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Old 09-15-2012, 04:38 PM   #1 (permalink)
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Brake fade on the track

I need some help problem solving. I started taking my 2001 z06 on the track this year (3 weekends on the track this year). After my first weekend I put on new race pads, rotors, and stainless brake lines. I also upgraded my brake fluid to dot4. After the brake change, my pedal was very firm and stayed firm for most of the next hpde weekend. It was very hot that second hpde weekend, with temps in the upper 90s. The last session I noticed the pedal was soft.

I bled the brakes before my next track weekend and the pedal seemed firm. I did not notice any air bubbles when I bled the brakes. On my next track weekend, my brake pedal went soft very quickly. There was one instance when the pedal almost hit the floor. I was able to pump and get enough brakes to stay out of the wall, but it was a scary corner. I pulled off the track and checked everywhere for leaking brake fluid. I put cardboard under the car in the pits to see if there was any leaking fluid, but after 2 hours not a drop. I decided to take it very easy on the brakes the next session. The brakes felt good at the start of session 3 but faded after a couple of laps., not to the floor but soft enough that the pedal was low. I gave up on the weekend and went home assuming there was air in the line.

When I bled the brakes, no air bubbles at all! Does anybody have suggestions on what may cause this and how to verify the problem.

Thank you in advance for your help. I always say Corvette (and all car guys) are great because we all try to help each other!
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Old 09-15-2012, 08:03 PM   #2 (permalink)
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Re: Brake fade on the track

Low pedal is usually caused by boiled fluid, baked pads, or piston kick back from independent rotor/caliper movement (which gets worse as the pads decrease in thickness).

Specifying your "race pad" selection and track would help. Were you still using the pads from the first weekend at the second event?
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Old 09-15-2012, 08:48 PM   #3 (permalink)
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Re: Brake fade on the track

The pads are hawk HP plus. I put them on after my first track weekend. At the same time I installed the pads I also upgraded the fluid to ATE super blue. I checked the pads when I bled the brakes. There is a lot of pad thickness. The first two weekends were hpde at the Autobahn in Illinios. The third hpde was at Road America.

Is there anyway to tell if the fluid boiled? How would I tell if the pads are baked?

Thanks
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Old 09-16-2012, 06:50 PM   #4 (permalink)
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Re: Brake fade on the track

If it's the pads, the pedal feels firm even when you have no braking. The pedal goes to the floor if it's the fluid. This is my basic working hypothesis. I've experienced the former, not the later.

HP plus are track pads, right?

Assuming everything is new and / or working... It's the weak link almost every time. If the HP plus are track pads, then it's the fluid not fully bled.

This is just my assumption to help you trouble shoot.
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Old 09-16-2012, 07:18 PM   #5 (permalink)
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Re: Brake fade on the track

Boiled fluid gives you soft pedal.

When baked, the pedal feels softer. The bite is gone, so you naturally press harder and the pedal will travel a bit more.

Pad kickback is usually fixed with a single pump on the pedal before entering the braking zone.

The HP Plus aren't really track pads. but getting through 3 HPDEs on them indicates the brakes aren't being used very hard, especially with Road America in the list.

It wouldn't hurt to start it up and press on the brake pedal really hard to make sure you don't have a master cylinder issue. The pedal shouldn't fall under pressure.
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Old 09-17-2012, 11:42 AM   #6 (permalink)
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Re: Brake fade on the track

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Originally Posted by XFordGuy View Post
The HP Plus aren't really track pads. but getting through 3 HPDEs on them indicates the brakes aren't being used very hard, especially with Road America in the list.
Klucius - As a novice myself (from Wausau btw), when it comes to HPDEs I will agree to the above point. The next time you do an HPDE, ask your instructor to give you a ride in their car. After 3-4 events in my Z06, I thought I was starting to "drive the car hard". Then my instructor took me for a ride in his Z06... and I realized I'm not even in the same area code as "driving the car hard".

However, I will say that I can see/feel the progress from one track day to another. My first few days my instructors were giving me very detailed information about hitting brake points, turn-in, apex, turn-out, etc. I was listening and trying to take it in, but it all seemed like a blur when I was on the track.
Instructor: Your braking zone should start at the third crack on the left side of the road, where you see the grass growing up through the track.
Me: Huh? What grass? What crack? I don't see them.
Instructor: Don't worry you'll see it next lap. Ok at this turn, as soon as you feel the car hit the dip wait for the car to settle again then turn in, but not before.
Me: What? I don't see a dip in the road....
Instructor: That's ok, your doing well. You'll get it next lap... Now as you exit this turn, let the car unwind and take you right across the black patch of pavement.
Me: Where? It's all black.
Instructor: Don't worry it's a small patch - you'll see it next lap, but your apex was good there...

Continue this for another 8-10 times per lap and you get an idea of what the coaching is like around Road America when you have a great instructor in the car. But after more track days at RA, more of the necessary details became second nature. My mind was free to think about things other than not hitting a wall or taking an off road ride. I started to see that grass. I started to feel that little dip in the road. I found that black patch.

For me, nothing puts a smile on my face like being able to put that advice into application and knowing that I've made progess because I can actually use that advice and do the things they have coached me to do. When you really start to feel comfortable, you can use your tach as a report card at key corners (assuming your in the same gear every time at a given corner). In the morning you're taking the corner at 3700 RPM, and maybe by mid-afternoon your braking 4000 RPM in the same corner and ready to grab that next gear a little sooner. You don't even have to look at the speedo - more RPM is more speed.

The first time I noticed it at RA was between turn 6 and 7. I was starting to redline before 7 (3rd gear) and the instructor told me "You're hitting your marks better and carrying more speed through turn six, so now 3rd gear is holding you back at turn seven. So rather than maintaining speed and shifting after the corner, short shift and take 4th gear through the corner and build speed all the way down to the braking zone for 8."

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Old 09-17-2012, 03:45 PM   #7 (permalink)
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Re: Brake fade on the track

Hawk HP plus are not a real track pad. 3 track days from them?? They are a great street pad for hard drivers. You need to go one step further and get Hawk track pads and dedicated rotors. Take both off and put your street pads and rotors back on after your track day. I keep them in order and tape up each rotor and pad and mark w/ a sharpie pen. Then you know right where to put them back on for a track day. Track pads make a huge difference but you will need to keep an eye on your piston seals as they can cook off. They can be replaced without buying new calipers.
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Old 09-17-2012, 03:55 PM   #8 (permalink)
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Re: Brake fade on the track

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Originally Posted by seamus2154 View Post
Hawk HP plus are not a real track pad. 3 track days from them??
When Klucius said "weekends", I assumed 6 track days, which was even more stunning.

BTW: If you go with Carbotech, you don't have to swap rotors, you just change pads. Very convenient.
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Old 09-17-2012, 04:49 PM   #9 (permalink)
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Re: Brake fade on the track

Okay, I started the car and pushed really hard on the brake. There was a long travel with virtually no resistance, but when the pedal stopped it did not move any further. The pedal travel was over half way to the floor, but not all the way to the floor. I am concerned that pedal went so far with no resistance. Would boiled fluid cause the pedal travel or would the pedal feel squishy as the pedal got farther down.

I did take the car out on the road yesterday and did some hard (for a beginner) braking on a country road. The brakes had good grab and took me from 60 mph to 20 very fast, but I only did 6 or 8 hard braking runs. Also, the car did not pull either way under hard braking.

I know that HP Plus are not true race pads, but as several have said, I do not brake as hard as an experienced driver. These pads have been on the car for one weekend (7 - 20 minute sessions)at Autobahn (very hot July temps) and less than 2 sessions at Road America(much cooler temps). I also have done a little street driving, but not a lot. Could the pads possibly be worn out that quickly? Would the high temps in July have caused them to wear faster than normal?
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Old 09-17-2012, 08:14 PM   #10 (permalink)
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Re: Brake fade on the track

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Originally Posted by Klucius View Post
Okay, I started the car and pushed really hard on the brake. There was a long travel with virtually no resistance, but when the pedal stopped it did not move any further. The pedal travel was over half way to the floor, but not all the way to the floor. I am concerned that pedal went so far with no resistance. Would boiled fluid cause the pedal travel or would the pedal feel squishy as the pedal got farther down.

I did take the car out on the road yesterday and did some hard (for a beginner) braking on a country road. The brakes had good grab and took me from 60 mph to 20 very fast, but I only did 6 or 8 hard braking runs. Also, the car did not pull either way under hard braking.

I know that HP Plus are not true race pads, but as several have said, I do not brake as hard as an experienced driver. These pads have been on the car for one weekend (7 - 20 minute sessions)at Autobahn (very hot July temps) and less than 2 sessions at Road America(much cooler temps). I also have done a little street driving, but not a lot. Could the pads possibly be worn out that quickly? Would the high temps in July have caused them to wear faster than normal?
Even baked fluid would still work when cold as in your street test, and retain a good feel when cold. You cannot really replicate track time on the street. You can heat pads up, I suppose, as in a bed-in process.

I think what you have is street pads and good fluid. At this point, I'd get Hawk track pads and put them on right before your next track day if it's this year.. Bed them in per Hawk (if they say use new or lightly turned rotors, then do it - I assume you could use Hawk pads without a new rotor)... Bed them in per their recs then drive them at track. If you can do it, bleed brakes too, couldn't hurt. But I bet your fluid is fine based upon your assumed driving level (no offense). That's good fluid.

Street pads will completely leave you at the track. I've experienced it in turn 5 at RA and thank the track-designer for the turn out there. I really don't see how you could have baked your fluid with your set-up, fwiw.

Pedal travel when first starting up (very first pump) is hard to read. If you pump it once or twice and it's firm, I would think that would seem normal.

"worn out" pads can be measured. Measure them. I bet you have tons of pad. They just don't work when hot, because they are made to work when cold. If you find a pad that works great in both temps, you've found something. Carbotech XP8 are close.
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Old 09-18-2012, 10:38 AM   #11 (permalink)
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Re: Brake fade on the track

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"worn out" pads can be measured. Measure them. I bet you have tons of pad. They just don't work when hot, because they are made to work when cold. If you find a pad that works great in both temps, you've found something. Carbotech XP8 are close.
I run XP10 front and XP8 rear. They do a great job and are not bad around town either. The dusting (in my opinion) is less than the stock pads that came in the car. There will be a little noise under light, cold braking puttering around town but you can either just do more compression braking or just brake later / harder for that traffic light. I don't worry about the noise, it's just the car crying that you haven't taken it to the track frequently enough.


I had purchased the above pads for the track and also a set of the 1521 (Bobcat) pads for street use thinking the dust from the track pads would be excessive. I used the 1521 pads to bed in new rotors, then switched to prebedded (recommended) XP10/8 pads for the track. I was so pleased with the performance of the XP10/8 pads on the street that I never put the 1521 pads back in and sold them with only about 100 miles of use on them.

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Old 09-18-2012, 03:18 PM   #12 (permalink)
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Re: Brake fade on the track

I ran XP8 front/rear for several years. If you can handle the occasional bit of noise, you really can go from street to track with them for quite a while before you'll start needing more brake or more cooling.

The best part is Carbotech brake dust is non corrosive. As you can see in the spherical bearing thread, my control arms still look like new after years of serious use and countless sets of pads. Same deal with my street wheels.
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Old 09-22-2012, 04:16 PM   #13 (permalink)
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Re: Brake fade on the track

I was talking to friend that works on cars. He mentioned pad taper as a possible cause, but he did not know enough about to know if it could cause this type of problem. Can somebody explain to me what pad taper is? If it could cause the brake fade? And how I can check to see if that is a problem.

If it is not pad taper, it sounds like most of you think it is either bad fluid or worn pads. Is there anything else I should check before replacing these two items?

Thanks again for all the information. I don't know how people got anything solved before the Internet and great forums like this.
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Old 09-23-2012, 03:17 PM   #14 (permalink)
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Re: Brake fade on the track

Here's a picture of a pad with a length wise taper. Note how thick the left end of the upper pad in the picture is compared to the other end. Pads can also taper in the other axis. A little bit of taper like this causes a little bit longer pedal, but not much.



This was caused by caliper guide bolts that were slightly bent and binding. The picture also gives you a good idea how hot even ducted brakes get under hard use with track pads. I normally get two days out of these.
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Old 09-26-2012, 04:25 PM   #15 (permalink)
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Re: Brake fade on the track

I had the EXACT same problem until I had the fluid flushed by a race shop and replaced.
Running PIR(portland, or) and going into turn1 at 135 but ending up in the chicane.. yeah. while still at the track, I would ranger method the fluid in the resevior after every session and after session 2, the fluid was still boiling in the paddock..

don't underestimate the value of good fluid. I flush it every season now. You'd be surprised how shitty the dot4 gets after a year of racing.

plus you could step your pads up as everyone else is saying.
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