Rear Disc Brake Conversion

[Manta22]

Like all drum brakes, the Corvair rear drum left a lot to be desired so it is recommended to convert the rear brakes to a disc setup.

Fortunately, the conversion is relatively easy (as most conversions go) if you stick to Chevy parts. After removing the brake drum, disconnecting the emergency brake cable and axle universal joints, the hubs were removed from the trailing arms. The drum backing plate and associated hardware was removed and the old wheel bearings were removed and replaced with new ones.

Since Chevrolet made no provision for re-lubricating these beings, I drilled a small hole through the hub into the bearing housing and tapped the opening for a 10-32 screw for sealing out dirt & water. To lubricate the bearings, I use a syringe and inject grease into the drilled hole. While the hubs are off it is a good time to remove the trailing arms and replace the rubber bushings. After 50 years, chance are that they are shot. New bushings will allow the rear suspension to be aligned properly and the improvement in handling will be immediately apparent. U-joints may need to be replaced as well; use "Heavy- Duty" joints.

I used brake rotors and calipers from a 1988 Corvette. The rotors simply slip on the Corvair hubs and brackets to mount the nice Australian- made Girlock aluminum calipers are easy to make. I cut out two pieces of aluminum plate and bolted them together with high grade bolts; this provides the proper offset for the calipers to fit over the rotors. A drawing is shown below. The '88 Corvette and some models of Pontiac Firebird use this caliper. It has a "pull" lever for a parking brake cable. This can be adapted to the original Manta parking brake cable without much trouble.

Check the original Ford Thunderbird brake proportioning valve. It may be full of rust and not functioning at all. Replace it and set it to about 50% as a starting point for adjusting the F & R bake percentage.