well im pretty sure you cant use the 9 bolt disk brakes on either of the 9" or 12 bolt so what did you do about it and what did you change

thanks

 

Hey, I did basically what you describe, except I went from a 10-bolt.

If you've got the '89-'92 aluminum calipers, YES, you can use em on the 9".



If you look real close on the right side you can see part of the aluminum caliper.

Here's what ya need to do. Get a set of 90-92 10-bolt disc backing plates. Overbore the center hole in both to fit the 9" axle bearing through it. Then, (and here is the fun part) drill the Ford drum flange pattern into the backing plates. Here's a tip, if you SWAP the backing plates left to right (put the left on the right and vice versa), it makes this a lot easier because it gives you a lot more metal around the holes you're going to have to drill.

Oh, and make sure the 9" is set up with the correct 5 lug chevy bolt pattern.

That's it! Easy eh?

 

cool, great.

im leaning more towards a 12 bolt

im assuming i'd have to do the same thing with that too right?

so i guess the only problem will be the backing plates then correct?

thanks

 

Yup, the backing plates are the big issue. Get the 10-bolt ones from GM and modify those. The 9-bolt ones will never work.

I dunno if you'll have to overbore the backign plates for a 12-bolt or not. The issue with the 9" was getting the bearing on the axle through the hole.

 

Thanks, my biggest issue was if i had to get new brakes

thanks for the help

 

NP. I actually had the old crappy 82-88 brakes and used the 9" as an excuse to upgrade to the 89-92 ones .

 

Actually the 9 bolt backing plates WILL work. I had a 9 bolt and swapped to a Moser 9". You can counterbore the plate like I did on the bearing side to 3.150" to and .125" deep. Using this method will retain the bearing (and therefore the axle) because the bearing will stick out of the axle tubes about 1/8". Then use a 13/32 drill to redrill the plate to the housing. You might have to shim the caliper to align it on the rotor properly. I've had this setup on my car since 1996 and works flawlessly.

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1989 IROC-Z, ZZ3 shortblock with some bolt-ons.
13.20 @ 108.69, 2.2 60'

 

My mistake! I was thinking of the 82-88 10-bolt backing plates (they're too damn thin). I went out and looked at the 9-bolt ones the other night and realized my error.

OTOH, I still think you'd be better off with the 89-92 10-bolt backing plates. Save the 9-bolt plates for people with 9-bolts (i.e. sell them)... It probably would end up being much different in price and the 10-bolt brackets are a bit beefier...