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      01-18-2016, 04:33 PM   #1
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Z4M brake fade at track

Hey guys, I experienced some brake fade at the track last summer and I recall coming across a thread (either here or on another forum) where someone mentioned that a couple of the safety systems (hill assist and brake drying) on the car affected braking performance on the track. I can no longer find the thread through extensive google searching. Is anyone familiar with this? Or am I imagining reading this???

As some background info, I had very new OEM front rotors with some time driven with OEM pads. I switched to HP plus pads for track and followed proper bed in procedures. Rear rotors are also OEM, although with more wear and again, using OEM-spec pads on the street with HP plus swapped in for track use. Brake fluid is ATE typ 200 flushed within a couple weeks of the track day.

Since swapping the OEM-spec pads back on for road duty, I now notice blue-ish deposit on the front rotors - and from what I have read this could be due to using two different brands of rotors - I am wondering this could have lead to the fade?

Any insight is greatly appreciated!
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      01-18-2016, 04:52 PM   #2
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What sort of "fade" did you experience? Is it fluid (pedal goes soft, car slows down but foot goes to floor) or pad (pedal pressure is fine, car barely slows down even though you're trying to punch a hole through the floorboard)?

Blue tint on the rotor after track use is NORMAL.
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      01-18-2016, 04:55 PM   #3
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Definitely pad, pressure was fine but didn't scrub enough speed as normal
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      01-18-2016, 05:11 PM   #4
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Then we can probably rule out Hill Start Assist. Hill start assist MAY force the pad into contact with the hot rotor when you park in the paddocks, especially if there's an incline as you shut down the car with foot on the brakes and car in gear. It will result in heat transfer from pad to caliper piston to fluid, slowly boiling the fluid inside the calipers leading to the "soft pedal" fluid fade.

The brake drying feature CAN result in unnecessary heat built up, but unlikely. The brake drying feature barely brushes the brakes every few seconds to sweep water off of the rotors. It's on only if you leave both your headlights on auto and wiper on auto (right stalk up one position). It does drag the brakes hard enough to feel if you're on top end track pads and r-comps, but in the course of a 20-25 min session it SHOULDN'T generate enough heat to fade brakes. But if you're feeling pad fade, THIS, of the two features, would cause that.

Check and see if you have your right hand stalk up one and on auto. If you do, disable for track use, and disable automatic headlights. This will deactivate the brake drying feature (since both off would indicate sunny and dry condition).

And if you're still fading, then the culprit are the brake pads or lack of cooling for the speed you're carrying.
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      01-18-2016, 05:27 PM   #5
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We can rule out the brake drying feature as well, as I never use auto headlights or wipers.

I will start with removing the factory ducts come spring time. Would you recommend a more robust brake fluid? RBF660?

I just saw your comment about the blue tint - I failed to mention earlier than I get a slight vibration under medium (~50mph) to high speed braking since the last track day - should I start with an alignment? I'll post a pic of the rotor this evening after work.

Thanks again!
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      01-18-2016, 05:54 PM   #6
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Quote:
Originally Posted by Shorts View Post
We can rule out the brake drying feature as well, as I never use auto headlights or wipers.

I will start with removing the factory ducts come spring time. Would you recommend a more robust brake fluid? RBF660?

I just saw your comment about the blue tint - I failed to mention earlier than I get a slight vibration under medium (~50mph) to high speed braking since the last track day - should I start with an alignment? I'll post a pic of the rotor this evening after work.

Thanks again!
More robust fluid...Yes, but it's not going to cure your brake fade. Especially if, as you said, the pedals are firm but the car's not slowing down. I'd start with the pads, IMO. This car has enough HP to generate enough heat in the brakes that requires something along the lines of Hawk DTC-60s or Cobalt XR-3s or PFC-0X/11. I "personally" would do both, upgrade the fluid to higher end racing fluid AND track pads for that extra margin of safety.

The blue tint is from the material of the rotor heating up and cooling down rapidly, same reason why titanium exhaust tips are blueish purple (except, now-a-days it's done on purpose), it's not deposit. Deposit will show up a dark muddy grey splotches or streaks on the rotor.

The symptoms you describe re: braking sounds more like normal deposit, which is exacerbated by rotors with holes in them, because the edges of the holes catch pad material and leaves behind slight ridges, especially if the rotors are hot enough to MELT pad material.

Here's another question. Did this fade show-up early in the first couple of sessions, or did it show up as you progressed through the day? Like in session 3 or 4? And my next question is, how are you doing your cool-down laps? Do you try and go through an entire lap driving at speed (not coasting) while not touching the brakes?

The reason I ask, and I'm going to explain it anyway whether you answer or not, is because if you're doing 4-5 sessions a day, even if they're spread out throughout the day, there's heat trapped in the rotors that never fully dissipate while you're in the paddocks. Say, after session 1 you come in to the pit with the rotors relatively warm at 300F. It sits for 1.5 hours and radiates heat and cools off down to 200 before you go out for session 2. Session 2 builds on top of that heat, and you come off the track at 375F, and before you go out for session 3 your rotors are still at 275...You get my drift? By session 4 your rotor temp, before you head out, is already significantly above ambient.

I would get an infrared laser thermometer, and measure your brake rotor temp if you're experiencing fade in the latter half of the day, and see if the temp of the rotor is the same before you go out. If it's significantly higher than previous sessions, then I would extend the cool down lap longer and attempt to drive the cool down lap without engaging brakes at speed.

Or get bigger/better rotor and more cooling.
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      01-18-2016, 07:36 PM   #7
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Quote:
Originally Posted by The HACK View Post
The reason I ask, and I'm going to explain it anyway whether you answer or not, is because if you're doing 4-5 sessions a day, even if they're spread out throughout the day, there's heat trapped in the rotors that never fully dissipate while you're in the paddocks. Say, after session 1 you come in to the pit with the rotors relatively warm at 300F. It sits for 1.5 hours and radiates heat and cools off down to 200 before you go out for session 2. Session 2 builds on top of that heat, and you come off the track at 375F, and before you go out for session 3 your rotors are still at 275...You get my drift? By session 4 your rotor temp, before you head out, is already significantly above ambient.

I would get an infrared laser thermometer, and measure your brake rotor temp if you're experiencing fade in the latter half of the day, and see if the temp of the rotor is the same before you go out. If it's significantly higher than previous sessions, then I would extend the cool down lap longer and attempt to drive the cool down lap without engaging brakes at speed.

Or get bigger/better rotor and more cooling.
Great info.
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      01-18-2016, 08:09 PM   #8
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Originally Posted by Finnegan View Post
Great info.
And I concur.
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      01-18-2016, 10:43 PM   #9
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Quote:
Originally Posted by The HACK View Post
More robust fluid...Yes, but it's not going to cure your brake fade. Especially if, as you said, the pedals are firm but the car's not slowing down. I'd start with the pads, IMO. This car has enough HP to generate enough heat in the brakes that requires something along the lines of Hawk DTC-60s or Cobalt XR-3s or PFC-0X/11. I "personally" would do both, upgrade the fluid to higher end racing fluid AND track pads for that extra margin of safety.

The blue tint is from the material of the rotor heating up and cooling down rapidly, same reason why titanium exhaust tips are blueish purple (except, now-a-days it's done on purpose), it's not deposit. Deposit will show up a dark muddy grey splotches or streaks on the rotor.

The symptoms you describe re: braking sounds more like normal deposit, which is exacerbated by rotors with holes in them, because the edges of the holes catch pad material and leaves behind slight ridges, especially if the rotors are hot enough to MELT pad material.

Here's another question. Did this fade show-up early in the first couple of sessions, or did it show up as you progressed through the day? Like in session 3 or 4? And my next question is, how are you doing your cool-down laps? Do you try and go through an entire lap driving at speed (not coasting) while not touching the brakes?

The reason I ask, and I'm going to explain it anyway whether you answer or not, is because if you're doing 4-5 sessions a day, even if they're spread out throughout the day, there's heat trapped in the rotors that never fully dissipate while you're in the paddocks. Say, after session 1 you come in to the pit with the rotors relatively warm at 300F. It sits for 1.5 hours and radiates heat and cools off down to 200 before you go out for session 2. Session 2 builds on top of that heat, and you come off the track at 375F, and before you go out for session 3 your rotors are still at 275...You get my drift? By session 4 your rotor temp, before you head out, is already significantly above ambient.

I would get an infrared laser thermometer, and measure your brake rotor temp if you're experiencing fade in the latter half of the day, and see if the temp of the rotor is the same before you go out. If it's significantly higher than previous sessions, then I would extend the cool down lap longer and attempt to drive the cool down lap without engaging brakes at speed.

Or get bigger/better rotor and more cooling.
Interesting point on the brakes getting progressively hotter each session. The fading happened in the 3rd session - it was my final session since I went off track (into gravel thankfully) and spooked myself enough to skip the final two sessions of the day.

On cool down, I barely use the brakes but sometimes brush the pedal by habit.

Please see below a couple of pics I took of the rotors - not sure if the lighting is appropriate enough to determine whether the deposits are problematic?

Looks like I have some homework cut out for me before springtime to research which pads to get and the best way to create a better duct! I find it very hard to accept that this car needs a bbk so I exhaust (no pun intended) all possibilities before I come to that conclusion!

https://goo.gl/photos/GAWbBTFNtYQwBVHj8

https://goo.gl/photos/513NZ7sBxrdGH8en9
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      05-15-2017, 07:02 PM   #10
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Quote:
Originally Posted by The HACK View Post
More robust fluid...Yes, but it's not going to cure your brake fade. Especially if, as you said, the pedals are firm but the car's not slowing down. I'd start with the pads, IMO. This car has enough HP to generate enough heat in the brakes that requires something along the lines of Hawk DTC-60s or Cobalt XR-3s or PFC-0X/11. I "personally" would do both, upgrade the fluid to higher end racing fluid AND track pads for that extra margin of safety.

The blue tint is from the material of the rotor heating up and cooling down rapidly, same reason why titanium exhaust tips are blueish purple (except, now-a-days it's done on purpose), it's not deposit. Deposit will show up a dark muddy grey splotches or streaks on the rotor.

The symptoms you describe re: braking sounds more like normal deposit, which is exacerbated by rotors with holes in them, because the edges of the holes catch pad material and leaves behind slight ridges, especially if the rotors are hot enough to MELT pad material.

Here's another question. Did this fade show-up early in the first couple of sessions, or did it show up as you progressed through the day? Like in session 3 or 4? And my next question is, how are you doing your cool-down laps? Do you try and go through an entire lap driving at speed (not coasting) while not touching the brakes?

The reason I ask, and I'm going to explain it anyway whether you answer or not, is because if you're doing 4-5 sessions a day, even if they're spread out throughout the day, there's heat trapped in the rotors that never fully dissipate while you're in the paddocks. Say, after session 1 you come in to the pit with the rotors relatively warm at 300F. It sits for 1.5 hours and radiates heat and cools off down to 200 before you go out for session 2. Session 2 builds on top of that heat, and you come off the track at 375F, and before you go out for session 3 your rotors are still at 275...You get my drift? By session 4 your rotor temp, before you head out, is already significantly above ambient.

I would get an infrared laser thermometer, and measure your brake rotor temp if you're experiencing fade in the latter half of the day, and see if the temp of the rotor is the same before you go out. If it's significantly higher than previous sessions, then I would extend the cool down lap longer and attempt to drive the cool down lap without engaging brakes at speed.

Or get bigger/better rotor and more cooling.
Was doing some search on 'fade' in the forums when I came across this. I tracked the car today at Thompson Speedway in CT for a solid 4 sessions throughout the day. It rained for the first two, and my wipers and lights both were on auto. Track remained wet for the other two sessions, obviously. I had no clue about the auto drying feature built into our cars.

Sessions 3 and 4 are when I experienced really heavy brake fade - especially entering corner 1 after a long, fast straightway and then subsequently in the next 3 corners. It felt to me like fluid, since the pedal was getting 'cushiony' and traveling further than expected. Pads and fluids were both replaced last weekend with ATE 200 and Hawk HPS 5.0

Anybody else also experience this? My instructor guessed that the fade was probably due to boiling fluid caused from the increased friction of performance pads. These aren't even race pads, though, so not sure if I should expect worse from DTC grade Hawk pads?

I have a BBK on order, but curious to see if others have been experiencing this with the stock setup too.
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      01-15-2019, 10:01 PM   #11
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Fellas,

I'm gearing up for at least one track day this spring and after some thorough research in this forum and some other googling bought a set of DTC-60 front and rear. I'm planning on using RBF600 fluid as well.

What are thoughts on buying a set of rotors to use solely with the DTC-60 and keep the current rotors for the street oem-grade pads? I'm wondering if I should be concerned with pad deposits on the rotors?
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      01-16-2019, 04:04 AM   #12
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I'm working on a 3D-printed funnel for the Z4 M front bumper to cool the brakes, will throw up a thread in the classifieds when I'm done with it.
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      01-16-2019, 08:02 AM   #13
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Quote:
Originally Posted by Shorts View Post
Fellas,

I'm gearing up for at least one track day this spring and after some thorough research in this forum and some other googling bought a set of DTC-60 front and rear. I'm planning on using RBF600 fluid as well.

What are thoughts on buying a set of rotors to use solely with the DTC-60 and keep the current rotors for the street oem-grade pads? I'm wondering if I should be concerned with pad deposits on the rotors?
I use DTC-60 pads front and rear as well with stock rotors. I find the 'cold' braking driving to and from the track cleans off the pad deposits so I don't experience any braking issues or vibrations. These pads are quite aggressive when cold so by the time I get home I can swap back to OE pads.
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      01-16-2019, 11:23 AM   #14
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I'm working on a 3D-printed funnel for the Z4 M front bumper to cool the brakes, will throw up a thread in the classifieds when I'm done with it.
Awesome, looking forward to it
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      01-16-2019, 11:25 AM   #15
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Quote:
Originally Posted by rockstar93 View Post
I use DTC-60 pads front and rear as well with stock rotors. I find the 'cold' braking driving to and from the track cleans off the pad deposits so I don't experience any braking issues or vibrations. These pads are quite aggressive when cold so by the time I get home I can swap back to OE pads.
Thanks for the input - I'll try this as well
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      01-16-2019, 02:52 PM   #16
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Quote:
Originally Posted by Shorts View Post
Fellas,

I'm gearing up for at least one track day this spring and after some thorough research in this forum and some other googling bought a set of DTC-60 front and rear. I'm planning on using RBF600 fluid as well.

What are thoughts on buying a set of rotors to use solely with the DTC-60 and keep the current rotors for the street oem-grade pads? I'm wondering if I should be concerned with pad deposits on the rotors?
Good feedback from the others. If you're only doing a couple track days, no need to get another set of rotors or install cooling upgrades. The DTC-60 is a great pad with good pedal modulation and fresh 600 fluid will help you with fade. Cheap insurance is to bleed your fluid before every event.

Also, like others have noted, you can drive on the street with the DTC-60. I wouldn't recommend it for extended periods of time because the cold pad will be hard on your rotors and not stop well until heat is built up. Have fun!
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      01-17-2019, 03:07 AM   #17
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I've done funnels for Z3 (standard bumper), E36 M-Sport/M3, E30 M3 EVO III and currently working on the Z4 M. I do brake shields and funnels for those to. Everything is done to be bolt on, no modification or cutting required. You can find pictures on my instagram: https://www.instagram.com/andre_westersund/
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