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Rear Disc: using front brake stock parts

C

ColAdo82K5

1/2 ton status
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Hey,
Ok, So i have a slightly leaky wheel cylinder in my 12 bolt. So, I start checking out the prices of the parts to redo all of my drums brakes...WAY TOO MUCH ! Even with my discount at AutoZone. So, here are my plans:
Stock 10bolt calipers $12 piece
stock matching pads $16
Stock IFS rotors $25 piece
10bolt front backing plates $free
Brake hoses 1984 cavilier $13 piece
Stock banjo bolts $1 piece
Stock guide bolts $4/ set
Hardware to mount plates $5
Total: Maybe $120 with tax and a discount


I'll be mocking this up on my rear 10 bolt in my garage before I tear apart my 12 bolt in the truck. So save me some headache if you have any ideas. Thanks
Blake
 
This is more or less what I did on my 14b s/f rear. I don't think you'll have to swap wheel studs. The existing ones should be fine. You'll probably have to machine the backing plates to fit on the axletube and bolt to the brake mounting flange on the axletube. You will probably need a spacer between them as well. I would mock it all up first and then measure the thickness needed for the spacer.

It is preferrable to put the rotors on the outside of the axle flange. This let you change them without pulling the axleshafts. It also lets you to have standard wheel studs pressed into the axle flange. Otherwise, the studs are pressed into the rotor and the "hats" may not be designed for that.

You should match the rotor to the axle flange. I used mid-90's front rotors because they fit perfectly on the 6-lug axle flanges. You might have to machine the axle flange down to fit an 80's front rotor.

Oh yeah, another thing. With the same calipers front and rear (like I have) there is way too much rear brake bias. You will need a prop valve to reduce rear pressure to avoid premature rear lockup.
 
That Az-Kickin setup is great. But I was hoping to use my stock front backing plates, because I have seen them used before and that would save me lots of $$.
Blake
 
Blue,
So the 88+ IFS rotors will work huh ? Did you use the composite or the non-composite ones ?
Blake
 
Wow,
I like the use of stock wheel studs and the lack of spacers with the backing plate. Looks great. Grinding the pads looks easy enough.
Must find a drill press for the rotors...I know I'd get it a bit off.
Blake
 
If you buy a Starret hole saw they're usually pretty round. Since the little lip on the rotors pretty much centers the hole saw you just have to keep the saw from walking. I think in the future I'm going to try using a die grinder to do it. I don't know. I don't have access to a large enough drill press to do it. And the guy I could use the drill press to do it on has a nifty lathe that'd do a much better job.
 
I'm just curious if it would hurt anything if the hole was a little larger than necessary? So that if it was off a little it wouldn't matter so much.

Almost forgot to add, "Awesome write up!" /forums/images/graemlins/waytogo.gif Now I'm all giddy and excited. I have an D44 sitting around I can get some of the parts off of. Looks like just as much work as the other aftermarket conversion kit.
 
After looking more at the stock rotors, I understand why I can use them without major machine work.
For clarification, the part of the pad that hits the rotor is the metal backing that rubs the center hat of the rotor, correct ?
Thanks,
Blake
 
[ QUOTE ]

Oh yeah, another thing. With the same calipers front and rear (like I have) there is way too much rear brake bias. You will need a prop valve to reduce rear pressure to avoid premature rear lockup.

[/ QUOTE ]
Where and what kind of prop valve.
 
I think that he means an adjustable valve like race cars uses. Some trucks work fine without modification, but others don't work at all. I think it all depends on the condition of your factory pieces. Some take the pieces out of the stock valve, while others take it out, while others add the adjustable valve.
Blake
 
I've got a WARN full float conversion kit in my 10-bolt, and decided to go with the rear disc option at the same time. I used '88-up front truck rotors (biscuit style) and had the center register enlarged to fit over the hub carrier. I needed to use reducers to get the lug holes in the rotors down to the right size for the stock lugs.

For calipers I used Cadillac rears, because they had parking brake provisions. All that was needed was to have a new set of rear cables made.

I used Monte Carlo brake hoses (braided stainless) and the WARN brackets, which I had to have pocket milled to get the rotors to align properly.

I used a Wilwood adjustable proportioning valve to get the brake bias right. One important thing to look at is master cylinder volume vs caliper piston volume. If the master isn't big enough you will never get full engagement of the pistons. A lot of disc/drum systems use a master with a smaller rear reservoir, which can be too small for rear calipers because they were designed to work with wheel cylinders (considerably smaller volume of fluid). Using a master from a Camaro, Firebird, or Corvette with rear discs can solve this problem. You just need to do a lot of careful measuring and some geometry. Then you will need to test to get the brake bias set right. Ideally the rear brakes will lock just before the fronts. If you can't achieve this condition something in the system is off.
 
Why are people machining the stud holes in the axles or rotors?

I used an adjustable proportion valve from Summit

I didn't know there were composite rotors, so I guess I'm using standard ones.

I also had an issue with the 80's brake pads hitting the 90's rotor hats. I just took off a little bit of the metal on the brake pad backing. This is the only thing that I have to machine for maintainance. Axle shafts, calipers, hoses, caliper bolts, rotors and pads are all stock items.
 
Blue,
That's interesting that you didn't open up the center of the rotor hat. Maybe.......
1. your 14sf has a smaller center section compared to a 10/12 bolt
...OR...
2. your standard rotors(which are non-composite and have thicker centers) have a larger center hat opening. And that the thicker centers don't matter because the 14sf wheel studs are longer then the 10/12 bolt.

I'll check this out at work tonight...
Blake
 
I just looked at your article and your brakes are very similar to mine. The difference is that I used a 14b s/f axle. I had to machine out the backing plate hole to fit over the bigger axle tube. I also had to use spacers because my axleshafts are longer. The nice thing about this is that my rear track width is close to the front. IMHO, it was luck that you didn't have to use a spacer.

Also, I didn't have to machine the rotor at all. I think I said "1995 4x4" front rotor. Is that different from 88? It looks just the same. It seems unlikely that the 14b shafts have a smaller flange on them. I also don't have much room for "waterpipe spacers" because I am running stock 9/16 wheelstuds in back (3/4-ton).

My hoses are the same as stock front ones. Here's an old pic:
1036left_brake_2-med.jpg
 
Sounds to me like you're running IFS axleshafts which are longer (WMS to WMS) than 10/12 bolt. Not to mention the 14mm lugnuts. Since you'd have IFS rear shafts then the hub center will be small like in the front. I believe it's 3 1/8". SFA 1/2 and 3/4 tons had 3.5" hub centers.

I suspect GM used those rotors for a great many years. I know the extended cab trucks got a thicker rotor. I also know that not all rotors are two piece and that some are 1 solid piece... all cast. No stamped steel center. The cast ones' hats won't fit over the ~7 1/8" flange of a 10 bolt shaft.
 
Here are the parts I bought tonight at Autozone...

Rotors 90 K1500: 5569 25.99
Pads: MKD52S 16.99
Guide pins: H5004 4.99*2
Rattle clips: H5408B 1.99
Hoses 84 Cavailer: 77323 or 77324 12.99 piece
Calipers: c528 c529 11.99+10core *2
Banjo Bolt: 313940 1.99*2

The reason I did the 84 Cav brake hoses is that they use the exact same banjo bolt and are only 9.5 inchs long, so they will stay out of the way.
Hopefully will get the arbor bit setup tomorrow.
Blake
 
Keep us posted.

After reading CyberSniper's write-up, I plan to do the rear discs as soon as I get my 10bolts swapped out. So, I would like to know how it goes. Thanks for the part numbers.
 
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