Jump to content
Ultimate Subaru Message Board

Rear Disc Conversion for Gen 1's

Recommended Posts

in the interest of keeping everybody informed i'm gonna share how i did my rear disc conversion... this is NOT a bolt on conversion like the ea81 cars like i originally thought... i was unable to take pictures of what i did but i will discribe it the best i can then perhaps take pictures later when i have time...


DISCLAIMER!: if you screw up don't blame me...



parts: (found on RX, GL-10, and turbo cars in general... mine came from an 87 RX)


-caliper bracket/holder

-backing plate

-rotor and hub


-shims for the pads

-all hardware



-14mm, 36mm, 21mm sockets

-10mm, 17mm wrenches


-some sort of torch(a good hot one)

-angle grinder

-vice grips

-needle nose pliers

-if available, impact gun is gonna make this a LOT easier...



-felt marker or something. chalk?

-spray paint


PREP: alright start this early in the morning... i learned that lesson... have all your parts ready and waiting... it sucks when you're half way through a job and you forgot something...




1. jack up the car and loosen the wheel lugs(21mm) and remove the cotter pin from the center nut. loosen the center nut.


2. jack up the car the rest of the way and PUT A JACKSTAND. remove wheel and remove center nut w/ washer and cone washer.


3. remove the drum. (this can be tough. if so, try putting the wheel back on and using it as leverage.)


4. undo the brake line behind the brake using the 10mm wrench. be carefull! if you screw it up and slip its very easy to snap the bleeder nipple off! if it breaks off it is an expencive and annoying to fix it if your disc conversion doesn't go as planned. plug the now leaking brake line with something. or clamp the soft line located up the control arm using the vice grips.


5. there are 3 14mm bolts going through the drum which attaches the drum to the control arm. remove all 3 (easiest with a deep socket) and put them aside. if you got all the hardware from the parts car then you shouldn't need them. the ones that come with the disc brakes are longer to make up the different thickness of the backing plate.


6. so this is where it gets hard... you can (of you want) remove the gravel guard from the backing plate. i don't like them all that much and they get packed with mud and ruin rotors from heat. try just test fitting the backing plate onto the control arm. you should notice a few things.

-the very end of the control arm is going to be blocking the placement of one of the caliper bracket bolts.

-on multiple spots the control arm will hit the backing plate stopping it from setting down properly against the control arm


7.first up is to make that caliper bracket bolt fit. remove the backing plate and attach the bracket first while its off the car. on the bolt that conflicts with the control arm remove the lock washer then grind the end of the bolt down flush with the caliper bracket.(if you don't grind it down it may rub against the rotor and ruin it.)


8. you're still not going to clear from just removing the washer. get out your torch and heat up the end of the control arm until its nice and hot. get out your BFH and hit it nice and hard so you bend the end of the control arm back. (it sounds worst then it really is)


now that bolt SHOULD clear. if not, reheat and bend it more.


9. you'll now notice that the backing plate is sitting much flatter against the control arm. but not good enough. some parts of the lip going around the edge of the backing plate need to be ground down. use a marker or chalk and mark every spot that it touches. grind those down. (don't go nuts here... the less grinding the better.)


10.aright so you'll notice that the backing plate should now sit flat against the control arm like a nice brake should. YIPPY! alright calm down you're not done yet. test fit your caliper and backing plate(which should also have the caliper bracket on it) onto the control arm. you'll notice that the caliper will hit ever so slightly against the control arm. mark it on the control arm with you chalk or marker. now PLEASE be gentle. control arms are important! grind away the spot on the control arm enough for the caliper to clear. take your time with this.


11. spray all the spots you ground down with primer or spraypaint to protect from rust.


12. bolt on the backing plate and caliper bracket. now take your rotor and hub assembly and seperate them. (4, 14mm bolts) then slip the rotor onto the control arm. you'll notice that if you try to just put on the whole assembly it will not clear the caliper bracket. hence the seperating. put the hub on and tighten the bolts to 15ft/lbs.(i think) these don't take that much force!


13. put in the shims into the caliper bracket and install the brake pads. bolt on the caliper when you're satisfied with the fit of your brakes.


14. connect your brake line from the caliper. use the 10mm and 17mm wrenches to tighten it. make sure its tight! (you will most likely have to bend the brake line to fit. be gentle!


15. put in the cone washer, washer and center nut. (doesn't need to be super tight just yet. wait till the car is on the ground for that)


16. bleed the brakes. (if you don't know how find someone who does) and be sure you remove the vice grips(if you used them) from the soft brake line!!!


17. before bolting on your wheel just check over all you've done. make sure you haven't missed anything. then bolt on the wheel. lower down the car and repeat for the other side. there! disc brakes!


have fun everybody!

Share this post

Link to post
Share on other sites