964 C4 Big Red Set Up Question
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Hi All,
From the previous owner, I have Big Reds up fron and 4 piston black calipers in the rear of my 1990 C4. I have not measured or looked for a part numbers, but I assume they are standard later model 964 rear calipers (standard calipers on a 90' C4 werer 2 piston).
I find that the ABS kicks in too early (no tire or road condition related problems) under firm braking.
Short of replacing the rear calipers/rotors, what can be done to correct this?
What about changing the rear brake bias valve to a different bar? If yes, what would be the correct choice for a primary street machine?
Thanks and Best Regards,
Joe.
From the previous owner, I have Big Reds up fron and 4 piston black calipers in the rear of my 1990 C4. I have not measured or looked for a part numbers, but I assume they are standard later model 964 rear calipers (standard calipers on a 90' C4 werer 2 piston).
I find that the ABS kicks in too early (no tire or road condition related problems) under firm braking.
Short of replacing the rear calipers/rotors, what can be done to correct this?
What about changing the rear brake bias valve to a different bar? If yes, what would be the correct choice for a primary street machine?
Thanks and Best Regards,
Joe.
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I find that the ABS kicks in too early (no tire or road condition related problems) under firm braking.
Other C4 owners have found a premature application of ABS due to a dirty or failing accelerometer or perhaps a brake bleed is in order. I would recommend that all basic issues have been reviewed before making any changes to brakes.
There is a current thread on ABS issues in the 964 forum. I can't seem to get the link or URL to show up if you go look, it's titled: 964 Brake Problem!!! Please Help!
Other C4 owners have found a premature application of ABS due to a dirty or failing accelerometer or perhaps a brake bleed is in order. I would recommend that all basic issues have been reviewed before making any changes to brakes.
There is a current thread on ABS issues in the 964 forum. I can't seem to get the link or URL to show up if you go look, it's titled: 964 Brake Problem!!! Please Help!
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Originally Posted by jmattiko
....but I assume they are standard later model 964 rear calipers (standard calipers on a 90' C4 were 2 pistons)....
All 964's had 4 piston caliper fronts.
Marc
#6
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AFAIK, all C4's had 4 piston calipers and only early C2's had 2 piston calipers rear
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Joe:
If my memory serves (I also own a modified 90 c2), there is a proportioning valve just above the ABS unit and i think it cuts 40% of the flow to the back brakes. I removed mine, as did a few other DE/Race guys. (it's easy as it's just a plug in line that can be removed) and after doing so, the total braking system got much better, including a more aggressive abs setting - due to the rear brakes actually helping to stop the car....
andy
If my memory serves (I also own a modified 90 c2), there is a proportioning valve just above the ABS unit and i think it cuts 40% of the flow to the back brakes. I removed mine, as did a few other DE/Race guys. (it's easy as it's just a plug in line that can be removed) and after doing so, the total braking system got much better, including a more aggressive abs setting - due to the rear brakes actually helping to stop the car....
andy
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Several have found that upgrading to the Turbo 60 bias valve makes quite a difference. If you're a PCA member, there was a two part Pano article this summer on brakes, with the July issue focusing on 964 brakes.