rear disk conversion

[CJJ67]

This is my first post, but i've managed to keep my truck running thanks to the experts on this board. I converted my 67 to front disk brakes but my question is what about the rear? I read somewhere that you can use the stock brackets from a 77-79 cady deville. Can I use the stock brackets from a 79-81 eldorado. These type cars I can find. If not, what other type vehicle should I try. I really want to thank all the experts who freely share their knowledge. My wife thinks I'm a genius.

[screamin_c102]

Converting to rear disk is something I looked into long and hard and decided not to do it. Hooking up a set of calipers and finding a set of rotors is the easy part, correctly biasing your brake system is another completely different problem that can be expensive to do properly. Properly installing an emergency brake in the rear is also another hurdle to overcome.

It can be done ghetto style for a couple hundred bucks, but if you want to do it right and have a completely functioning and properly operating system then it gets pricey.
I know there are adjustable proportioning valves available and thats fine if you never load your truck or adjust the bias everytime you drive with a different load. But again this is a truck where the rear end is very light and can easily go into a rear end slide.

Can anybody say 360s on a wet stretch of Oregon freeway after a Ferd has cut you off, I can.



Something to chew on: The manufacturer didn't offer 4 wheel disk until after they had perfected anti-lock brakes (ABS) this is because the weight of the rear of a truck can vary several hundred pounds depending on the load it is carrying, unlike cars which stay relatively constant. In order to properly bias a trucks brakes you would have to figure out a way of controlling the rear wheel lock-up threshold under all of these load conditions as well as varying road conditions. The ABS system does this and made the switch to 4 wheel disk a no-brainer for GM.

Without a computer or automated control system it seems to me that retro fitting a fully functioning system is unadvisable.

Just my $.02

[krue]

Welcome to the board from South Mississippi! What I want to know is how did you go this long without posting?

[john]

Heres an article about cad or chev parts. Also I think 9" lincoln diffs have been used. John


http://www.classicperform.com/tech_a...kes-trucks.htm

[68w/sbc406]

Originally Posted by screamin_c10

Can anybody say 360s on a wet stretch of Oregon freeway after a Ferd has cut you off, I can.

no but 180 after getting cut off and then slammed by a %$#&ing jetta on a wet portland road

[screamin_c102]

Originally Posted by 68w/sbc406

no but 180 after getting cut off and then slammed by a %$#&ing jetta on a wet portland road

Ya gotta luv living between California and Washington, It's like Nascar every damn day.

"He didn't hit ya he rubbed ya, and rubbin' is racin son"

[68w/sbc406]

Originally Posted by screamin_c10

Ya gotta luv living between California and Washington, It's like Nascar every damn day.

"He didn't hit ya he rubbed ya, and rubbin' is racin son"

yeah the californians drive like Tony Stewart and the washingtonians drive like DW before he retired

[roj2323]

here's what i'm going to go with:

http://www.steeltechsolutions.com/RE...PAGE_CODE.html
the brackets are $89 and use the same rotors and calapers as everyone elses. i figure why buy a kit when i can build one by going to carquest or autozone for half the price.

ondrew

[70short/step]

Originally Posted by 68w/sbc406

yeah the californians drive like Tony Stewart and the washingtonians drive like DW before he retired

You say "Drivin like Tony Stewart" like its a Bad thing!!

[Rod]

Welcome and here's some info and links.


Haven't looked up how this swap works in a while but its Cadillac Seville maybe 77-79 era parts you want as it give you an emergency brake cable option that way also.

Anyway I had some of these swap pages book marked and there still good..so happy reading. one says use seville the other for cars says use deville..so whatever works.

There are kits, but hey, I like scronging around a little.


http://www.geocities.com/motorcity/6765/page11.html

http://home.pacbell.net/bigiron/Arti...rRearDisc.html

[BobbyK]

Here's a parts list for when I did my rear disc brake swap onto my 71 Blazer.

Master cylinder-1978 Corvette
Napa part # UBP39052
non-napa part#m82071
$81.49,no core charge

Dual diaphram booster(no really needed but I put one on)
Napa part# 5471007-$113.99
$4.00 core charge.

TSM rear brake kit.
Includes rear disc mounting brackets,redrilled rotors and short rubber brake lines.
Part# 2531
$239.95
Stainless flexable lines are available for $50.00 extra
part # 3702-8

Rear disc brake calipers with integral emergancy parking brake for a 1984 Cadillac Eldorado
Auto Zone part # C243 and C242(remanafactured)
$39.99 each with $80.00 core charge.

Proportioning valve-
1984 Cadillac Eldorado
Obtained from auto wrecker for less than $10.00(free if you stick it in your pocket)

[DTerry]

Hey screamin, what's up... (DTerry's dad again)

I don't disagree with your post, in fact for a long time I kinda thought the same way. But then I got thinking about the fact that there are drums in the back - and that doesn't cause problems. The drums don't have any sort of load compensating device. There is a proportioning valve on both disc and drum setups, and I realize those valves are different for each. They both just proportion the pressure allocated to the rear. So what gives? There must be something I'm missing.

I can tell you that on our race car, where we know the exact weights, and test brake bais regularly, it (rear discs) makes a huge difference (good thing). We have an adjustable bias controller. I'm not saying that the controller we have is good on the street (and would not recommend one - too dangerous)

My thought is that until the manufactures came up with anti-lock or load compensators (chevy, maybe others) everyone just lived with the fact that trucks had brake issues with load variations.

Thoughts anyone?

[junkyardjohn]

I'VE GOT A 9 INCH OUT OF A 75 MK4. I HAVEN'T PUT IT IN MY 71 SHORT FLEET PROJECT, BUT IT SURE LOOKS LIKE THE SETUP. IT'S WITHIN AN INCH OVERALL OF THE CORRECT LENGTH, & HAS 5 ON 5 AXELS, SO IT TAKES THE SAME SIZE BOLT PATTERN AS THE WHEELS ON OUR OLD TRUCK. IT HAS A LEVER ON THE CALIPER FOR THE E-BRAKE. I SWAPPED SOME PARTS TO A BUDDY THAT OWNS A DRIVELINE SHOP FOR A COMPLETE REBUILD & A POSI CENTER SECTION.
SCEAMIN_C10.....THIS IS THE FIRST TIME I'VE EVER HEARD OF ANYONE EVER SAYING THAT DRUMS WERE BETTER. I'VE HEARD ALOT OF PEOPLE SAYING THAT THERE DRUMS WERE GOOD ENOUGH (ALSO ) BUT NEVER BETTER THAN DISCS. I GUESS EVERYONE IS ENTITLED TO THERE OWN OPINION, BUT UNTILL YOU CAN EXPLAIN HOW ALL OF THESE PROBLEM AFFECT DISCS & NOT DRUMS, I THINK I'LL HAVE TO CALL B/S. PLEASE ENLIGHTEN ME. JOHN

[Low69CST]

Here is my setup. I took the entire rear out of an old Imperial with rear discs. There rear end is one hefty peice. Draw backs are I had to redrill the axles for the truck bolt pattern, weld on saddles, and the rotors and parking brake parts are discontinued. Didn't know that till after I bought it, but i've got good stuff now, so I should be alright. I originally went that route to have rear discs and have something that I could get parts for at any auto parts place. If I did this over again, i'd use a Lincoln rear end, cuz they have discs, 5 on 5 pattern, closer to same width, and you order a stump built however you want and bolt it straight in. Live and learn.

What is meant by load variations? You mean haulin stuff? What difference does disc or drum make? Friction is friction. If the rear is set so they don't lock up unloaded, then any additional load on the rear would give the tires more bite and you should be able to apply more pedel pressure without them locking. Whenever you haul anything they brake, steer, and handle different, so you adjust with your driving right?

[shifty]

Anyone have a picture showing how the brake lines are run naturally in the rear for one of our trucks? It looks like BobbyK welded some brackets to hold the lines in his. I don't know if I would be comfortable doing the same with mine knowing it's so close to the u-bolts and my truck is going to be so low to the ground.

[DTerry]

Originally Posted by Low69CST

What is meant by load variations? You mean haulin stuff? What difference does disc or drum make? Friction is friction. If the rear is set so they don't lock up unloaded, then any additional load on the rear would give the tires more bite and you should be able to apply more pedel pressure without them locking. Whenever you haul anything they brake, steer, and handle different, so you adjust with your driving right?

Yes, load variations = haulin' stuff. And you're right - for the most part. Later chevy (and possibly others) trucks came with this load sensing device that was installed bewteen the rear axle and the bed. It basically measured this distance and did some sort of rear brake porportioning. The idea being that with more weight in the truck you could supply more force (via fluid) to the rear brakes and thus increase your total stopping power. This attemped to adjust the vehicle so that the driving style wouldn't need to (adjust).

I don't know how other newer trucks did it (excluding anti-lock).

In my opinion, disk brakes work a whole lot better, and if you install the correct proportioning valve, it's a good idea. The catch here is "the correct proportioning valve" because nobody ever made one for trucks without some sort of antilock or load compesation device. You'll need to do some research to find one close to what you need (depends on what the parts came from).

I think that screamin_c10 is absolutely correct in his statement on this, and you should consider his advice. But if you don't plan on hauling alot, or you're confident you can adjust your driving style, or you can find a proportioning valve (maybe adjustable - I don't advise it) that works... go for it.

One last thing, unless I'm miss interpreting something, nobody said that drums are better than disc's.

[LONGHAIR]

I will....... with a few qualifications "drums are better than discs". As far as pedal effort to braking power drums are better. Discs are the reason that power boosters were added. It take far more line pressure to operate disc brakes. Drums are "self-energizing", so the pedal pressure doesn't have to increase as much to shorten stopping distance. It is kind of like a snowball rolling down a hill.........it takes less additional pressure to increase stopping power.
Drums don't have the fading with heat problems or the wet performance problems of discs either. Look at dump trucks and semi trucks/trailers.

The real advantage of disc brakes has to do with the lazy and mechanically inept average driver. They are far more forgiving as far as adjustment and mechanically simpler. Disc brakes were first used in the front of cars to combat the "pulling during braking" that improperly adjusted drums can cause.

Personally I am not sold on the concept of discs on the rear....especially if you are expecting better stopping. They may look great...if that is all you are looking for. I'm not saying don't do it, it can be done, and done safely...just don't expect a great difference in stopping power. Discs will clean better on a 4x4 but they will act odd (slippery) when the are wet.

I do remember working on many mid/late 80's trucks with the self adjusting rear proportioning valve. The main thing about it at the time is that it had to be adressed when lifting 4x4s.

[junkyardjohn]

Originally Posted by LONGHAIR

I will....... with a few qualifications "drums are better than discs". As far as pedal effort to braking power drums are better. Discs are the reason that power boosters were added. It take far more line pressure to operate disc brakes. Drums are "self-energizing", so the pedal pressure doesn't have to increase as much to shorten stopping distance. It is kind of like a snowball rolling down a hill.........it takes less additional pressure to increase stopping power.
Drums don't have the fading with heat problems or the wet performance problems of discs either. Look at dump trucks and semi trucks/trailers.

The real advantage of disc brakes has to do with the lazy and mechanically inept average driver. They are far more forgiving as far as adjustment and mechanically simpler. Disc brakes were first used in the front of cars to combat the "pulling during braking" that improperly adjusted drums can cause.

Personally I am not sold on the concept of discs on the rear....especially if you are expecting better stopping. They may look great...if that is all you are looking for. I'm not saying don't do it, it can be done, and done safely...just don't expect a great difference in stopping power. Discs will clean better on a 4x4 but they will act odd (slippery) when the are wet.

I do remember working on many mid/late 80's trucks with the self adjusting rear proportioning valve. The main thing about it at the time is that it had to be adressed when lifting 4x4s.

LET ME GET THIS STRAIGHT.... POWER BOOSTERS WERE ADDED FOR DISC BRAKES?? ARE YOU SAYING THERE WERE NO BOOSTERS EVER PRIOR TO 1971??
Drums don't have the fading with heat problems or the wet performance problems of discs either. Look at dump trucks and semi trucks/trailers.
I GUESS YOU'VE NEVER DRIVEN A DRUM BRAKE VEHICAL THRU A BIG WATER PUDDLE??
The real advantage of disc brakes has to do with the lazy and mechanically inept average driver.
THAT DOESN'T EVEN JUSTIFY A REPLY
with a few qualifications "drums are better than discs".
EVERYONE IS ENTITLED TO THERE OWN OPINION.... AFTER ALL... ALOT OF PEOPLE THOUGHT PENICILLIN WAS BAD JU JU & FROM THE DEVIL .. BUT IT TURNED OUT O-K. JOHN

SORRY BUT I'LL STILL HAVE TO CALL B/S ON YOUR WHOLE ARGUMENT

[hilljob26]

i love the rear disc brakes.i have them on mine,and would never ever go back to drums,you can do it cheap,or u can put a couple of dollars into it,it just depends what your budget will let u do.but i have had nothing but good luck out of mine,this damn thing stops on a dime

[LONGHAIR]

LET ME GET THIS STRAIGHT.... POWER BOOSTERS WERE ADDED FOR DISC BRAKES?? ARE YOU SAYING THERE WERE NO BOOSTERS EVER PRIOR TO 1971??

I didn't say that they didn't exist, I didn't even say that there weren't vehicles made with non-power discs ('cause there were). The point was that power became a necessary part of disk brakes, they are now standard equipment on even the cheapest of cars. I don't belive that you can buy a new vehicle with non-power discs.

Drums don't have the fading with heat problems or the wet performance problems of discs either. Look at dump trucks and semi trucks/trailers.

I have...I used to be a pretty hardcore off-roader with lots of creek/trail driving. I know how quickly discs will slip. a few pumps and you are ok again, but that first hit is nearly worthless.
I didn't say that drums were perfect, I even listed some disadvantages, but the point still prevails most big trucks are drum and may have discs on the front.

The real advantage of disc brakes has to do with the lazy and mechanically inept average driver. THAT DOESN'T EVEN JUSTIFY A REPLY

why not? The average driver puts gas in and drives, they have absolutely no idea what is in/under their car and how to deal with it. Do you honestly think that people would put up with having to crawl under their car every weekend to adjust their brakes? Hell, that's why so many clutches are hydraulicly operated, along with reduced pedal effort.

W/O your power booster your discs would get old pretty quickly. I didn't blanketly state that drums were better, just that there is certainly nothing wrong with them and that there is no stopping advantage to rear discs. Rear discs are purely a bling thing............nothing wrong with that either.

[Shane]

The ORIGINAL reaon the car manufacturers switched to disc brakes is pure economics. There are less parts in a disc brake system versus a drum brake system.

[screamin_c102]

Originally Posted by junkyardjohn

SCEAMIN_C10.....THIS IS THE FIRST TIME I'VE EVER HEARD OF ANYONE EVER SAYING THAT DRUMS WERE BETTER. I'VE HEARD ALOT OF PEOPLE SAYING THAT THERE DRUMS WERE GOOD ENOUGH (ALSO ) BUT NEVER BETTER THAN DISCS. I GUESS EVERYONE IS ENTITLED TO THERE OWN OPINION, BUT UNTILL YOU CAN EXPLAIN HOW ALL OF THESE PROBLEM AFFECT DISCS & NOT DRUMS, I THINK I'LL HAVE TO CALL B/S. PLEASE ENLIGHTEN ME. JOHN

I don't recall saying that drums are better than disks, I suggest you re-read the post, and refrain from putting words in my mouth.

I said in a nutshell that unless you spend a few bucks and know exactly what you are doin then leave well enough alone. Disks are a better setup than drums for most occasions, but only if properly designed into a system. I think it unwise to "rig" a braking system together and take your own and other peoples lives in jeopardy on the interstate. I live in a state full of hillbilly's (present company excluded) and NO inspections. You ought to see the sh!t on the road here, usually 'cause Bubba thought it was a good idear, his 9th grade education outways the PHD that originally designed the system.

I also stated that if you design the system into a vehicle that will not vary alot in rear end weight ie. cars, blazers, trailer queen trucks, and what not thaen you could probably get away with it safely on the cheap (brackets, calipers, proportioning valve, and MC)

This may have been the first time you thought you heard drums are better than disks.

This is not a black and white "Drums good/ Disk bad" statement. There are certain conditions in which both have outstanding attributes.

Drums fade and don't grab as well as disks in panic stops, I would prefer that in the rear of a non ABS truck.


As far as adjusting your driving style, that is a load of crap in my book. There is no time to adjust anything in a panic situation. You either give it the brake, give it the gas, or take the ditch. Your vehicle should be ready for either of the first two. Brakes are not something you screw with, especially if you are a novice.


Just my $.02

By the way, the Caps Lock key is on the left side of the keyboard, consider yourself enlightened.

[screamin_c102]

Originally Posted by DTerry

Hey screamin, what's up... (DTerry's dad again)

Hey how's it goin' Thanks for the comments on this topic, they were both experienced and intelligent, I really appreciate it.

I didn't realize I was gettin' bashed around on this one so much

I figured the guy is young, has a wife (maybe a kid) and lives in California. He's gonna need his brakes eventually.

Thanks again....Bill

[Dean23]

a little tid bit on disc brakes for ya

Though disc brakes rely on the same basic principles to slow a vehicle (friction and heat), their design is far superior to that of drum brakes. Instead of housing the major components within a metal drum, disc brakes use a slim rotor and small caliper to halt wheel movement. Within the caliper are two brake pads, one on each side of the rotor, that clamp together when the brake pedal is pressed. Once again, fluid is used to transfer the movement of the brake pedal into the movement of the brake pads.

But 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. Not surprisingly, it was under racing circumstances that the weaknesses of drum brakes and the strengths of disc brakes were first illustrated. Racers with disc brake systems could carry their speed "deeper" into a corner and apply greater braking force at the last possible second without overheating the components. Eventually, as with so many other automotive advances, this technology filtered down to the cars driven by everyday people on public roads.

[Russell]

Biggest issue with disks is getting crap stuck in them. It happens all the time with my father's 05 work truck (he spends a lot of time on crappy "gravel" roads up north)

That and the whole bias stuff. It can be tough to get the bias just right. I've had no problems with my drums getting me stopped, so I'll just stick with them