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This BMW rotor originally is made for caliper with one big cylinder. however, this caliper fits fine even it leaves inner surface unused; the pads are working with jus about its whole surface. This disc is 296 mm diameter. There is also 302 mm BMW discs available, which would be even better choise to ensure whole pad surface use.

After I have tested these (succesfully?) I´m going to machine the unused surface away to reduce the weight a little bit.

EDIT: This setup fits inside the original 6x15" Audi 100/C4 steel wheel (ET 45). I´m going to use 7x15" alloy wheels with ET from 35 to 40 and the tires from 195 to 225 x 15". The front springs must be modified also to make more clearance to tires.

Here are some pictures of the rear disc and caliper.

Disc is 285 mm diameter and caliper is with 52 mm piston and hand brake.

func412 wrote: caliper is with 52 mm piston and hand brake.

Wow, that is a big piston for the rear!
So, then you can use nice, even bigger ones for the front

Keep it going!
Thanks for the update,
Walter

I remembered incorrectly the size of the piston... it is even bigger; 54mm.

I assume I must change the master cylinder also. I think 22 mm would be good. Do you guys know any good alternatives to 412 (bolt-on?).

...Some pictures and video from last weekend test session on ice, with original brakes.

first photogallery
second photogallery

Cool!
Nicely lowered

Here's a video of our fun at the german Autobahn with my yellow 412. Mostly shot on the way back, hence the line-up

http://videos.streetfire.net/video/E207 ... AFC390.htm

Greets,
Walter

Sweet videos guys, thanks!

Hmm, couldn't see the video, I can only hear the sound. Has probably something to do with my windows98 (yes, I love all classic things ).

Bulley wrote:Has anyone attempted to fit newer-designed, larger discs to a 412? how about on the rear? I'm thinking specifically about the A2 Jetta/Golf GTI set up, but I'm interested in ideas/experieinces.

------------------
Matthew

After much consideration, my plan is now the following:

Rear--
* 20th Anniversary Golf4/Jetta4 rear calipers: 38mm piston, internal ebrake, 3.5" caliper mount spacing, aluminum body, designed for 22mm rotor. Modifications - spot face outboard face of caliper carrier and bore/slot mounting holes to dia. .437" x 3.701" on center for direct mounting to 944NA ('83-85) backing plate.
* Porsche 944NA rear rotors: 20x290 vented, 71 mm overall height
* Porsche 944NA backing plate. Modifications - no ebrake shoes, enlarge seal bore to 63mm for type 4 seal and clearance "throat" for type 4 bearing.
* Modify type 4 hub for 5x130 studs (probably 66mm)
* Fabricate aluminum hub adapter - centers on drum centering boss of type 4 hub, has boss to center rotor, has boss to center wheel. This piece goes between outer stub axle of type 4 and rotor. Thickness is TBD (about 24mm) and locates rotor centered in caliper.

Front--
* 911 "M" caliper: 48mm piston, steel, 3.0" caliper mount spacing
* 944NA front rotors: 20x282 vented, 35mm overall height
* Type 4 spindle (3" caliper mounting) and bearings (Type 1)
* Hub: 944NA modified for Type 1 bearings or Type 4 rotor modified to be a hub -- remove disk/hat, stud 5x130 (may need caliper spacer for lateral centering)

Wheels--Porsche 16" or 17", TBD

With stock master cylinder this will give less than 1.60:1 brake bias.

The rear has been mocked up and fabrication will start soon. The only unknown issue with the front is hub offset, but it appears to have a solution.

Vented/upgraded disks front/rear with ebrake, stock bearings, studs, and "moderate" machining More details to follow as it comes together...

BTW -- kuhl video

BK

The setup looks fine and by the use of aluminum results that the weight is not increasing, I suppose.

I found a calculator which shows how the modifications affects. Really helpful tool.

http://sports.racer.net/docs/brakes.xls

I just don´t understand what means "distance between master cylinder rods"

Bill K. wrote:After much consideration, my plan is now the following:

Rear--
* 20th Anniversary Golf4/Jetta4 rear calipers: 38mm piston, internal ebrake, 3.5" caliper mount spacing, aluminum body, designed for 22mm rotor. Modifications - spot face outboard face of caliper carrier and bore/slot mounting holes to dia. .437" x 3.701" on center for direct mounting to 944NA ('83-85) backing plate.
* Porsche 944NA rear rotors: 20x290 vented, 71 mm overall height
* Porsche 944NA backing plate. Modifications - no ebrake shoes, enlarge seal bore to 63mm for type 4 seal and clearance "throat" for type 4 bearing.

After getting the 944NA rotors and remeasuring, it turns out that the pads will hang off the edge of the rotor. I don't want to slot the caliper carriers radially (and vertically), so I'm going to try the cast iron caliper brackets from AC Industries (p/n 311615425EB, available at So. Cal. Imports). This approach will require the T4 rotor OD to be turned and modification of the mounting holes on the caliper bracket, but will eliminate machining of the 944NA bearing retainer and 20AE caliper carrier, so it's probably an easier conversion.

Two more videos available from icetrack here: http://www.cc.jyu.fi/~jaantika/kuvia/makistartti2006/

The second one (412toka, whatever that means) is my favorit! Very nice oversteer drift
Cool to see a 412 do that

That´s my favorite too.
BTW "toka" really is an expression which means the second one in Finnish language.

Rear disc fitted to hub.