Rear Disc Brakes - Impala Tech
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post #1 of 2 (permalink) Old 07-07-2019, 06:40 PM Thread Starter
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Rear Disc Brakes

Why do you have to have rear disc brakes?

Simple everyone else has them and I can't live with out them.

But is this really true?

Ask yourself why are there disc brakes on the front? Easy because they are cheaper to produce; maximizing GM's profits. Has nothing to do with performance. If it were a performance issue, then there would be 14 inch discs up front like on a Corvette.

So why aren't there disc brakes on the rear axle? Once again it is cheaper to use drum brakes because of the requirement that a car have a mechanical (or completely independent hydraulic) emergency braking system. On the Corvette they put a miniature drum brake inside the hub of the rear rotor's hub. Totally inadequate, but it complies with the law.

Aside from the Corvette what other models have rear disc brakes?

The 1977-'78 Cadillac Seville ("Best of all it's Cadillac" in name only, it is actually a Nova which shares the same axle as a Camaro). Pay special attention when performing this exchange on the GM/Spicer 10 or 12-bolt axles, because the Seville rotors will not fit without having to machine the center hub of the rotor to fit the axle flange.

Because of the need to physically adjust these brakes constantly to compensate for wear the 1979 Seville used the same disc brakes as the 1970-'81 Firebird (can't expect a Cadillac owner to maintain their car). As far as that goes the 1977 and 1978 full size body Cadillac De Ville, and Fleetwood (as well as the Buick Riviera) used different calipers and mounting brackets, but the axles and rotors will bolt up to an AAW corporate 8.5 inch ten bolt rear end).

Then there were the RPO JL8 optioned 1968-'69 Camaros with special rear disc brakes (RPO J56 was the special front disc brake option) These were four piston fixed bridge designed by Girdling to stop aircraft on landing during WWII. These brakes are similar to the Corvette versions and bolt up to your Spicer twelve bolt rear. These were a very rare option but most parts do exist, and can be recreated from the aftermarket sources.

Additionally the RPO WS6 Firebirds from 1970-'81 had rear disk brakes but used a twin piston fixed bridge caliper with a separate lever activated emergency braking system (which unlike the 'vette actually works as a brake for more than just parking your car on hill). This is the most popular of the GM disc brake swaps, as it fits all 10-bolt and 12-bolt rear ends. All of these rears used the four-bolt axle flange measuring 3 1/8 inches across the top and 2 5/8 inches across the bottom.

The third gen Z IROC had rear disc brakes. made by PBR and those bolt up to the 8.5 inch ten bolt (though the Camaro used a smaller 7.5 inch). PBR also made the rear discs for the forth gen Camaro (1993-'97), and Brembo makes the brakes used today on Camaros and Corvettes. All of which will work if you can find a caliper bracket to bolt them to the flange, or you have to fabricate one for yourself that is strong and positions the caliper centered on the rotor(of course there are kits which sell stock GM parts with a custom made bracket).

All of these calipers from the above models had the driver's side caliper mounted to the front of the axle, and the passenger-side caliper is mounted to the rear of the axle. This is normal and was done to clear the rear shocks on most smaller cars (full size cars differed).

These are the brakes offered by GM (excluding front wheel vehicles that had a solid spindle on an I-beam on the rear: they used front disc brakes with a special mounting bracket). Now if you have a nine inch aftermarket Ford rear obviouly you will be looking to FOMOCO vehicles for your brake choices (and there are just as many to chose from).

So any of the cheap to middle priced rear disc brake kits you buy will be by somebody with a catalog of brake parts puting the cheapest off shore sourced car parts that he can find in box to sell you a rear disc brake kit (for the cheap kits any way) Middle priced still rely upon GM parts and possibly a custom caliper bracket, but they use better made Mexixan or Canadian made parts.

You can by pass the middle man and buy the parts (but not the mounting bracket; those come out of a junk yard) for yourself at Rock Auto dot com). OR they will make everything in house by themselves; such as Baer or Wilwood.



Big Dave

Last edited by Big Dave; 07-07-2019 at 06:56 PM.
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post #2 of 2 (permalink) Old 07-08-2019, 01:48 PM
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Join Date: Jun 2014
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Ok, couple of things that I keep seeing on this site that are not true.

Disc brakes are NOT cheaper to produce, as a matter of fact the only negative thing about disc brakes is the price.
Disc brakes provide better stopping and are safer.

In today's world drum brakes are used on the rear of the car when a manufacturer tries to cut down on cost and purchase price, meaning they are cheaper to produce. All other things being equal, a car with disc brakes on all four wheels will cost more than one with disc brakes on the front wheels and drum brakes on the rear. Their lower price also makes drum brakes more affordable to maintain.

Disc brakes are on the front because they are safer and improve braking. Unlike drum brakes, which allow heat to build up inside the drum during heavy braking, the rotor used in disc brakes is fully exposed to outside air. This exposure works to constantly cool the rotor, greatly reducing its tendency to overheat or cause fading. Disc brakes are much safer and improve braking, especially on a heavy car like an Impala, they are also less likely to lock up.

I agree that drum brakes are perfectly fine for the rear. Between 60 and 90 percent of a vehicle's stopping power comes from the front wheels, decent drum brake setup is all that's required for most rear wheel brake duty.

Last edited by 67SS; 07-08-2019 at 04:47 PM.
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