Rear Disk Brake Fitment 72' Cutlass

[#1CutlassSupreme]

Hey everyone,

I see a lot of posts about disk brake conversions on the rear, but this problem hasn't seemed to be addressed yet.

I bought a kit from MBM brakes that inlcuded the fronts and rear disk brake kit for my 72'. The car originally had stock front disks, but the kit was reasonable so I just bought front and backs all together.

Anyway, I ran into an issue with the rear rotor being about 1/32" too small for the hub. To fix the problem I used a drum sander bit on my drill and routed out the inside of the rotor, then I also used my grinder with a sand flap disk to grind a little off of the axel hub. No problem there.

BUT now I have SSIII JJ 15x7 wheels and the calipers are rubbing on the inside of the wheel even thought the company said that they will work with 15" wheels.

I'm thinking that I can just run longer wheel studs and use a 1/2" spacer to set the rim out past the caliper.

I'm just a bit concerned now that I might get some wheel rub on the outter edge of the wheel well. Has anyone else done a rear disc conversion with MBM or are there any pointers you can give me? The rear axle isn't a C-clip axel, it's a 10-bolt that's held in with the bearings and dust covers.

Any short cuts or tricks are greatly appreciated.

Also, any ideas on how to run the brake lines from the back distribution block to the calipers? They gave me some flex lines, but they're too short.

[joe_padavano]

Originally Posted by #1CutlassSupreme

BUT now I have SSIII JJ 15x7 wheels and the calipers are rubbing on the inside of the wheel even thought the company said that they will work with 15" wheels.

As you have unfortunately found out, there's more to specifying the shape of a wheel than just the diameter and backspacing. The contour of the backside of the wheel is very important. Unfortunately, the SSII/SSIII wheels are atypical in this respect. To save stamping costs, Olds developed only one stamped center design for the SSII/SSIII wheels. This same stamping was used on both the 14" and 15" wheels. Since the stamped center is the same on both, the 15" wheels use a special rim that has a greater dropped center than normal. This allows the use of the center from the 14" SSII/III wheels, but also results in the reduced backside clearance. The reality is that the 15" Olds wheels have no more backside clearance than the 14" wheels. Now, having said that, the SSII/III wheels (14" or 15") clear the stock disk brakes just fine.

Also, any ideas on how to run the brake lines from the back distribution block to the calipers? They gave me some flex lines, but they're too short.

Um, how about hard line to the ends of the axle tubes then a coupler to the flex lines?

[#1CutlassSupreme]

Thanks Joe,

I figured that the wheels were the problem. They've got that lip on the inside. The fronts fit fine, but the darn backs are giving me a headache...I should have listened to my dad and stuck with the stock set up, but no use crying over spilled milk.

I'm going to give the 7/16" wheel spacers and the longer studs a try and see if I can hopefully get the calipers away from the wheel far enough and at the same time keep the tires within the wheel wells without rubbing.

I'll post how this goes hopefully by the end of the week. So far this experiment of mine is gonna run me $25 for the new wheel studs and $20 for the 7/16" spacers.

As for the brakes I'm probably going to run some new lines like you mentioned with the coupler. I just hope I can make it look clean.

FYI; for anyone looking for longer wheel studs try part number 610-157 through Dorman. They're 7/16-20 x 2 1/8" with a .475 knurl.

[gearheads78]

Originally Posted by #1CutlassSupreme

Thanks Joe,


As for the brakes I'm probably going to run some new lines like you mentioned with the coupler. I just hope I can make it look clean.

I can't point you right to it because I can't see pics from work but if you will scan through my build tread you can see how I did my rear lines.

[#1CutlassSupreme]

Originally Posted by gearheads78

I can't point you right to it because I can't see pics from work but if you will scan through my build tread you can see how I did my rear lines.

Awesome Thanks Rich!