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Discussion Starter · #1 ·
I have a 2004 Sti that is my dedicated track car that I have been having brake issues with lately. Its hard to describe the issue but I'll try my best.

When going into a hard braking zone, say after a straight, when I get on the brakes hard it feels as if the pedal goes soft. Its not a boiling fluid or brake fade kind of feeling. It feels as if the abs activates, but instead of pulsing like it normally would, it just stays open. If you've ever driven in the snow when the abs activates and you get that soft pulsing pedal, its a similar feeling to that, just without the pulsing. The pedal almost feels kind of spongy until the car slows down a bit, then the pedal seems to come back and it gets hard again. Its as if the abs finally closes and it pulses back. While all this is happening the car is slowing down, but there is definitely a reduction in brake power until the pedal comes back. Also, none of the wheels are locking up while its happening. My brake setup is below, but I don't believe its a fluid or pad issue, as its done it with multiple pads and different fluids.

For reference, my brake setup is:
Stock brembo calipers with anti knockback springs in the front calipers
Hawk DTC-60 pads
Centric blank rotors
05 hub conversion with abs wing adapters (to make the abs system work)
Castrol SRF fluid, bleed before every event
steel brake lines

My initial thoughts are some sort of abs pump issue. Has anyone had this type of issue on a mainly track car before? Are there any good methods to test the ABS pump? It does seem to get worse as the session goes on, so maybe its a heat related issue with the pump? Maybe its my braking technique and I'm too hard on my initial application. I'm open to any suggestions on things to test or check, and I'm curious to hear if anyone has had any similar issues.

thanks in advance!
 

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no brake cooling? hard to believe you are not boiling your brakefluid. Even if its Castrol SRF

You can try a different ABS Block/pump.
Pads in good shape?
Have you asked your trusted Dealer?/Workshop? maybe they can test your ABS Pump
 

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Yessir what you are experiencing is pad knockback. Next time at track toe brake pedal before you really want to use brakes. If no longer soft pedal you confirmed it's pad knockback. The 2004 STi knuckles are smaller than 2005-07 and the bearings/hubs are different. There is quite a bit of flex in the knuckle. I fixed it on mine with a combination of things one main one, 2007 STi knuckles and hubs and the other a master cylinder brace. Haven't looked back since.
 
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