travisnd

Rotor wear with XP20s
This is from Road Atlanta this past weekend (first time using 20s). These particular rotors have been on the car since comp school last October; always used 12s on them until now. They're DBA 2-piece in stock C5 size. The rotor surface is very grooved now.



Vs.


Rotor wear from XP12s
The rotors were on the car June 2010 through July 2011. Only ever used XP12s on them. Swapped to fresh rotors when I installed the Wilwoods for comp school in October 2011. These are now my backups. This is what I have always bee accustomed to with Carbotechs.


I knew 20s would be a little harder on rotors, but it seems that these are eating rotors like my old Wilwood H's. I.e. stop great, but chew through rotors quickly. This wear appear normal? Do they eat rotors that much faster, or do they just wear ridges into the ring vs. the smooth wear of the 12s?

For reference, the car is a 2001 Z06 racecar setup for NASA PTA/TTA. Weighs approx. 2850lbs and makes 365 rwhp. I loved the rotor/pad life I was getting with the 12s. I moved to 20s to combat what I thought was brake fade, but I now believe it was due to the limitations of the tiny 245 tires I'm running due to class rules. I don't want to be chewing through rotor rings every 2-3 weekends when I was getting an entire season out of them with 12s.



EDIT - Or did I screw up by slapping fresh 20s onto a rotor that had been always used with 12s and going out and racing? I didn't have time to scour the rotor surface or go bed-in the pads. I figured since they were both Carbotechs they'd be close enough to not have any issues???

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EDIT 2 Took the LF apart tonight to inspect...

LF rotor on the car


Lots of brake dust


XP20s and rotor on the left vs. XP12s and rotor on the right


Closer shot of XP20s and rotors



Closer shot of XP12s and rotors



XP20s


XP12s


My XP20s on the left vs. a used set I bought from a forum member. Mine are slightly more grooved.

jlutherva

Travis,
No answers, just questions.

In the first pic, is that a crack running the length of the grove? Sure looks like it. I don't recall seeing that kind of wear pattern on XP-12 or 16's.

In the second pic, I don't see the wear you are concerned about. Is it smooth and even and just presenting a ridge at the edge?

Any chance these photos are reversed?

I'm concerned about your statement of Wilwood H pads eating rotors. I just switched to these (C6Z Wilwood W6A calipers) but really have not pushed them very hard yet. I have noticed that pad wear is very good but did not notice rotor wear at all. I guess I know a lot more after NCM VIR.

Jim

travisnd

First picture - You're seeing pad material or rotor material built up in the rotor slot. No crack.

Second picture - This is the "good" picture. This is my spare rotors that have only had XP12s used on them. They're nice and smooth with a few heat checks (aka spider cracks) vs. the first picture where the rotor face is grooved pretty badly.

As for Wilwood Hs - I only ever ran them years ago with stock C5 calipers and stock NAPA rotors. They stopped great and didn't taper, but they were hard on rotors.

jlutherva

Dang, my reading comprehension continues to deteriorate! I've never run the 20's (KNS did not have them last year) but I did not see any of the grooving with the XP-16's.
Jim

travisnd

That's valuable feedback as the 16s are supposed to be the hardest on the rotors of all the compounds.

PushinTheLimit

Brian, I didn't really notice any difference in rotor wear with my XP12's, XP16's, XP20's. The 20's might've used up the rotors slightly more, but I felt it was worth it for the bite they had. But I was also running at CMP with those pads and that place just kills brake pads and rotors. I've never had any issues at places like Road Atlanta and VIR.

froggy47

If you run your fingernail across the rotor in the first pic, are those ridges, like the ridges on a Ruffles potato chip (not that DEEP but ridges)?

To me, that means either a) the pad material has some pretty hard bits that are blended into the compound, that are grooving the rotor

or b) the rotor is not hard enough to stand up to the pad.

Having said that, I have not used any of these, but to me that's what it looks like.

My rotors may heat check or occasionally crack, but they don't groove/ripple like that.

2 cents.

travisnd

They're ridges like a ruffles potato chip. I think it's from not bedding in the pad at all. I installed them and went and raced. I'm waiting to hear back from Carbotech, but I'm going to have this rotor turned, scuff-sand the pads, and then bed them in properly and see what happens at VIR next month.

The brakes just felt off all weekend. I couldn't engage ABS, I didn't get the smell normally created by hard braking, and the car just didn't stop as well as it normally does. When I swapped the 20s in I checked over everything and found nothing amiss:

* No bubbles in the fluid or signs of fluid degradation
* No pad taper causing a longer pedal
* No leaks etc.

Going to take it apart tonight and see if the pads are glazed. That'd explain the relatively poor braking, lack of smell, etc. but not sure why it'd make them chew up the rotors like this.

JVetthead

This is my 2nd season on xp20s, 2nd set of pads on last years napa rotors so I would say that is not normal.

travisnd

Thanks for the feedback

drivinhard

I love these highly technical threads

froggy47

JVetthead

I would talk to Carbotech tho and see what their thoughts are.

travisnd

I reformatted the OP in an attempt to make it more clear. The first picture is from the rotors currently on the car. The second picture is from a rotor that has only ever been used with XP12s and has nothing wrong with it. There is nothing wrong with my braking system other than the XP20s grooving the living heck out of the rotor vs. 12s which did nothing of the sort; as shown in the pictures.

froggy47

As far as cleaning the rotors and bedding in the 20's I would have done the same thing and assumed that pads from the same company that close to each other in performance would not require the procedure.

jaa1992

I've gone from panther (now autox pads) to xp8 to xp10 and now xp12 on the same rotors on my heavy 92 with no abnormal wear. However after 4 years these canada rotors are almost done

hope the OP gets it sorted out.

trapp

If you look at my thread you see my pics....the rotors have a few track events including Road of America.....they don't look anything like your Rotors....something wrong with the pad...
I used X16's on the same rotors this last weekend and they seem to wear the same except the stopping power was not as good...I prefer the x20's

Tomhttp://forums.corvetteforum.com/autocrossing-and-roadracing/3072968-are-these-rotors-still-good.html

travisnd

Carbotech has gotten in touch with me. Great customer service as always. Will update when I get to the bottom of this. All the compounds are supposed to be compatible so there should be no need to scuff the rotors swapping from 12s to 20s.

Z06Tracker

Brian, could your lack of stopping power have caused by skinny scrub tires. Kevin had the same thing on his driver side front rotor his weekend. have seen it twice on my car in the past

travisnd

That's what I thought. Even made a thread about it HERE, but most are saying I should have been into the ABS like crazy. However, no ABS all weekend, and no "hard braking" smell normally present.