hooger

So I've read a bunch of posts about soft pedal and they don't seem to apply to my situation.

I'm using Motul RBF600
Pagid RS29 pads

There are no visible leaks. The fluid level in the reservoir does not change.

After a fresh fluid flush, the pedal feels fine. I get on track and once the brakes and tires heat up, the pedal starts to degrade. Its not just the amount of travel, but braking performance is also degrading.

Once the degrading occurs, the pedal and braking do not really return to how they felt until a bleed is performed. So on track, i've been bleeding every other session and taking it very easy on the brakes.

I have replaced the master cylinder and have changed brake lines to SS brake lines and the issue still occurs.

My mechanic thinks the only other thing that can cause this issue is a faulty ABS Module/Pump and those suckers are expensive.

I wanted to know if anyone has experienced something like this and if you have any other ideas on what could be causing this.

And if anyone has a hookup on a rebuilt ABS Module/Pump just in case we have to go that route.

Jake951

Does the pedal firm up after the brakes cool down? Have you rebuilt your calipers (new seals and pistons)?

hooger

The calipers have not been rebuilt. If the caliper seals were bad, would there be a visible leak from the calipers or at least loss of fluid in the reservoir.

The pedal never really firms up again until a proper bleed is done.

993GT

all the brake cooling ducts are there and not broken?

hooger

I cooling duct on the control arms are there and not broken. Are there other ducts I should check for?

Spyerx

Assuming you've fully inspected your braking system for issues with the pistons and your cooling is at least stock.

Try a different fluid FIRST and ensure a full bleed with no air in the system. Motul 660. Or better Endless or Brembo HTC64T. Some here like SRF. The latter 2 I mentioned are both used in F1 and pro GT racing. I've used both for 100s of track days with never a soft pedal.

Also, Pagid pads RS29 (yellows) I found to be really hard on HEAT. They seem to put a bunch of heat into the calipers and rotors. My experience was they thrashed rotors. The reason is heat.

So i would first try a different fluid. Then, try a different pad. Endless, Race Technologies, Ferodo all make good endurance pads that work well for track days. Sprint pads tend to be very aggressive on bite and may invoke ABS too easily if you're running street or r-comp tires.

extanker

check the cooling ducts and maybe a different pad material/rotor scuff up and recommended pad bed in

Jferrante

I have a 996GT3 ABS if that is the culprit. Where in NJ are you? Wonder if the RS29's are visually good but actually past their useful life (have heard this before although mine don't do this)

hooger

We're comparing the feel to another gt3 with the same pads and fluid I have. My pads have about 80% life. We can try different fluid and pads, but aren't convinced that's the cause since many people run the setup I'm running and have no issues.

I'm planning on moving away from pagid for my next set and will be getting floating rotors too.

ill definitely try new brake fluid now and see if that does anything since that's quick and easy to do.

hooger

The Pagids are relatively new (80%) life. I'm in jersey city, where are you.

Jferrante

gotcha - Princeton if you need the abs let me know

hooger

Thanks! I'll PM you if we decide to go that route.

powdrhound

What is your bleed procedure? Should be RR, LR, RF, LF. Always bleed outer nipple first, inner nipple second. This is important! Also check for pad knockback by tapping your brakes prior to a hard application. With good fluid and proper cooling I only bleed once a year as a precaution. Good luck getting it sorted.

hooger

Yea, that's the procedure used.

Backmarker

Based on the symptoms it is pretty likely that your issue is fluid exceeding max head tolerance. Do you have cup ducts or regular street ones?

Also this is a stupid/obvious comment but if your rotors are installed on the wrong side the cooling vanes will do nothing. Speaking from experience as I did this and boiled my fluid