# mk1 rear disc swap questions



## Fritzy1 (Jul 25, 2007)

so i recently decided to do the rear disc swap on my mk1 gti (1983). i got a donor swap from a friend, i beleive it was off of a mk2 jetta, but not positive. the calipers were bad but i replaced them with girling 34's. the propotioning valve he gave me is adjustable but designed to go on the rear beam i beleive. my stock one is under the hood down by the steering rack. is mine adjustable? the one he gave me doesnt look as if i could get it to work. 

i was doing some research and found this on autotechs website 
http://autotech.com/instructions/i698400K,402K, 403K.pdf 

so i know im supposed to adjust/replace the valve, but i dont know where to get one that will work or to set up one of the two that i have. 

advice please?


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## blind (Nov 26, 1999)

I'm not running one on my cabby but the entire brake system has been replaced. I have wilwoods in the front, mk4 calipers in the back, and an audi 23 or 25mm master cylinder. I know it's probably no help but I guess with the right setup you can run without it.


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## deepgrooves74 (Aug 3, 2006)

*more info to add to the post*

(Once you have read what I have written... click on the link at the bottom of my post) 

I hope I can help... learning about this exact subject right now. I have been reading threads all over the web trying to figure this out for myself. This is what I have gleamed so far... 

I believe the adjustable Prop valve they gave you can work, but you have to make a custom bracket to fit it to the rear beam. I believe they came on A2 cars with rear discs. I am currently learning about all of this. From what I have gathered you have a few routes you can take. 

1- First you can run the original blocky looking prop valve that's bolted to your engine bay wall, but I believe you will not get enough pressure to the discs???? Can't remember why that one is bad, but you don't want it... 

2- you can run no prop valve, but I think you will get crazy lock-up... 

3- you could put a manual prop valve in like this one from Summit Racing: 
http://www.summitracing.com/parts/SUM-G3905/ This is a random quick search... not at all a promotion of that specific PV. 

4- There are two prop valves that came on these cars that screwed into the MC directly. One allowed 3.5 bars of pressure to the rear per side (you need two), and apparently from what I have read they came on 8v cars?? The other specifically came on 16v Sciroccos with rear discs (possibly others as well...) and they allowed only 1.5 bars of pressure to the rears. The Scirocco 16v 1.5 bar PVs are the preferred valves to get... I can't remember what the VW# is for the dealership, but I checked there, and you can't order them. I got them used. 

Either way you have to bi-pass the old blocky one... 

This is not the Bible... it is what I have been able to scrap together searching and reading. I have both VW prop valves, and plan on experimenting with both... I will have mk4 calipers in the back, and some sort of 256mm set-up in the front resembling the Scirocco 16v brakes... 

http://forums.vwvortex.com/showthread.php?1776383 

hth


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## deepgrooves74 (Aug 3, 2006)

*wilwoods*



blind said:


> I'm not running one on my cabby but the entire brake system has been replaced. I have wilwoods in the front, mk4 calipers in the back, and an audi 23 or 25mm master cylinder. I know it's probably no help but I guess with the right setup you can run without it.


 I have been looking at Wilwoods as well the powerlite caliper set-up 
http://www.momentummotorparts.com/store/brakingmk1.asp 

Which one are you thinking of using? Probably the bigger ones since you were referring to the 23 or 25mm MC... 

cj


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## Fritzy1 (Jul 25, 2007)

you guys are very helpful thank you. i have girling 54,s up front with ebc pressed rotors, in the back its mk2 parts with girling 34 calipers. im running the stock master cylinder, but i also have the 22mm as an extra. which im not sure if its worth swapping out. 

keep it coming.


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## deepgrooves74 (Aug 3, 2006)

Fritzy1 said:


> you guys are very helpful thank you. i have girling 54,s up front with ebc pressed rotors, in the back its mk2 parts with girling 34 calipers. im running the stock master cylinder, but i also have the 22mm as an extra. which im not sure if its worth swapping out.
> 
> keep it coming.


 Did you look at those threads that were connected to my post? If you run larger brakes you HAVE to run at least a 22mm MC. Otherwise you won't get enough throw from the MC to compress the pads.


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## blind (Nov 26, 1999)

I'm running an older 11" MMP setup. It uses dynalite calipers but I believe their current kit with the dynapros is the same thing. I'm stopping by the garage tonight, so I'll try to see a part number on the master cylinder. 

I'm running the prop valves on the master cylinder but I cannot remember if they are original or from something else. I'll see if there's a number on them too. Talking about this setup is making me want to throw it back together. It's been in pieces for almost three years.


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## blind (Nov 26, 1999)

Here's the number: 441611021A 
I looked it up and it's the 25mm master cylinder. I didn't see a number on the prop valves but comparing their condition to the master cylinder, I think they're the originals. The car is a 91 cabby.


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## Fritzy1 (Jul 25, 2007)

i was looking around for some universal adjustable prop valves and this is one that i came across, will this work for my situation.

http://www.wilwood.com/PDF/DataSheets/ds488.pdf

from this site

http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx


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## Fritzy1 (Jul 25, 2007)

^^^
it looks similar to the one listed in the reply above by deepgrooves. but that one is for a jeep i believe.


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## Fritzy1 (Jul 25, 2007)

http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx 

will this work?


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