Brake Tips for the Track
Anyone participating in Driver's Ed or Autocross would be wise to read this Tip thoroughly!
I had a 928 experience that I don't want to repeat during the weekend. Brake fade. Total brake fade, after only four laps of Pukekohe track. I was fortunately only driving at nine tenths as I had a passenger, but at 110mph at the end of the back straight there wasn't a lot I could do. I tried to spin the car and we went off the track, spun on the grass and came to a halt in deep mud/clay/dirt about 10 feet from the armco. It stopped us well!!!
Unfortunately it was buried up past the axles and took over an hour to drag out, damaging the underside of the car and scooping up so much mud that the wheels wouldn't turn as we winched it onto the tow truck.
I've never had this before running standard pads. I put new disks on the car a couple of days before the event, and a full set of new pads.
Question: What pads are best for road/race use? What do you use Marc Kibort? Devek? Anyone know what Kim Crumb runs? Mark Anderson? David Roberts, do you have any experience and recommendations?
The car is still primarily a road car, but it will get enthusiastic circuit use five or six times a year, so I need to get this right. I still can't quite understand why it happened this time and hasn't before, and I'm investigating the pads that WERE in the car as perhaps they were something a little better than standard.
'87 S4 5 spd, Blue and brown and about 500 lbs heavier
You said you installed new pads. Did you allow them to get broken in ? Also, how old is your fluid ?
I use Cool Carbon Pads and ATE 200 or Super Blue Racing Fluid. I go to Summit Point about once a month where heavy braking occurs for turns 1 & 5. The speeds I'm talking about are 130+ MPH to 65 MPH and 100+ to 30+. I used to get brake fade but not since I don't invoke the ABS.
To the best of my knowledge, Kim Crumb uses Hawk Pads.
How many miles did you put on your new pads before you went to the track?
I turned my rotors and put on new pads and was amazed at how bad my brakes were for a couple days until they set in. I had to take them up on the highway and ride them at speed to deglaze them. Maybe you hadn't burned the glaze off the new pads yet. Are you using high temperature brake fluid? ATE Super Blue or something equal.
Just some thoughts, hope you find the culprit.
Jay F. Kempf
79 US 5 speed silbermetallische
Hawk Performance PLUS Pads for aggressive street driving and moderate track use.
Hawk BLUE Racing pads for very aggressive street driving and Moderate/Heavy track use.
No matter what type of pads you use be sure to follow the "break-in" directions included with the pads. This will keep them from getting "glazed" and will optimize the performance and like of the pads.
I've gone through a lot of brake stuff lately trying to get rid of brake fade at Lime Rock.
First: get rid of the stock pads - almost lost my car that way too (the pads were well broken in). I'm using Performance Friction Carbon Metallic (PFC) 90's - more below on that.
Second: what wheels are you using? Stock S4 wheels don't let enough air through. Simply changing wheels to an open design helped enormously. Fade (used generically here) is nearly (not quite) gone now (and Lime Rock is not a tough braking track). I went to Kinesis Super Cups 8.5&10/17 w/ 255&275/40-17 Kumho's.
I used some temp sensitive paint on my rotors at Lime Rock on Oct 3 (65 degrees). Rotor temps were around 1100F! The PFC 90's stop working about there so I'm still close. At LRP, the braking is chiefly done at the end of the front straight, 125 to 58 mph, through big bend (180 degrees), some braking into the left hander of the esses (no fade), then through the right hander, down no-name straight, and then braking from 95 to 80 for the uphill (FADE!). Actually, it's not fade, but boiling fluid (ATE Super blue) as the pedal is soft.
Now, by the time you get to the uphill, 25 seconds have gone by since you've braked for big bend! I'm speculating that the discs are slowly transferring the heat to the calipers, even as I go down the straight. Since the front has quite good cooling, I'm guessing that it might be the rear brakes even though the fronts do "all" of the braking. Some temp sensitive paint on the calipers should tell this (I did that although I was sent the wrong paint for calipers - you need something that changes about 500F, not 500C). When I take my wheels off after an event, very little brake dust on the inside of the front wheels (a lot on the outside though!). The inside of the rears however, are absolutely coated - this tells me there's very little airflow through the rears and I therefore have to consider I might be boiling fluid in the rear calipers.
Anyway, solve things one at a time. Changing pads is step one. If you still have problems, then new wheels. Then maybe more ducting to one end - dunno which end yet.
Let us know how things work out,
'87 S4 5sp (braking hard enough to occasionally get a little ABS action)
I also have experienced a bit of fade (soft pedal) during my sessions at Summit Point. The hard braking there occurs at the end of the main straight (130+MPH to 60+MPH) and for turn five (100+MPH to 30+MPH).
Like you, I use open wheels (993 OEM Cup) although I don't have quite the width you do. Mine are 8"X 17" & 9"X 17" with 235/45 and 255/40 R1s, respectively. Also, I use the 55 Bar rear brake regulator per Kim Crumb's recommendation. So far the brake set up seems better balanced than with either the stock 18 Bar regulator or the intermediate 33 bar regulator.
I am now getting more use out of my front pads than before, but it's at the expense of the rear pads. Since the front rotors seem to be getting enough cooling, it appears that the rears are now the weak link in the system. Like you, I think improved air flow to the rear pads would be beneficial. Does anyone make a "cool brake" for 928 rear rotors ? If not, here is an opportunity for a niche market product. Actually, it would probably help many other Porsches and non-Porsches. Food for thought.
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