because some axles have a bigger pilot than others.

Finally, be aware of possible interference of components. Cars with staggered shocks may need to mount the calipers in different clocking positions to avoid contacting the shocks during suspension travel.

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