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Old 09-07-2019, 07:12 AM   #1 (permalink)
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Default No brakes without warning

Hi, I was at Summit point WV yesterday for my first track day. The car did very well, it was setup as 4 20 minutes session with instructor all thr time (group 1). The car does about 415hp, and has ks sport suspension (control pros) stoptech all around with Blue hawks pads.
Most of you recommended the carbontech but the pads from FRsport never came.
So I knew It will be a challenge.
Session one went well, brakes were 200miles old, great stopping power and all,
Second session, 15 first minutes perfect, then down a straight for heavy braking, pedal went to the floor, 3 times, then only one quarter of the travel got a little hard. So I pit in, all went back when brakes rested. ABS light is on from now on.
So I flush about 5 or 6 pedal pump at each wheels a d the brakes fluid was cooked. Next session went ok because I was conscious that they could fell again. After this I bleeded again about 5 pump per caliper.
Last session when hard on them and again they give up with no soft pedal notice, went down to the floor. No I have ABS and Brakes light on.

Tell me if I'm wrong I believe I have two problems here, the fluid/pads carrying to much heat and now the ABS.
Thank you for your inputs.
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Old 09-08-2019, 11:50 AM   #2 (permalink)
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Default Re: No brakes without warning

I'm not familiar enough about the ABS system to comment on that (it's usually the first thing I rip out).

It sounds like the failure mode was lack of pedal pressure as opposed to good pedal pressure but lack of brake force. Lack of pedal pressure means something is happening to compromise the hydraulic force between the pedal and the brake pistons. One idea is that your fluid was boiling. Did you notice empty reservoirs after each session that you lost your braking? Another (probably less likely) idea is that your rubber brake lines were heated by the brake fluid enough to expand like balloons.

I am a HUGE fan of SS brake lines, and good brake fluid like Motul RBF600.

Maybe it was something else ... but if everything was fine after you filled / flushed the brake fluid, it sounds like your cylinders / pads / rotors are OK...
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Old 09-08-2019, 12:21 PM   #3 (permalink)
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Thank you so, I do have ss brake lines, the fluid was always same level, but what I will bleed out of each line was super dark.
To run the motul 600 do I need special seals?
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Old 09-08-2019, 12:24 PM   #4 (permalink)
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Another piece of info, the brake failure happened at the same turn both times and this turn comes after a series of turn without braking at all( about 30-40sec)
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Old 09-08-2019, 12:26 PM   #5 (permalink)
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I have a video on YouTube not sure if that tells anything by my driving, the final lap of the video is with the brake issue because it happened just pass the pit exit.
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Old 09-08-2019, 01:18 PM   #6 (permalink)
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Default Re: No brakes without warning

Hmm, the consistency is interesting. I am not sure what it means, though. I would definitely start with upgrading your brake fluid - no special seals needed for RBF600, and that's only one out of many options. I am currently also running ATE super blue in other cars of mine, that's a good option as well.

I'll note that while I do suspect the fluid as your issue, of course it could be something else entirely - I'm just not sure what else it could be. Admittedly this is ALL conjecture, but to wade in a little deeper, maybe your master cylinder is leaking somehow when it heats up? Or maybe the fluid is sloshing to one side? Wild ideas.
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Old 09-11-2019, 09:39 PM   #7 (permalink)
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Default Re: No brakes without warning

So what brake fluid were you using? How recently before your track day was it bleed? I used to bleed mine before every track day, even if only a month apart. Probably excessively cautious, but cheap IMHO compared to the panic of loosing your brakes at triple digits.

How is your braking technique? How close to threshold braking were you? Braking as hard as possible (without locking up) for the shortest time possible is the best technique for heat management of the brakes. It may seem counter-intuitive, but it's true. Braking less hard for longer puts more heat into the rotors, pads, calipers and most importantly, the brake fluid.
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Old 09-12-2019, 06:11 AM   #8 (permalink)
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The fluid i use was DOT 4 from autozone, it was 400 miles old with very little intensive braking (one day at drag strip and one autocross) the braking technique, I agree with what you are saying , I was staying too long on the pedal to reduce speed. This track has two hard braking (110+ to 50 and 80 to 40 I'm gueesing)
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Old 09-12-2019, 06:13 AM   #9 (permalink)
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Does anyone runs some air scoops on their calipers? My original wheel well plastic is nonexistent (ever had it on driver side) this probably does help channeling cool air.
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Old 09-12-2019, 10:16 AM   #10 (permalink)
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Default Re: No brakes without warning

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Does anyone runs some air scoops on their calipers? My original wheel well plastic is nonexistent (ever had it on driver side) this probably does help channeling cool air.
Ducting to the center of the rotors (air flow is from center to outside diameter) is common for racing setups. Google "brake ducting for racing". It requires a special part to fit very closely to the rotor and knuckle - see the pics when you search. Someone on here made those parts for their own car but I don't think anybody has ever sold them. 3S Warehouse has some simple curved metal pieces that attach to the lower control arm to deflect air towards the brakes. I don't know how effective they are but they're simple to install and can't hurt, only help.

If you weren't using a premium (high temp boiling point) brake fluid, you probably got boiling.

Stock dia rotors with the right pads and fluid will hold up for road racing with the right braking technique for stock power and modest increases over stock. With your hp you'd probably be happier biting the bullet and getting a front BBK (big brake kit). The conversion to EVO X calipers is more affordable than most options. If you keep stock rotors, as your skill increases with more seat time you're going to go thru pads quicker. I used to wear 2/3 to 3/4 of the way thru Porterfield R4 pads in one day of four 20 min sessions and I was on stock turbos and stock boost.
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