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Old 04-08-2011, 04:10 AM   #1
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Default Brake issue

Thought I would try posting here before I tried at mazdaracers.com

I have a 99 spec miata, that I am just sorting out. The car came with new rotors and carbotech XP10 pads.

When cold I have great wheel spin(car in the air, spin a front wheel). There is negligible rolling resistance the wheel will spin between 6-7 revolutions. Now, when I come off the track; pads and rotors hot, it is a different story, the wheel will spin approx 1 time using the same force that nets 7 rotations on a cold set of brakes.

It has been several years since I have raced, and in the past I have always used hawk blues, so I am new to the carbotechs. It looks to me like I may be having some material transferring to the rotor, causing the extra friction and rolling resistance that I have noticed. I may be mistaken, but I don't remember my rotors looking like this when I was running hawk blues. Having a free rolling car is important in all applications, but especially in the low hp world that is spec miata. Any input would be greatly appreciated.

Stock rotors and calipers, pads are free. Calipers are in good shape and slide freely on the locating pins. Here are a couple of shots of the rotors.

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Old 04-08-2011, 09:01 AM   #2
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Looks like material transfer. I would change pads. Free? You get what you pay for.....
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Old 04-08-2011, 09:13 AM   #3
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My XP10s were never painted white...

I'd scotchbrite those rotors and double check the pad surface
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Old 04-08-2011, 11:02 AM   #4
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Free as in open, as in you can run any pad you want.
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Old 04-08-2011, 11:13 AM   #5
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Quote:
Originally Posted by Braineack View Post
My XP10s were never painted white...

I'd scotchbrite those rotors and double check the pad surface
The backing plates were originally silver. I think I will pull the rotors and turn them, then I'll throw on some hawk blues.

Carbotech sways talks about being rotor friendly, but I really could care less about that. Rotors are a consumable in race applications.

Last edited by hingstonwm; 04-08-2011 at 08:44 PM. Reason: to fix stupid auto sprlling on smart phone
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Old 04-08-2011, 08:35 PM   #6
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The backing paint turned white on all my carbotech XP12s on 1.8 front rotors - . I didn't have any unusual performance issues. On the new 11.75" BBK from trackspeed, I didn't notice the paint turning white, but resistance was noted when trying to spin the wheel when hot off track - compared to free spinning when cold. Not sure if it's the kit or the new hubs I installed over the winter. But your rotors don't look any different than mine did with xp12s
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Old 04-08-2011, 08:39 PM   #7
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Rotors don't look so good. Go over them with an 80-grit sandpaper pad on a DA sander and re-bed the pads.
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Old 04-08-2011, 08:52 PM   #8
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Rotors don't look so good. Go over them with an 80-grit sandpaper pad on a DA sander and re-bed the pads.
I need to get to the bottom of the problem, I suspect the resistance I'm feeling is due to material transfer. the first step is to try hawk blue pads with fresh rotors. If this solves the problem, I will just continue to run the hawks. I am curious to know exactly which carbotech pad I currently have, I tried calling them earlier today with no luck, I will try again on monday. It maybe possible that I have a lower performing had on there
Which is resulting in material transfer. The current pads were picked up at the run of this last year.
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Old 04-08-2011, 11:31 PM   #9
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Did you break them in per CT's instructions? They shouldn't do that on a Spec if they were broken in properly.

Blues are a really, really old pad, BTW. The DTC-70 is what I use on the black car and I quite like it. Modulates much differently than the CT, though.
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Old 04-09-2011, 12:57 PM   #10
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Quote:
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Did you break them in per CT's instructions? They shouldn't do that on a Spec if they were broken in properly.

Blues are a really, really old pad, BTW. The DTC-70 is what I use on the black car and I quite like it. Modulates much differently than the CT, though.
Not sure, the pads came on the car when I purchased it. The rotors and pads only had the race at the runoffs on them, I doubt they were broke in properly.

I know blues are old, but they work. I may try turning the current rotors and run the pads again. But I will have a fresh set of rotors and pads to try as well. I love the way these CT's feel, but if they don't roll free they are costing time.

I have 1.8 brakes(obviously), the numbers on the backing plate are xd635, any help would be appreciated.
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Old 04-10-2011, 03:09 PM   #11
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I've never tried rolling my wheels when hot, but Ive never had a problem with Cobalt's, and I've only had good feed back from my customers I sell them to as well. You cant beat the no bedding or braking in of any sort and run it on any rotor with out surfacing them. Just slap them on and go.
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Old 05-01-2011, 11:57 AM   #12
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A lot of very successful spec miata racers are still running blues. Don't let anyone talk you out of them if you're comfortable with them.

I can't see from the pictures you've posted if you are running the "springs" that pull the pads back from the rotors when the brakes are applied. Many throw those away because they're a pain the butt when changing pads, but they DO make a difference in rolling resistance. So, make sure you keep those on!

Cheers,

Dean
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Old 05-12-2011, 02:20 AM   #13
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Dean,

Yeah, I run the springs. They loose tension pretty quickly, I plan on changing them out before every race. They didn't help with the brake drag on the carbotechs. We will see how it goes with the hawks.
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Old 05-12-2011, 03:09 AM   #14
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My carbotech's did the same ****. I went through 2-sets in 2 days. I'd leave the track, make the rotors the nice, blue color to show they're bedded properly, then on the track they'd go to **** every time. I tried going out for 2 laps, then resting for an hour, and I never got it right. I threw on an old set of Hawk blues on the Carbotech'd rotors and never looked back, and enjoyed the rest of the weekend. Sure, Blue's have a bad rap and I run DTC-60 for a reason, but they work every time, no matter how how you get them.

With Hawks (DTC-60 is my favorite) I've never had this problem. There is one track where I can overheat the pad, but I have much bigger rotors now with proper venting and I don't think that will happen again.

You guys can go on and on about how I didn't properly bed the pads, although I followed the instructions and visually confirmed the bedding, on two new sets of rotors. If that's the case then it's too complicated for me. Lots of the Cali guys like those pads and scoff at me, I run my Hawks and smile.
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Old 05-12-2011, 03:38 AM   #15
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With the SM we cant vent the brakes, and we must run the stock calipers and stock size rotors. I just dropped dime on new hawk blues, turned the front rotors and installed fresh rotors on the rear. I know what the blues are capable of and I have never overheated them, though there is not much feedback from blues. I know nothing about the DTC compound, what can you tell me about them when compared to the blues.
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Old 05-12-2011, 09:50 AM   #16
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Quote:
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I know nothing about the DTC compound, what can you tell me about them when compared to the blues.
The blue and the 60's could not be more different. Less bite, less torque-ramp, less pedal pressure required but still much more friction than XP12. They are similar to PFC97 with more general bite but with much more pressure reqired to lock up.
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Old 05-12-2011, 02:04 PM   #17
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i love my carbotechs on the track. they don't overheat, excellent modulation, they even help me heel/toe by not having to use so much pressure causing the brake pedal to be lower than the gas pedal. only issue i have with them is severe squeeking with light pedal pressure on the street. my pads have 4 trackdays on them so far and can barely notice any wear. although the track they've been used at is real easy on brakes. blues literally eat rotors. my buddy had them on his crx and he had to brush of the rotor shards from his wheels after every session. but they did work. if i was gonna switch pads i'd probably try the carbon lorraine's or actually, the less expensive re-labeled version sold here. can't remember the name. i think bbundy used or uses them.
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Old 05-12-2011, 02:17 PM   #18
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I agree with spoolin on the carbotechs. My spec miata had blues on it when I bought it and I couldn't stand how they felt. I switched to the standard xp10/8 combo and never looked back. I actually got all my passes in spec miata under braking. The xp10 is one of the best modulating pads I've ever ran. I also will be trying those cobalt xr2/3's that Bbundy runs for my next pads. I'll take those used pads off your hands though...pm me.

edit: I couldn't afford a "pro motor", or fresh 1/32 shaves every weekend, but I could afford the best brakes. Brakes are very important, no matter what pad you run make sure it performs.
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Old 05-12-2011, 02:35 PM   #19
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why does everyone still run a less agressive rear pad?
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Old 05-12-2011, 04:02 PM   #20
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I will be running blues on the back as well. Running aggressive rears only makes sense given the poor brake balance of the Mata.

I need to test the blues before I make any snap judgements. I can tell you that I did lock up the carbtechs a few times my first session back in the SM after many years out of the car, most likely due to using blues brake force on carbotech brakes.
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