My rear disc conversion

[swervin ervin]

Well today, sore fingers and all, I started stripping down all the brake stuff on the truck. I couldn't take not doing anything any longer. I haven't got the plans for the rear disc conversion yet, but I have a good idea of what I'll be doing.

I ordered my disc/disc master cylinder and combination valve. I found out I don't need a new booster. I took off the master cylinder and combination valve, removed the drums and brake shoe stuff. Took off the rear end cover and drained all the grease. Probably Monday I pull the axles and remove the backing plates.

The plans show the caliper mounted at the top, which from all my reading won't work right. The bleeder fitting needs to be at 12:00 in order to be able to bleed all the air out of the system. I plan to rework the mounting brackets so I can mount the caliper like it should be, which is just about horizontal, or like the fronts.

I've seen where a lot of folks have trouble with brake bias and low pedal when converting to rear discs. In order for the rear discs to work right, you must use a disc/disc master cylinder and combination valve. This solves the problem of fluid level for the rears and the disc/disc valve solves brake bias problems. Also a disc/drum master cylinder don't have enough pressure for rear discs. A disc/drum combination valve will cause the rear discs to drag because it has a built in residual valve which is needed to keep pressure on the brake shoes so they will stay close to the drum.

Not sure yet on what calipers I will use. I know the ones for the Sevilles have a built in park brake but I don't care for having to use the park brake everytime I park the truck. This is the way these calipers adjust the brakes. A standard caliper like the fronts are self adjusting, but have no park brake feature. I don't ever use a park brake so I might just go with a front style caliper. I found out if you do use Seville type calipers and don't use the park brake feature, it will quit working. I believe I will need to resize the axle flange so the rotor will slide over it. I'll find out more on this when I get the plans and dimensions.

Can't wait to get started on the brackets. I love to fabricate stuff from scratch. Having plans will make this process easier. I'll keep everyone up to date on how everything goes.

[C-10volvo]

i am interested on how this turns out for you, keep us updated on what you end up putting on. its been awhile since i've seen you around here!!

[apstguy]

I don't think it is a good thing to get rid of the e-brake because you don't use it. Remeber, if you loose all hydraulic pressure, you're screwed. I've had it happen to me and would never drive a car without an e-brake. That is why it is called an EMERGENCY brake. That is just my 4¢!

[swervin ervin]

Tyler,

you are right. I've had a brake hose bust before and had to drive home about 20 miles with nothing but an e brake. I'll probably investigate more into the Seville calipers when I get the plans on everything. I don't guess it would kill me to use the e brake when I park, but it could kill me not to have a e brake at all.

[BaggedC10]

Originally posted by apstguy
That is why it is called an EMERGENCY brake. That is just my 4¢!

Actually, it's called a parking brake. It's purpose is not for emergency situations but it works.

[82 Silverado 4X]

Mike,
Having owned an 85 Seville for over 5 years I can tell you that the rear disc system on them are great when they are all set up and bled correctly. But, they can quickly become a nightmare when they aren't. Unless you are the type of person that uses the E-Brake on a regular basis the rear calipers will give you more problems than it's worth. Just my .02 .

[RockHQ]

Mike, FWIW, you needn't really worry about the bleeder screw positioning. When you need to bleed the brakes just unbolt the calipers, position them correctly and use an old rotor or something of the same thickness in between the pads to keep the piston from coming out. I know it's not very convenient but it works.

[RockHQ]

BTW, which master cyl are you going to use?

I'm going to run rear discs, but i'll be using the hydroboost booster which i believe limits the available master cylinders to, uhh.., one type.

[swervin ervin]

You know what? Seville calipers are expensive. I found them for $280.00 for the pair. This includes calipers complete with the e brake parts, pads and bolts. This is the best I've found so far. Still undecided about using them. I'm just not one to use the park brake all the time and from what I read and hear, if you don't use it on a regular basis, it quickly messes up the calipers.

I've read so much on this, my head hurts. I went with a new master cylinder and combination valve from mpbrakes

I read somewhere that 77 Lincoln Continental rear rotors are 5 on 5 and will work like a charm. Other than this, you will have to redrill others to make them work.

[bigblock73]

Mike, yes, the mid to late 70's Lincolns had rear disc brakes and a 5 on 5 BP...thay also had 9" rears.

I do not know the with of the assembly, but if you could find one and it was close in width...that might be a good upgrade. The nine inch rears are easier to change gears, and are stronger than your 10 bolt (I think you have a 10 right?)

I am thinking about doing it, but my main concern at tis point is to get the truck finished...I can always upgrade as time and money allow.

[Jonboy]

What about 77-up Devilles and Fleetwoods. They had the 5 on 5 pattern, rear disc brakes, and I believe my 78 Fleetwood still had a 12 bolt. You could probably buy a whole car for less than 2 calipers.

[dmec]

i have done this cad conversion. the axle flanges require turning down on a lathe to fit inside the rotors. the rear calipers consist of a piston within a piston. the outer piston is for braking. the inner piston is mounted on a screw and controlled by the e brake cable. that is why you have to set e brake to adjust rear brakes. the lever turns the screw which takes the slack out of the inner piston which then reacts on the outer piston. i planned on using the cad master cylinder and proportioning valve. never got a chanch to test. sold the rear end before i could get it installed. since then i have aquired the rear disc set up from a 92 caprice. the rotors fit over the axle flanges without lathe work. havent started on that installation yet. i think the 92 caprice rotors with 77/79 cad seville calipers and home made bracket would work well. i can get rebuilt cad calipers for $200 with no core.

[rage'nrat638]

wilwood disc's with e-brake

[1FaastC10]

Mark, does that caliper have dual bleeders, or are my eyes playing tricks on me??

[79BIG10]

Mike don't you have to have the E-brake connected for inspections purposes? I know we do here in Texas.

[low 84]

Originally posted by 1FaastC10
Mark, does that caliper have dual bleeders, or are my eyes playing tricks on me??

most likely so they can be mounted in different locations. the bleeder needs to be at the top because thats where the air rises. so with one on each end, the calipers can be mounted on the back side like they are or the front side

[Slonaker]

Originally posted by low 84


most likely so they can be mounted in different locations. the bleeder needs to be at the top because thats where the air rises. so with one on each end, the calipers can be mounted on the back side like they are or the front side

It might also allow you to use the same caliper for the left or right side. That is just a guess...

Slonaker

[Grim Reaper]

Originally posted by swervin ervin
You know what? Seville calipers are expensive. I found them for $280.00 for the pair. This includes calipers complete with the e brake parts, pads and bolts. This is the best I've found so far. Still undecided about using them. I'm just not one to use the park brake all the time and from what I read and hear, if you don't use it on a regular basis, it quickly messes up the calipers.

I've read so much on this, my head hurts. I went with a new master cylinder and combination valve from mpbrakes

I read somewhere that 77 Lincoln Continental rear rotors are 5 on 5 and will work like a charm. Other than this, you will have to redrill others to make them work.

The 76-78 Caddies will fit the thick vented rotor used on the fronts of 4x4's That's why they are so popular. The 81 up is actually a better set up and easier to make the parking brake function BUT it will not fit a front vented front disc unless you maching half or more of the pad off.

Best prices I found was Advance Parts. That is eating the Core charge.

I have a 90's 10 bolt disc assembly. It's a slick set up but would require some of the same work with machining the flange to work. The mounting flance for the backing plte and caliper mount are also turned 45degrees to what a 12 and 80's 10 bolt are.

The parking brake is sweet. It's a drumbrake withing the disc hat. Somebody has a complete 10 bolt with the disc set up and 3.73 gears for sale on CK5 right now. ANother couple years and they will be showing up at the pick a parts for decent prices. Right now they are getting a arm and leg.

Hay check with your local GM dealer. When people blow the granade locker and trash the axlehousing they replace the complete axle including the brakes. That's where the one I have came from. it was in the Dealers dumpster and some dumpster divers got it for scrap for their meth habit. I noticed it on their truck and I talked them out of it when they were diving the dumpster here.

[87Silvy]

There's a '85 running around here that has a four wheel disc conversion.

[Grim Reaper]

Ohh yeah I just reread you post. Stock master has more then enough pressure. It has a bias problem because it's WAY to much brakes for the rear. If I didn't adjust the bias on my truck I'd lock 35's EVERY time I tried to stop...that's stock master on there. 76-78 Caddie had rear anti lock brakes. .

The problem with the bias lies in the disc size and the piston diameter. On a modern car you will notice that the rear dist is smaller then the front and smaller calipers are used most times. The smaller disc and calipers help adjust the bias. I needed to pull about 30% out with a adj PV to get my truck biased.

2lb residual valve in the rear circuit will firm up the peddle.
I modified the Combination valvel into a distribution block with presure fail indicator.

Here is a little write up that will tell you how.