03-28-2017, 03:46 PM | #1 |
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Clogged drilled rotor holes causing fade on track?
Hey everyone.
My pagids worked great on my first two track days, but I started to get some fade on my third. I'm running Castrol SRF, so I don't think it's the fluid. I am a rather aggressive braker, and I'm getting up to 140mph on Summit's straight before slamming down to 45mph at the limit of my Pilot Super Sports. I noticed that the cross drilled holes in my factory discs were plugged with brake dust, so I'm wondering if a hot disc is the the source of the fade. I would have had to punch every single hole on each disc to test and didn't have any compressed air to blow them out to test this theory. Have you guys had issues like this on your cars or other M cars, or is this even an issue? Thanks. |
03-28-2017, 04:02 PM | #2 |
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You may need to re-bleed your fluid, which pagids? I haven't had fade with RSL1's and RBF600. The clogged holes won't contribute to overheating or performance, just blow them out when you wash the car.
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03-28-2017, 05:51 PM | #3 |
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RS29's.
I filled right below the Max line when I originally bled the brakes bc I figured there would be some expansion. I did see a little fluid on the top of the reservoir after my run, so maybe there's more fluid expansion than I anticipated? Even if a little fluid is pushed out of the reservoir, it shouldn't introduce any air into the lines, correct? Thanks. |
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03-28-2017, 06:37 PM | #4 |
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how old is the fluid?
i ran motul 600 with RS29 pads in my f80 and i experienced imperceptible fade. i would think with the car being a tad lighter, it shouldn't be an issue
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03-28-2017, 08:32 PM | #6 |
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ZM2, I use Motul 600/660 with Carbotech XP 10/8 pads....I have noticed the holes fill up with crud. We run the car on tracks that are hard on brakes, so I installed cooling ducts right away. So far no issues....except once I let a pro driver do 10 minutes of hot laps at Road Atlanta then we pitted and I ran.....had some slight initial fade from sitting still in the pit with hot brakes then going right back out. I have my brakes bled after every event and the shop did comment that the clogged holes could cause a slight increase in temps. I installed AP temp strips on my front and rear calipers , so I can keep an eye on temps.....so far the fronts stay below 400 degrees and the rears 450. Remember this is just the front face of the caliper so it is a relative number, not the actual pad or fluid temp.
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03-28-2017, 09:46 PM | #9 |
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03-28-2017, 10:24 PM | #10 |
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Interesting comments from everyone.
I am running in MDM while I'm learning the limits of the car. I haven't heard anyone complain about the RS29/SRF combo, so it makes me wonder if a perfect bleed job didn't happen. If so, it just seems odd that it didn't appear until my third day. What fluid level do you all start at, and have you noticed any expansion? Thanks. |
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03-29-2017, 09:00 AM | #12 |
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Brake bleeding is not likely root cause, and certainly overfilling it isn't. Lots of guys are realy crazy about brake fluid too, but if things are set up right its not critical. I've always just used either stock or Castrol LMA, even for my race cars. I've never boiled fluid with modern pads either. Driver inputs are the single biggest determinant assuming the base vehicle is maintained and the brake system is appropriate for its use (which it is). Braking hard isn't bad, but breaking kind of hard for a longer time isn't great. As mentioned, having stability/traction control on works stuff pretty hard too.
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03-29-2017, 09:25 AM | #13 | |
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Quote:
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03-29-2017, 09:59 AM | #14 |
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I hear ya on TC & MDM.
This is my first M car, only my third day on a real track (lots of AutoX experience), and I'm remapping my brain on switching from FWD to RWD after 12-yrs of driving JCW MINI's. So, I wanted to work up to turning it off. All that said, I have a good feel for the car now, MDM was very intrusive (although, it seemed more intervention was happening on the rear brakes, vs front), and I was bumped to intermediate very quickly, so I had planned to turn MDM off on the next outing. It'll be some weeks before my next track day, so I'll update everyone then. Thanks for the feedback! |
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03-29-2017, 10:05 AM | #15 |
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Depending on your experience level I completely agree running in MDM mode until you feel comfortable and learn the limits of your new car. I am in the same boat and planning to do the same.
the adverse effect is more intervention and brake overheating if you are pushing the car really hard. My suggestion would be to run 8-9/10th and pay attention when the traction control flickers on the dash so you can actually learn from it and better understand the car behavior prior to removing all nannies. |
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03-29-2017, 01:08 PM | #17 |
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Also, if you have lots of auto-x experience, track is a whole different animal.... Oddest transition is to just slow down your inputs - its rythm, not reaction time which can be quite a transition for auto-x guys. I did auto-x for a many years until I could afford road racing, and haven't been back since!
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03-29-2017, 01:20 PM | #18 |
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Agreed. I'm a solid autox'er, but it got boring and I'm loving the track a lot more.
Both my instructors were telling me I was doing awesome for just a few days on track, but I gotta ditch all those violent autox movements and focus on smoothness and transitions! I definitely see that now, and how autox is likely amplifying my braking issue. So, a real focus on being smooth is my biggest priority right now. A concern I have with TC full off vs MDM is TC off puts steering and throttle response back into sport mode, and I really enjoy the comfort mode setting for steering and throttle with MDM on. Last edited by ZM2; 03-29-2017 at 01:23 PM.. Reason: Clarification |
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03-29-2017, 05:35 PM | #19 |
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You should definitely look into coding....there are at least 25 custom codes you can access including Euro MDM....for about $100. I never tracked with the stock MDM so I can't compare directly , but I have run with the Euro MDM and DSC off and the difference is slight. For those who say I must be "slow", I had Jade Buford ( just won Continental Challenge at Sebring) track in both modes and his lap times were very close, I think less than .5 seconds. Get very comfortable with the car before turning everything off and you will be fine.
Last edited by Twt; 03-29-2017 at 05:45 PM.. |
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03-29-2017, 11:17 PM | #20 | |
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If you are a good autocrosser you probably have decent car control skills and probably at least as comfortable catching a car that's sliding as an intermediate level HPDE driver. When I transitioned from auto-x to track I scared the crap out of my instructor hanging the ass end of my Elise around all the way around the track. He said I was super jerky but said I had better car control than most the instructors. I've since smoothed out my inputs a lot on the track and I still feel comfortable driving just about anything with TC completely off. The M2 is really tame and neutral and you have to do something pretty stupid to get yourself in big trouble. Turn it off, and ramp up your speed slowly, you'll be surprised how good the car is. |
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03-30-2017, 08:47 AM | #21 |
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I'm pretty sure the graphic in the manual shows the steering and throttle response going back to the tight Sport setting when TC is all the way off. I'll double check this weekend when I get back to my car.
If it does go to Sport settings with TC off (too responsive for my liking on the track), my local shop (RRT in Sterling, VA) has a coder that will do Euro MDM for $80. I'll likely also have them flush the brake fluid just to be safe. I'm pretty sure I did a good flush & bleed job, but it was very disconcerting getting fade going into turn 1 at Summit and I want to rule everything out. Based on everyone's feedback, I'll get TC off quickly, but just want to work up to it. Oh, and I also scared the crap out of both my instructors! They both yelled at me when I would kick the back end out under hard braking with a little steering input (mostly, I was doing it for fun and that's how I'd get my MINI to rotate), and in one of my wet sessions I was enjoying spinning up the rears and sliding the car (as much as MDM would let me) and he didn't like that either. It's a super fun car. Just need to turn off the sliding for fun stuff and make it smooth. Thanks for all the input guys. |
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03-30-2017, 01:43 PM | #22 |
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The 2 is a blast to get sideways, BUT even with the DCT off it will limit the slip angle. We could drift my C5Z easily and thought the M2 would do the same ( see commercials) but the background nannies activate. Does anyone know how to remove these as well....we were thinking about disconnecting the rear ABS sensors.....thoughts?
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