MGA brake conversion

[enjenjo]

I have been working on a disc brake conversion for a 1959 MGA. It's Chevy powered, with an S10 rear end, and he wanted a 4 3/4" bolt pattern on the front too. With some investigation of the rotors available, I found that there were none that would just bolt on, but the closest I could find was, believe it or not, S10. The outer bearing race on the spindle was listed at .75" but actually measured 20 mm. The inner bearing race was listed as 1.187" but actually measured 30 mm. For the 20 mm bearing I was able to find one that was .061" bigger than the S10 bearing, so it was no big deal to machine .0305" out of the bearing bore to make the outer bearing fit the S10 rotor. The inner bearing was not so easy. All the 30 mm ID bearings were either way to big, or too small. So what I ended up doing was making a sleeve that I could shrink into the bearing bore, then turn the inside to fit the metric bearing. Not an ideal solution but workable.


I had to install a spacer on the spindle to take up some excess length in the spindle bolt, and move the rotor out enough to make room for a caliper bracket. The wheel face of the rotor is about the same as the original MGA hub. The spacer ended up being.400" long.

Since there was so much offset I had to fabricate the bracket from two pieces, and weld them together. I used some 3/8" thick material I had, angle iron actually, that I had on hand. I had some new steel for the job, but messed it up on a false start. :oops: The calipers I ended up using are, Surprise, S10.I have a pattern for GM metric caliper brackets that I traced on the steel with locations for the caliper bolt holes, cutting it out with my band saw and drill press. To find the location for the bracket I put a 1/8" spacer on the edge of the toror, and clamped the caliper and bracket to the rotor, and measured the location. I tacked the bracket together, and made a jig to properly locate everything straight and true for final welding, and then welded the second one to match.

After fitting everything in place, I dressed and sand blasted everything and proceeded to paint the parts. I'll do final assembly when I get home from the Zoo.

[enjenjo]

After looking at the pictures, I am going to add some reinforcements to the bracket. Until just now I didn't see it.

[chimp koose]

Speedway motors sells a weld on bracket for GM metric calipers to a 3" tube rear axle for about $10 each . Thats what I used when I did the disc brake swap on my econoline spindles . That is a bit of crafty engineering you have done there! You must have a lot of manuals to reference or a very friendly counter man .

[enjenjo]

Speedway motors sells a weld on bracket for GM metric calipers to a 3" tube rear axle for about $10 each . Thats what I used when I did the disc brake swap on my econoline spindles . That is a bit of crafty engineering you have done there! You must have a lot of manuals to reference or a very friendly counter man .

I looked into that, but the bracket they sell is only 1/4" thick which I feel is too thin for a street driven car. I looked at Speedway, and also UB machine before I fabricated these. If I did use the speedway bracket, I would install a gusset at 90% to the plane of the bracket to keep it from bending.