# Converting rear drums to disks, Mk3



## clyde (Aug 31, 1999)

I must be doing something wrong with the Search function. Either that or the Search function is seriously compromised.

Need info about converting Mk3 rear drums to disks. There must be upwards of a hundred threads on this topic, but the lame Search function tells me the "words are too common," the "words are too short," or some other excuse that it can't find any info. Tried searching the entire thread, tried searching titles only—ZERO for 10.

Goal is to put rear disks on a Mk3 that now has rear drum brakes. Would like to use Mk4 calipers because some folks say the Mk4 caliper is less likely to freeze than Mk3 rear calipers.

Questions are:
1. will the Mk4 caliper bolt directly to the Mk3 disk brake stub axle; and
2. what's a practical way of connecting the brake line to the caliper? The Mk4 uses a banjo fitting; the Mk3 used a compression nut. Are special lines available or will Mk4 brake lines work on the Mk3 car?

URL's to thread(s) containing the info would be WONDERFUL! No need to re-invent the brake…

Thanks!


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## clyde (Aug 31, 1999)

Up


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## petethepug (May 25, 2001)

petethepug said:


> Mk III needs to use your existing caliper carriers and they bolt on. MKIV rear caliper fit on MKIII?
> Mk II (All Corrado) needs to use your existing caliper carriers and they bolt on Mk4 Brakes on Corrado & mk4 calipers on mk2 rear disc
> Mk I .. yes Mk I too .. read on Mk4 to Mk I rear caliper swap completed - Pix inside.


Proper Brake Line or Adapter for Mk4 Rear Caliper Upgrade on Mk3?

The threads are old and the good one's with pics and useful info are hard to find. Most of the pics are dead from the hosts going out of buss.


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## OddJobb (Nov 6, 2004)

Well, first it is *disc* brakes, not disk.

I searched 'drum disc' and found 90% of the threads. Use the link below.

http://forums.vwvortex.com/search.php?searchid=43808446

MKIV calipers are aluminum and do bolt directly to the stub axle.

You can either get short rubber brake lines that have the banjo fittings on them and connect them to the drum lines, or if you're more adventurous and want to do it the right way you can get pre-fabricated brake lines with the flare nuts already on them, bend them, and replace the lines from the proportioning valve on the beam all the way to the caliper.


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## vr6eatinmf (Dec 27, 2010)

mk4 calipers bolt directly to an mk3 disc caliper carrier. the hard lines and prop valve you need from a disc brake car. the hoses you need come from a 1999 passat, only a 1999. it has a banjo at one end and a threaded end that threads directly to the mk3 hard line. oddjob your an arrogant bastard, follow your sig, why the hell suggest something you know nothing about, ****in prick


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## germancarnut51 (Mar 23, 2008)

vr6eatinmf said:


> mk4 calipers bolt directly to an mk3 disc caliper carrier. the hard lines and prop valve you need from a disc brake car. the hoses you need come from a 1999 passat, only a 1999. it has a banjo at one end and a threaded end that threads directly to the mk3 hard line. oddjob your an arrogant bastard, follow your sig, why the hell suggest something you know nothing about, ****in prick



The Passat hoses are designed to attach to the trailing arm hard lines on a rear disc brake equipped car.

The best way to add rear MKIV disc brakes to a MKIII is to use the MKI trailing arm hard line combined with the Passat hose, OR the MKIV VW hybrid line which replaces the MKIII trailing arm hard line, plus the hose.


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## clyde (Aug 31, 1999)

"The best way to add rear MKIV disc brakes to a MKIII is to use the *MKI trailing arm hard line* combined with the Passat hose, OR the MKIV VW hybrid line which replaces the MKIII trailing arm hard line, plus the hose."

Did the 83/84 GTI's have rear disks? If not, which Mk1's had rear disks?


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## germancarnut51 (Mar 23, 2008)

clyde said:


> "The best way to add rear MKIV disc brakes to a MKIII is to use the *MKI trailing arm hard line* combined with the Passat hose, OR the MKIV VW hybrid line which replaces the MKIII trailing arm hard line, plus the hose."
> 
> Did the 83/84 GTI's have rear disks? If not, which Mk1's had rear disks?




That's a Boo-Boo. I meant to write MKIII trailing arm hard line. Of course the MKI GTIs also had rear disc brake, but I think the hard lines and the parking brake cables on the MKIs and a lot of MKIIs are reversed from those on MKIIIs. On MKIIIs the brakes cables are low on the trailing arms and the lines are on the top. On MKIs and MKIIs, the brake cables are on the top and the hardlines are run on the bottom of the trailing arms.

There's been a lot of talk about running the rear calipers upside down when installing MKIV rear calipers on a MKII and the dificulty of bleeding the calipers with the calipers mounted upside down and the bleeders on the bottoms of the calipers. If you have a MKII with the brake cables and hoses reversed, I think it's easier to switch the routing of the cables and the hard lines. The funny thing is, when I installed rear disc brakes in several MKIIs, I never noticed the parking brake cables being on the top and the hard lines being on the bottom. Could be that some cars came right side up, OR I reversed the cables and hoses without thinking about it.

If you have a MKIII and you are converting to rear disc brakes, use the MKIII rear disc brake hard lines. If you have a MKIII and you are converting to MKIV rear disc brakes, use the MKIII rear disc brake hardlines, and the Passat banjo bolt hoses. The Passat hoses are exactly the right length to use with the MKIII rear disc brake hardlines. The only thing I did to use the Passat hoses was to use my Dremel tool to put a notch in the bracket that holds the end of the hardline/Passat hose junction, because the Passat hose (that I used) does not have a flat machined for a wrench to hold the hose for tightening purposes. Instead, the Passat hose has a index lug that keeps it from rotating once it is inserted into the mounting bracket.

I have a pair of original VW MKIV hybrid rubber hose/hardlines from my MKIV rear calipers. They would have screwed onto the lines at the front of the MKIII trailing arms, and the MIV calipers and fit perfectly, but I decided to go with the MKIII rear disc brake hard lines and Passat hoses because I didn't like the small diameter/thin walled, and low quality look of the rubber hoses that were part of the original MKIV hybrid lines. Plus the VW hybrid lines were expensive pieces from the VW Dealer, and I didn't want to get raped every couple of years when the hoses needed replacement and the entire lines would have to be replaced.

If you want a pair of the MKIV hybrid lines, I would be willing to sell you mine for a reasonable price, just to get them out of the garage.


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