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Old 05-03-2007, 03:38 PM   #1 (permalink)
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Question Disc Brake Conversion

I know that lots of people go the, "heavily sought after 1979 Cadillac Eldorado caliper with the e-brake", way, but what about the 1978 Eldorado caliper with the bigger piston. Has anyone done this conversion and how did it turn out?
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Old 05-03-2007, 04:42 PM   #2 (permalink)
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The question would be why would you use the larger piston? Of course, the correct answere is "my truck needs bigger brakes". If it doesn't, you'll find your rear end locking up before the fronts. From time-to-time, I've seen posts that claim they used the full-size front calipers (bigger bore) on the rear of there trucks; however, they never discuss how well it all works. Seems most try to avoid the calipers with the built-in parking brake. Bottom line, is you need to asses your brake needs based on truck weight, tire size, etc. I run Chevy truck fronts (2.94 bore) and '79-86 Cadillac rears, with e-brake, (2.12 bore). My jeep weighs ~4200 LBS, and I'm running 33" tires. My braking is fairly well balanced, without a proportioning valve; I can lock them up on dry pavement. If I installed the 2.5 bore '78's, I'm sure I'd be "over braked" in the rear.
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Old 05-03-2007, 07:17 PM   #3 (permalink)
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Quote:
Originally Posted by Bubba_Jeep View Post
The question would be why would you use the larger piston? Of course, the correct answere is "my truck needs bigger brakes". If it doesn't, you'll find your rear end locking up before the fronts. From time-to-time, I've seen posts that claim they used the full-size front calipers (bigger bore) on the rear of there trucks; however, they never discuss how well it all works. Seems most try to avoid the calipers with the built-in parking brake. Bottom line, is you need to asses your brake needs based on truck weight, tire size, etc. I run Chevy truck fronts (2.94 bore) and '79-86 Cadillac rears, with e-brake, (2.12 bore). My jeep weighs ~4200 LBS, and I'm running 33" tires. My braking is fairly well balanced, without a proportioning valve; I can lock them up on dry pavement. If I installed the 2.5 bore '78's, I'm sure I'd be "over braked" in the rear.
I'm running a CJ7 with a 360 and 35" tires and will probably go to 36's or 37's soon. Also have a Frod 9" rear w/4:10's, locked and a D44 front, locked. I'm not sure of weight. Think there's a chance I'll be over braked with the larger '78' Cadillac rear calipers as opposed to using the smaller '79' ones? I have no proportioning valve as of yet, but I did swap out the stock master cylinder for a disc to disc one out of a '79' Corvette.
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Old 05-03-2007, 07:38 PM   #4 (permalink)
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Quote:
Originally Posted by Bubba_Jeep View Post
The question would be why would you use the larger piston? Of course, the correct answere is "my truck needs bigger brakes". If it doesn't, you'll find your rear end locking up before the fronts. From time-to-time, I've seen posts that claim they used the full-size front calipers (bigger bore) on the rear of there trucks; however, they never discuss how well it all works. Seems most try to avoid the calipers with the built-in parking brake. Bottom line, is you need to asses your brake needs based on truck weight, tire size, etc. I run Chevy truck fronts (2.94 bore) and '79-86 Cadillac rears, with e-brake, (2.12 bore). My jeep weighs ~4200 LBS, and I'm running 33" tires. My braking is fairly well balanced, without a proportioning valve; I can lock them up on dry pavement. If I installed the 2.5 bore '78's, I'm sure I'd be "over braked" in the rear.

Bubba your Jeep has got to be a bullet proof rocket other than the dana 44's but they are plenty strong enough for 33's. Is it a DD?
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Old 05-03-2007, 08:07 PM   #5 (permalink)
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Shredit73, your CJ probably weighs as much as my XJ, since you started with a heavier frame, and I had add "reinforcements" I'm not sure what to say about being over braked. Worse case, you'll need to install a proportioning valve in the rear circuit. I bought my rear D44 with the Caddy metric calipers. If I were to have done it myself, as I would now, I can't say I wouldn't have opted for the larger calipers. With regard to the e-brake set-up, the Caddy systems are a bear to bleed and set up right; however, I dont really know of a better alternative, if you want an e-brake.
Broke_ass_yj. It used to be a daily driver, but it's not fun any more, especially after I put together my own rear leaf pack. I got a solid 6" lift, but the rear spring rate is way too stiff, relative to the front coils. Plan on changing that sometime soon.
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Old 05-03-2007, 08:46 PM   #6 (permalink)
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As said above, the GM Dana 44 Calipers are 2 15/16" and the intermediate GM calipers (AKA S-10 Blazers, Monte Carlo, Camaro, Caprice,etc) with 5.5" bolt spacing are 2 1/8" bore. When you start equilizing bore sizes front and rear you run into a situation where an adjustable proportioning valve won't stop the rears locking up. You end up having to run two or more valves to knock the pressure down.

My advice is to use the GM intermediate caliper with a 1" thick rotor and your brakes will be close with that. This is what I run on the GPW and Bronco and it works well and only needed a few turns of a $30 proportioning valve from Summit.
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