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-   -   Brake Fade -- looking for budget solution to track problem (http://forum.e46fanatics.com/showthread.php?t=949276)

djmcmath 10-08-2012 06:20 AM

Brake Fade -- looking for budget solution to track problem
So I'm having some problems with brake fade at the track, and am looking for a way to stave off the fade for just a little bit longer, or possibly diagnose something I'm doing wrong.

Here's the story:
Track Day #1: I go out on street tires with (almost) stock brakes. I flushed ATE Super through the system the week before, when I replaced the rubber hoses with braided metal ones. Brakes faded part way through the third session; not horrible, just mushy enough to concern me. They hadn't cooled enough by the 4th session to go back out, so I aborted the last session. Brakes were responding normally half an hour after I left the track.

Track Day #2: Installed slotted rotors and Mintex Extreme pads, bled with Amsoil's brake fluid. I go out on street tires and fade isn't evident until halfway through the last session. Not too bad.

Track Day #3: Bled with Amsoil again, shifted over to slicks (tired of chewing up my street tires). Added ghetto-style brake ducts (2" silicon tubing from front bumper to the inside of the rotor). Fade started early in the 3rd session. There was a long break between sessions 3 and 4, so they weren't terrible in the 4th session, but ... the pedal was a lot softer than I like. Drove home, then drove back out to the track the next morning -- pedal STILL mushy. I ran the first session (wet track) on street tires, slowly, and the brake fade wasn't really an issue because we were all moving so slowly. Second session was dry track, and the pedal was nearly to the floor. Bad. So I pitted in an aborted the rest of the day.

Glazed pads? Inadequate pads? Bad master cylinder? Overheated the fluid and destroyed it, and just need to flush better fluid through it? Just too much extra force from running on slicks, and the brakes can't hack it? 2" brake ducts not quite enough?

Open to ideas here. It's not urgent -- I'm not going back to the track until the spring. But I'd like to start working towards a solution to this thing. Losing track time (that I've paid for!) because my brakes can't hack it is painful.


subieworx 10-08-2012 06:42 AM

The big question is how did the pedal feel on the first couple fade events? Was it soft with no stopping power or was it hard with no stopping power? Each are signs of fade, just in different areas. A soft pedal with no stopping power is fade of the fluid in that you have gotten the fluid too hot and are boiling it. The second is fade of the pad.

The first couple sound more like pad fade whereas the last sounds like fluid fade.

djmcmath 10-08-2012 04:38 PM

Subie -- thanks for the answer, that's some good diagnostics.

Details of "fade": The pedal feels soft, but if I push harder, I can still get stopping power. As the session continues, the fade gets worse, in that I have to push harder to get the same kind of stop. If I pump the pedal, it gets a little better with each successive pump of the pedal. The symptoms typically disappear within an hour or two of leaving the track. Saturday night, after fading pretty hard in the 4th session, symptoms persisted until the next morning (more than an hour of freeway driving later and a night outside in 50F (10C) ambient).

If I'm boiling the fluid, then I need to keep my brakes cooler, so improve my ducting? And switch to a different brake fluid? (Amsoil wet/dry boiling numbers are 410F/580F, which seems like it should be more than adequate, and within a few degrees of ATE Super's points.) Do different brake pads transfer heat differently, or is switching pads likely to be a dead end?


subieworx 10-08-2012 07:59 PM

That definitely sounds like fluid fade and that fluid should be adequate although I have never personally used it.

How many track days have you done? I have done a lot of on track instructing over the years and find that new drivers have much more problems with fade than seasoned drivers as they use the brakes half as hard as they should for twice the distance which builds a ton more heat than using brakes properly.

lucky_doggg7 10-08-2012 09:12 PM

Stop using ATE Super Blue or the equivalent gold colored fluid. This brake fluid does not get the job done. If you are serious, use Motul 600 and your fade problems should go away. As for pads, find a copy of Grassroots Motorsports, the October 2011 issue where James Clay (Owner) of Bimmerworld did a very nice test of seven brands of brake pads. I prefer Porterfield, which ranked well in the test, and I also like very much Pagid, which is THE Porsche Motorsport pad.

Minnoe07 10-09-2012 02:31 AM

As a reference, I use ATE super blue racing fluid, braided lines, hawk ht-10 racing pads front and back, and BMW Motorsport "2 peice rotors" cross drilled up front and a performance directionally vaned cross drilled rotor in the back. Since I switched to this setup, I have not had any fade issues driving in the mountains, Carolina Motorsports Park, or Atlanta Motorsports Park. I am also supercharged so i would have more braking to do than you would. AMP has a pretty fast back straight where you are braking from 120+ mph to about 30-40 mph.

I would also suggest, like previously mentioned, relearning braking zones and proper techniques there so that you are not over working your brakes.

djmcmath 10-09-2012 05:00 PM

Subie - I've only done the 3 days I mention above, so I admit to being an amateur. Further, I know I'm not braking as efficiently as I could be, you're absolutely right. I guess you're suggesting that the real solution is to just brake smarter? I like it - totally fits my budget. :)

Minnoe - thanks for the data point. It's encouraging to know that someone with more power can stop effectively without a significantly more costly system than mine.

Should I be concerned about the "pumping" of the pedal, or the long recovery time?


subieworx 10-09-2012 07:03 PM

The pumping of the pedal and long recovery time are normal when that happens. Often the only way to fix it is to bleed the brakes. I would not be concerned.

As far as your braking technique one thing I always like to teach to my students is to use the full effectiveness of the brakes. Most people are so used to driving on the street that they don't actually know what their brakes are capable of and such don't brake hard enough on track. The exercise I use to teach them how to get used to braking on track after they are used to braking too easily on track is to have them keep the braking point the same , as most people are worried they won't make the corner hence the early braking, and to simply mash the pedal as hard as possible until engaging abs. This will result in the car over slowing and stopping much more quickly then they are used to. After a few times of doing this they realize the brakes have plenty to slow they car and we start pushing the brake point further.

As a means of comparison. I often track my 335 when I don't feel like taking my race miata. It makes 400 whp and weighs 3500 pounds. Much more power and much heavier than I would assume of your car. I run stock brakes entirely except with hawk hp+ pads and motul rbf600 fluid and rarely have issues.

teamdfl 10-09-2012 09:19 PM

Use less brake. You are driving too slow.

djmcmath 10-10-2012 06:31 AM

Wow, ok. Thanks for the wisdom. I'll bleed my brakes and change my driving style. Next time out, I'll try your technique to push the limits and see if that fixes my "brake too early but not hard enough" problem. :)


jared_wiesner 10-10-2012 07:43 AM

A lot of whats been posted above may not be the advice you need to hear. I can't run ATE Super Blue on the track in my car and I brake quite late and very hard. I boil the fluid in the matter of a couple laps. A switch to Pro Speed RS683 brake fluid + the addition of ducting has cured this. A good driver can fade the brakes in no time if your driving hard enough. Sure, I could baby the car and make the brakes last, but then I wouldn't be enjoying myself or getting the most out of the car.

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