Jump to content

Rear disc brakes



So closing stages of gettiing M2 back on the road I wanted to adjust rear drums…

Alert! Mission creep.

Those shoe adjustment things were solid. Buggers didn’t wanna move no matter what. Then i thought f ’em, I’ll go disc.

Many have done this & kits are available but after shipping & taxes cost would be too much. Because hobby I put tinkering mode on and went diy.


Called local chop chop if they had VW golf 3 or 4 rear calibers. Not surpisingly they did. Went to pick up a pair (20 €) which had new pads on them. Nice. These i pulled out of Bora cause dude said they’re the same as Golf4 and it was top of other car - was easy ( -12C and dark and i was lazy).


Off comes 250 mm drums, back plates, 22 mm cylinders & last pipe section. Venier in hand taking some numbers up and drawing some pics.


Now I didn’t want to turn rear hubs to suit VW front disc I stared searching internet for disc options…

”a few hours later”

found my discs: Civic VII. Rear disc has good dimensions. O.d 260 mm, 9 mm th and off set looks doable. Centre bore was bigger than hub so i turned spacer rings to get them centered. Also drilled & tapped holes for fixing discs to hubs so  they stay in place while wheel is off. I eventually did turn hubs center part radius to flange face smaller ( like E21 has iirc) but might not had to. Dunno, i was tired that night when i figured this part and turned those spacers lol.

I made template/ mock up adapter of 10 mm thick sheet metal. Orginally I wanted to mount caliper 3 o’clock (as in normally) but pretty soon it turned out not to be possible. Shock & bracket steel would be in a way. The way calibers bleed nipple is orientared so that I thought I could get away with 5 o’clock position - I want to bleed system w/o moving rear calibers in order to bleed them. I did grind a bit steel off of the shock bracket to get caliber as high as i could.


Mock up adapter turned out nicely. 1-2 mm fine tuning for caliber mounts was needed. Went and cut some steel for adapters. Then turned them straight & threaded for calibers. 

Disassembled both calibers. One had broken dust cover so bought repair kit and replaced seal and dust boot. At this time i found out that these were not same as Golf4 calibers. G4 has 38 mm piston and these have 41 mm piston! So I’ll find out if this is good or will I need to hunt 38’s to replace these ( 270 mm  vented fronts, 4x40 mm front calibers & 23.81 mm mc). Carriers are going to be attached from the opposite side to adapter than they are in vw. So turned some 1.5 mm from that side off to get flat surface. Then they got media blasted and painted. All innards cleaned put em back together. Needed to buy tool for pushing and turning the piston in. Orginally carriers have threads to attach them to vw trailing arm. My application didn’t allow this. Drilled them through with 10 mm dril bit. Adapters have threads for fixing them in place. I used same vw bolts as orginally (metric fine thread).


Then the hand brake cables. I think i have E21 cables cause 250 mm drums was on. Maybe 02 cables would work the same. Took long spring out from the shoe lever end bulge at the and was just about right for vw lever. Also caliber at 5 o’clock position gave me perfect line for that cable to meet the lever. Lenght was some issue so i welded tube to vw cable bracket to take BMW cable & adjust lenght correctly.


I wanted some back plates for looks and keeping stuff from getting there to give trouble later. Using disc as a template i cut sheet metal pieces. Cut opening for caliber, bead rolled some grooves to stiffen it up & bend the edge a little. These gets sanwitched between trailing arm and adapter plate. Welded 6 mm bolt to support brake line.


Bought golf 4 rear brake lines. Older (febi) version is one piece pipe & hose thing but newer is two piece: hose and pipe are separate. One piece version required some handeling as pipe part had all wrong bends and it was about 10 cm too long. Rebended to suit, cut and flared the end. No biggie. Other (2 piece) was too easy. Made correct leght pipe and that was that. 

Bleeding the system. Jacked rear end until that bleed nipples were high enough to be the high point. It was high but i think i got it. Suspension was at full droop so there room for more if needs to be.


Wheels... E30 steelies does not fit anymore. They need like 30 mm or so spacers. Bye bye steelies. Liked them. Next my E30 BBS 6.5x14"  basket weaves. No. Need spacers. Not so much. Tried quickly with 5 mm ones. Not quite but close. I think i revisit these later date. Now i had perfect excuse to get me 15" rims i've always wanted.  


Now i need to wait till April/May to confirm brake bias/balace. Fingers crossed :)


Some pics for your viewing pleasure. Maybe in random order.
















Edited by tzei

  • Like 4


Recommended Comments

Today was MOT test and brakes were fine. Fronts measured 2.0 kN and rears were at 1.4-1.5 kN.

Link to comment
Add a comment...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Upcoming Events

  • Create New...