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Suspension | Chassis | Brakes -- Sponsored by 949 Racing Relating to suspension, chassis, and brakes. Sponsored by 949 Racing.


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Old 05-12-2015, 01:03 PM   #1
ubernostrum
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Brake pad not positioned correctly?

I am running the AP Sprint kit and I have an issue with my brake pads that I am trying to figure out. These are XP10 front pads after 2 track days. (National Corvette Museum and Atlanta Motorsports Park)
Notice on the left pad the raised inner edge.


Here is a better look at it.


This is happening on the inner pad on both the driver and passenger sides. It looks to me like the pad is overhanging the inside edge of the rotor on that side. I think this is also contributing the the 'effing loudness of the brakes. They squeal like none-other. The instructor that was showing me the line at AMP had to ask if my brakes were ok. Coming into the pits everyone looks, cause there is no way you can ignore it. The only time they don't sound like a terminally injured helicopter is when I'm deep into the brake pedal on the track with them warmed all the way up. I will say that the braking performance has not been effected, and has been consistent and great every session.

I cant think of any way to adjust the position of the pad in the caliper to move it fully onto the rotor surface. Or did I install it wrong? It was pretty straightforward and nothing that I have seen talks about adjusting the caliper positioning, that would have been done by the bracket design and is the whole reason to by a pre-made kit.

The 1521 pads I use on the street look to be doing the same thing. But without the noise, and the raised part of the pad is not nearly as noticeable since there hasn't been as much wear on the street pads.

I overheated the pads and smeared them. AMP has 2 really hard braking zones that contributed, I had no smearing after NCM. But the smearing(and thus the heat) is located only on the outer end of the rotor, which would make me think the brake force isn't being distributed evenly.



Any thoughts on what is going on?

Pedal dance on most of the sessions, but not all.
AP Sprint BBK, Carbotech XP10 pads front and rear for track, Carbotech 1521 for street
Direzza ZII SS 235-40-17
1.5 front, 2.5 rear neg camber
0 front and 1/8in rear toe in
RCE Yellow springs, SPL rear lower control arms, SPL rear toe arms, camber bolts in the front.
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Old 05-12-2015, 02:13 PM   #2
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Lip is normal so you can just grind it down. The radial depth from pad manufacturer to pad manufacturer is different for the D41. Sometimes it can be D42, D39, D40.5, etc.

I can see that the pads are starting to glaze ever so slightly as well. You are overheating the pads which also may mean you could be engaging ABS and heating up the brakes more than they should. XP10 on the AP Sprint Kit is pretty solid especially for your setup.

The brakes aren't bedded in properly as well. If they were, then the brakes will be pretty silent. Also note that Carbotechs do make insane banshee squeals and sometimes feel like they are grinding. It's somewhat of a CT trademark too. Try cleaning up the pads a bit and re-bed the brakes. Stay off of ABS.
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Old 05-12-2015, 02:26 PM   #3
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If you have any videos or datalogs of your driving, please post them, so that I can further dig into why you're overheating your pads that badly.

Were these new pads mated to new rotors?
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Old 05-12-2015, 04:16 PM   #4
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I wish I had some logging or video, but I do not have that ability. I do remember having an oh-shit moment and did 115mph to 30mph all on the ABS, but other than that I only remember getting into the ABS for a second or so a couple of times that day when getting a little too aggressive with the braking.

The pads were bedded at the track during the first session of the day. I swapped them when I arrived that morning and had no time to do it properly.
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Old 05-12-2015, 04:54 PM   #5
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Originally Posted by ubernostrum View Post
I wish I had some logging or video, but I do not have that ability. I do remember having an oh-shit moment and did 115mph to 30mph all on the ABS, but other than that I only remember getting into the ABS for a second or so a couple of times that day when getting a little too aggressive with the braking.

The pads were bedded at the track during the first session of the day. I swapped them when I arrived that morning and had no time to do it properly.
You'll basically have to sacrifice your first session of the day to bed them in properly. The improper transfer layer spread on the rotor causes some inconsistent performance and wear.
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Old 05-12-2015, 06:01 PM   #6
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Originally Posted by ubernostrum View Post
I wish I had some logging or video, but I do not have that ability. I do remember having an oh-shit moment and did 115mph to 30mph all on the ABS, but other than that I only remember getting into the ABS for a second or so a couple of times that day when getting a little too aggressive with the braking.

The pads were bedded at the track during the first session of the day. I swapped them when I arrived that morning and had no time to do it properly.
Can you list all of the speeds you see at your track for each braking zone? E.g. 115 to 40, 60 to 40, etc? Also, what is the length (time) of your laps, and what kind of tires are you using?
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Old 05-13-2015, 01:10 PM   #7
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Quote:
Originally Posted by CSG Mike View Post
Can you list all of the speeds you see at your track for each braking zone? E.g. 115 to 40, 60 to 40, etc? Also, what is the length (time) of your laps, and what kind of tires are you using?
Track map, It is one of my favorites with lots of elevation change
http://www.atlantamotorsportspark.co...n_%20track.pdf

According to Harry's Lap Timer and the 1Hz GPS on my phone, my best of the day was a 1:39.35, By the end of the day I was consistently running in the low 1:40s with a number of laps breaking into the 1:39s. I had 5 25 min sessions, first lap of each was at a less intense pace to warm everything up.

T1 and T6 at AMP have the hardest braking zones. T1 is a 5th to 2nd downshift, and T6 is 4th to 2nd.

T1 I was going into the braking zone at 110-115, My speed on the straight leading into it kept getting faster as I learned the track and got brave enough to not lift on T15/16. Exit of T1 was 30-35mph. I felt I could carry more speed on the exit however, I found myself driving to track-out instead of ending up there naturally.

For T6 going into the braking zone was more varied as I was trying a lot of different things with the T4 carousel turn before it. Early in the day I was topping out 3rd gear when I got on the brakes, later I was into 4th, 80-85mph. Exit was 30-35 mph.

The other braking spots are:
T3, 4th to 3rd downshift, 75 in, 45 out
T10, stay in 4th, 85 in, 55 out
T11, 4th to 3rd downshift, 60 in, 40 out, I could have carried more speed here.
and a quick stab at T12 to settle the car and help turn-in.

Speeds are from HLT, but i'm not sure how accurate they are. The speedo seemed to be 5mph faster than the app indicated. The numbers are pulled from my best lap.

I am on Direzza ZII star spec in 235/40/17 size. Tires were on their 2nd track day and feeling pretty good.

ATL BRZ has some good video of the track.
http://www.ft86club.com/forums/showthread.php?t=13157

Last edited by ubernostrum; 05-13-2015 at 01:13 PM. Reason: typo
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Old 05-13-2015, 01:42 PM   #8
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That braking is fairly light, except for the hard, slightly downhill zone into T1. THat's nearly as rough as Laguna Seca, and that T1 is what is causing your brakes to get so hot.

Try using a higher temp pad next time around, to help mitigate that huge heat spike at T1.

This is assuming you're not sitting on ABS.

You *are* overheating the pad, but not terribly. The pad life indicates that the rate of wear is pretty good.
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Old 05-14-2015, 02:36 PM   #9
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Quote:
Originally Posted by CSG David View Post
Try cleaning up the pads a bit and re-bed the brakes.
How should I go about cleaning up the pad? I could take a file to the raised part, but what do you do with the shiny glazed section of the pad?
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Old 05-14-2015, 02:55 PM   #10
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How should I go about cleaning up the pad? I could take a file to the raised part, but what do you do with the shiny glazed section of the pad?
Use a file. The ultra ghetto method to kind of "rough up" the pad is to use the pavement. The other technique is to drive around in the cold and allow the pad and rotor to scrape itself clean.
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Old 05-14-2015, 06:01 PM   #11
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Swapping pads leaves disk surface impregnated with micro layer of pad material from the old pad that can lead to the glazing. Also can lead to squeal and erratic breaking for a short while. My track pads squeal until up to temp.
I use a belt sander to remove glaze and 3M makes a small sanding head to burnish the rotor.
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