PDA

View Full Version : Porsche brake caliper upgrade questions...



Trevor Ely
05-13-2012, 03:38 PM
Hey everyone,

I recently 'upgraded' the front brakes on my '00 B5 A4, but the results have been less than pleasing.

I used the 996 Carrera 2/4 calipers, matched with the B5 S4 rotors and Hawk HPS pads.

Without being too lengthy, basically, the pedal feel is mostly improved and is much more firm, lacking that mushy feel you get from the original cast-iron units. Saying that, they also seemed to have negatively affected the performance, as it's nearly impossible to even make the ABS intervene. Only after a severe leg workout can you manage to muster only a very small amount of ABS intervention.

My thoughts, at this point, are that the original master cylinder doesn't match the Porsche/Brembo caliper's piston size...So, at this point I'm trying to figure out what I should do. Do I need to increase the size of the rear brakes, maybe through some B6 S4 calipers or is there a master cylinder with a smaller capacity that's available for these cars?

Any help is appreciated!!

CamrideA4
05-13-2012, 05:28 PM
Did you upgrade the lines or are you still on the stock rubber lines?

Sent from my DROIDX using Tapatalk 2

Grip99
05-13-2012, 05:51 PM
Interesting. Im about to install my boxster S calipers and SS brake lines on my car. I hope thats the issue instead of the master cylinder.

mtg729
05-13-2012, 09:22 PM
I have boxster calipers on BIRA brackets with s4 321mm rotors. My abs is currently inop but if I hit the brakes quick enough my system has no problem locking the fronts up. Your master should be alright in that area.

Have you tried on a wet surface? Or a higher speed quick stop?

bmarshall
05-14-2012, 03:23 AM
Have you blead the system correctly or you could have a problem with the pads? Did you clean the anti corosion stuff off the disk? There are programs and formulas to calculate the pressure the pad from master cylinder to caliper ratio.

.Mad Hatter.
05-14-2012, 05:31 AM
Maybe a stupid question but, did you properly bed the rotors prior to testing out your ABS?

034Motorsport
05-14-2012, 09:42 AM
Hey everyone,

I recently 'upgraded' the front brakes on my '00 B5 A4, but the results have been less than pleasing.

I used the 996 Carrera 2/4 calipers, matched with the B5 S4 rotors and Hawk HPS pads.

Without being too lengthy, basically, the pedal feel is mostly improved and is much more firm, lacking that mushy feel you get from the original cast-iron units. Saying that, they also seemed to have negatively affected the performance, as it's nearly impossible to even make the ABS intervene. Only after a severe leg workout can you manage to muster only a very small amount of ABS intervention.

My thoughts, at this point, are that the original master cylinder doesn't match the Porsche/Brembo caliper's piston size...So, at this point I'm trying to figure out what I should do. Do I need to increase the size of the rear brakes, maybe through some B6 S4 calipers or is there a master cylinder with a smaller capacity that's available for these cars?

Any help is appreciated!!

This is a very common misconception. The A4 master cylinder is large enough to use an 8 piston caliper, but realize that piston count really has nothing to do with master cylinder size. An 8 piston caliper can hold less fluid and require less displacement then a small 2 piston caliper. People have been installing brakes much larger then your Porsche 4 piston calipers for years and years; you are not the first person to do this.

First and foremost, did you properly bed the rotors and the pads?

Secondly, did you bleed the ABS? While it is rare, it is sometimes necessary to cycle the ABS via VAGCOM while bleeding the calipers as air can get into the ABS unit and cause what you are experiencing.

As far as larger rear brakes, you are right on the cusp of requiring a larger rear rotor to maintain brake balance, but this is NOT the reason you are experiencing your issue. The only difference that would make would be a more even feeling under braking, rather then it feeling like your rear end is squirming under heavy braking.

You most likely did not properly bed the pads/rotors, or you got fluid on your pads/rotors, or you need to bleed your ABS.