Who's running B6/B7 S4 front and/or rear brakes? If you are...
12-29-2007, 10:38 PM
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Who's running B6/B7 S4 front and/or rear brakes? If you are...
do you feel the need to get the S4 brake master cylinder?
I searched the forum and found that some people think that it's necessary since there's a difference in brake fluid volume between the S4 and stock setups, but some oppose that idea. I'm about to install B6 S4 brakes on my car and was wondering whether an S4 brake master cylinder is worth it.
Thanks in advance!
I searched the forum and found that some people think that it's necessary since there's a difference in brake fluid volume between the S4 and stock setups, but some oppose that idea. I'm about to install B6 S4 brakes on my car and was wondering whether an S4 brake master cylinder is worth it.
Thanks in advance!
12-30-2007, 03:38 AM
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Wrong and as you may have guessed I tried the the S4 master cylinder...
The S4 master cylinder is bigger than the A4 unit. It does fit physically in the A4's position.
Technically to keep the brake system "properly balanced" if you upgrade to both S4 front and rear brake sizes you should use the S4's bigger master cylinder however the difference may not be that noticeable.
One reason STaSIS won't sell you their 6 piston caliper kit is the A4's master cylinder size. So keep this in mind with any BBK upgrade.
Back to the S4 master cylinder install... Unfortunately it <b>does not work!</b> Without going into all the details, we came up with the conclusion that because the S4's MC moves more fluids and the fact that it is a "two stage" unit, perhaps it screws up the ECU/ABS system and will not release the brake pressure once you start applying the brakes. Also the amount of brake pedal effort required to push on the brake pedal was unbelievable as if the booster section was none functional, again we think because of the design of the unit.
Once you had pushed very hard a few times on the brake pedal, the brakes would not release and the only way we manged to get the brakes to release was to crack open one of the brake lines on the ABS unit.
In short don't bother trying it because I've done yet again the experimenting for you.
Technically to keep the brake system "properly balanced" if you upgrade to both S4 front and rear brake sizes you should use the S4's bigger master cylinder however the difference may not be that noticeable.
One reason STaSIS won't sell you their 6 piston caliper kit is the A4's master cylinder size. So keep this in mind with any BBK upgrade.
Back to the S4 master cylinder install... Unfortunately it <b>does not work!</b> Without going into all the details, we came up with the conclusion that because the S4's MC moves more fluids and the fact that it is a "two stage" unit, perhaps it screws up the ECU/ABS system and will not release the brake pressure once you start applying the brakes. Also the amount of brake pedal effort required to push on the brake pedal was unbelievable as if the booster section was none functional, again we think because of the design of the unit.
Once you had pushed very hard a few times on the brake pedal, the brakes would not release and the only way we manged to get the brakes to release was to crack open one of the brake lines on the ABS unit.
In short don't bother trying it because I've done yet again the experimenting for you.
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12-30-2007, 11:40 AM
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Well I'm not sure if anyone went BBK upfront and put S4 rears on. Pehaps ask here or on a AZ or AG..
However if Audi felt it was better with a bigger MC then perhaps there is a reason behing it.
If you have BBK up front you could just upgrade to the 3.0 V6 rears and that's plenty enough because I have not gone through a set of rears (3.0L) even with all my tracking.
If you have BBK up front you could just upgrade to the 3.0 V6 rears and that's plenty enough because I have not gone through a set of rears (3.0L) even with all my tracking.
12-30-2007, 11:55 AM
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Then I guess he would be the one to ask. I, when I could not use the S4 MC...
Decided to stay with my present rears until I can do it right and I'm working on that solution now but it will not be for everyone because it is going to be a track/racing car solution.