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Discussion Starter · #1 · (Edited)
Hey Fellas,

Has anyone ever cracked their rotor? I attended my second trackday yesterday and thought I quit while I was ahead. I only did 3 of the 5 track sessions because it was extremly HOT at Thunderhill in Willows California.

This was my second trackday on my car, 2002 Z06. The first trackday I experinced brake fade after my first session out. So, to fix that problem I put in new brake fluid. ATE super blue and also put on goodrich SS lines because I was under the car anyways. Upgrades to make the car feel and brake better are worth it to me.

However this trackday I was eager to see how much improved my brake feel was and to not get any brake fade (mushy pedal). Everything was going great, brakes felt good etc. etc. Never had any problems while on the track with my brakes. Felt good. When I was leaving the track, that's when I noticed a puslating feeling in my pedal. I was like, "Oh crap, what did I do now?" talked to my friend who was in another car behind me and from what I told him, he thought I warped my rotors. So we're going to the gas station, pull in, get out, and look....... WOW :jawdrop:, thats a BIG crack through the rotor all the way up. None of my friends had ever seen anything like this before. Ya, the rotors were blue, and they were earlier in the day when I looked at them. Now there were at least 5 heat cracks within the contact space with the pads, and a big one going all the way up!

So, my question is, has this ever happened to anyone else with a vette, not race car of course, with 2 trackdays? I honestly dont think I was braking late or deep at all. Any opinions on what I should do? I'm sure this wont be covered under warranty :lol: :lol: :lol: So what kind of rotors should I replace them with? Baer? Any other damage that I cant see that I might look for??

Thanks for helping a noob,

Steve

:z:
 

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My rotors last about 3 two-day track events, before I start seeing the "spider" cracks in the front rotors(the rears will last a LONG time).

then I swap them out, so I have never had this problem.

I am wondering if the rotors are original from the factory? If so, and you bought the '02 new, that's about 3 years of normal driving, plus track time. Lot's of heat/cool cycles not to mention temperature variances..

A lot of the DE folks and racers here, including me, use the Raybestos(or NAPA, same thing) rotors. They are as good/better than original, are very high quality(I know i have NEVER received an imperfect one), and are cheap. I get mine from www.rockauto.com for $18.50 each.

Baer makes a great rotor, but if it was me, I wouldn't waste a good rotor like that if I was still using the stock calipers/pads-just my opinion. Plus, I would be interested in how long Baer's last under DE conditions-not sure, but I would hope a long time! :cool:

I know that Leslie(BLKZ06) cracked a rotor at a DE event, so it does happen from time to time.

You might want to put a light on the rotor to see it reall good, and check for the spider cracks I mentioned. Lot's of squiggly lines running from the inside to outside of the rotor. If you see them reach to about 1 inch of the outside edge of the rotor, then yes, I can see why it might have cracked...

Finally, DJ Worm has some excellent posts regarding brakes and how to get set up for a DE event. next event, you might consider not only putting in DOT4 fluid like you did with the super blue, but ALSO bleed them before putting in the new fluid to get the old stuff with moisture and air out of the system.....
 

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I have heat cracked 2 sets of rotors on the street. So cracking at DE's should be a routine affair. ;)
 

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The front rotors and pads on my '02 were replaced under factory warranty when they cracked the first day I used it on a roadrace track. It didn't take long to discover Active Handling was causing the problem. I turn A/H and Traction Control off now. With it all off the lap times are much better and the rotors last several days before getting the "micro cracks" instead of large cracks in two hours of track time. A cool down lap with no brake usage really helps keep the rotors in good shape. Letting them cool too fast by getting water on them while hot will also cause them to crack.
 

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Expect rotors to be a replacement item when you change pads. They crack way to easy especially if you don't bed them properly.
 

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Discussion Starter · #6 ·
jnjboc said:
My rotors last about 3 two-day track events, before I start seeing the "spider" cracks in the front rotors(the rears will last a LONG time).

then I swap them out, so I have never had this problem.

I am wondering if the rotors are original from the factory? If so, and you bought the '02 new, that's about 3 years of normal driving, plus track time. Lot's of heat/cool cycles not to mention temperature variances..

A lot of the DE folks and racers here, including me, use the Raybestos(or NAPA, same thing) rotors. They are as good/better than original, are very high quality(I know i have NEVER received an imperfect one), and are cheap. I get mine from www.rockauto.com for $18.50 each.

Baer makes a great rotor, but if it was me, I wouldn't waste a good rotor like that if I was still using the stock calipers/pads-just my opinion. Plus, I would be interested in how long Baer's last under DE conditions-not sure, but I would hope a long time! :cool:

I know that Leslie(BLKZ06) cracked a rotor at a DE event, so it does happen from time to time.

You might want to put a light on the rotor to see it reall good, and check for the spider cracks I mentioned. Lot's of squiggly lines running from the inside to outside of the rotor. If you see them reach to about 1 inch of the outside edge of the rotor, then yes, I can see why it might have cracked...

Finally, DJ Worm has some excellent posts regarding brakes and how to get set up for a DE event. next event, you might consider not only putting in DOT4 fluid like you did with the super blue, but ALSO bleed them before putting in the new fluid to get the old stuff with moisture and air out of the system.....

Do you happen to know the part number for these rotors?? Im looking at Kragens since we dont have a rockauto here. http://www.partsamerica.com/ProductList.aspx?parttype=221&mfrcode=RAY&ptset=A#
 

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jnjboc said:
Finally, DJ Worm has some excellent posts regarding brakes and how to get set up for a DE event. next event, you might consider not only putting in DOT4 fluid like you did with the super blue, but ALSO bleed them before putting in the new fluid to get the old stuff with moisture and air out of the system.....
Yep, cracking rotors are t be expected. In addition to above, do a search on DRM ducts and read about how to add better cooling to brakes. It does work.

As others have said, these rotors are cheap and should be just considered disposable parts - just replace them on a regular basis. When I go to the track, one of the group always brings an extra set just in case one of us needs them.


On the last point of bleeding the brakes, you basically can't do this enough. I would recommend that you do it before every event., new fresh fluid with no air in the lines is your best friend on the track. Good Luck :thumb:
 

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Although the Z06 can be tracked right off the showroom floor the weakest link is the OEM rotors. They are made in Brazil and have poor metallurgy. When these are tracked they will warp and crack very easily.

You have three options:
1. Consider the rotors disposable and swap them every or every other event.
2. Prepare the OEM units or better OEM replacement rotors
3. Install better quality racing type rotors.

Avoid drilled rotors as it only exacerbates the problem.

The heat checking and cracking of rotors is caused by excessive heat, induced thermal stress, induced mechanical stress. cracks start microscopically and most begin on the inside of the rotor vanes where there a many stress risers.

At the very minimum I recommend
- having the rotors cryogenically treated with a 3 step and final heat treat process similar to Diversified Cryogenincs processses. (reduces or relieves mechanical induced stress)
- installing DR's Front Cooling duct extensions and either LG Motorsports or Phoenix spindle ducts.

These 2 steps will increase the rotor life 3-4 times which is cost effective and saves time in always changing rotors as would be the case in the first option.

You can also use some advanced techniques on cars that see greater track time:
- extrude hone the interior vane surfaces to reduce or eliminate the stress risers and improve vane air flow & cooling.
- Sub harmonic treat the rotors to relieve the induced thermal stresses
- Coat the internal vane surface with a temperature release coating
- Install a water injection mister to reduce the inlet duct air temp

If your rotors are blued they have been over heated, over used and under cooled. Microscopic cracks have already started.
 

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It's fairly common.

Do a search on Subdriver & rotors. He had some nice pictures.

With my last set (Raybestos), I have made a conscious effort to warm them up over at least one lap of easy/minimal braking and again let them cool off for at least 3-5 minutes before getting off the track. They have some heat checks on the surface, but no cracks so far. I think they have about 5 hours of track time on them so far.

I always carry spares.
 

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DJWorm

The problem with doing what you are suggesting is that although you may get twice the life out of a set of rotors, you are talking about at least 4 times the cost. Considering that most of the DE guys like myself get plenty of practice doing brake work, changing out the rotors is no big deal to us, so why pay extra when it's not needed.

I tried to get the expensive rotors that promised longer life, thinking that it would be worth paying extra if they performed as advertised, and believe it or not, they did last any longer. For the price, I could have purchased 5 sets of rotors and could still be burning through those.
 

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Lancer,

If you look at the first part of my suggestions it ONLY suggests Cryogenically treating a new set of rotors and adding cooling ducts.

You should add the cooling ducts no matter which rotor or option you choose. I get a set of rotors treated for $50 so that is only 1/2 the cost of a set of the cheapest rotors.

I also stated that the Cryo'd rotors will last 3-4 TIMES LONGER than a set of cheap rotors NOT ONLY 2 TIMES LONGER as you said I said. So do not mince my words or minimize my recomendations.

Let's look at the numbers:
Let's assume that the rotors are new so that cost is $0 (new OEMs on a new car)
Let's assume you can't get racers support and pay $30 per rotor for Cryo.
Let's also assume that the fronts wear, crack & warp more often than the rears on a 3:1 ratio
Let's also assume that you have to ship the rotors for Cryo but you can get the cheap rotors at your local NAPA store

$120 = Cryo'd process
$ 30 = Shipping
$150 = Total Cost of Cryo'd rotors

$ 52 = 1st set of cheap replacement rotors @$26/rotor (fronts only)
$ 52 = 2nd set of cheap replacement rotors (fronts only)
$104 = 3rd set of replacement rotors (fronts+ rears)
$ 80 = Labor replacement cost (real or personal) (2x$40)
$288 = Total Cost of cheap replacement rotors

It's not that I abhore changing rotors, only that my time is better spent doing more important things. My hourly rate is also much higher than $40/hour.

It could be that you did get less than 3 times the wear and you will by
- not bedding the rotors in
- not bedding the pads in
- using a high wear racing pad rather than a carbon/carbon or carbon/kevlar racing pad
- not running brake duct extensions
- not running spindle ducts
- not warming the brakes up
- not cooling the brakes down
- washing the wheels with hot brakes
So my statement that the Cryo'd rotors will get 3-4 times the life of non-cryo'd cheap rotors is really an understatement for a dual use, occasionally tracked car. It is fairly accurate say for a dedicated T1 car

In fact I track my car in high speed Solo I Time Trial type events at least once a month, and also participate in National Tour and Pro Solo events 2 times a month for the past 5 yearsand it is a daily driver in the summer with 27,000 total miles. I take October, November & December off so that is 27 events per year or a total of 135 events.
I have a back up set of Cryo'd rotors which I rotate every year. I have NOT replaced 1 set of rotors so each of my sets have at least 62 events on them.

Of course my rotors have had ALL of my suggestions done to them; including extrude hone and coating. My rotors have lasted 31 TIMES LONGER than a set of the cheap crap !!!!

That's a savings of $2,880 and my car stops like a big brake car !!
(31/3 = 10 x $288)

There is NO comparison. Using cheap rotors and replacing them every other event is a short-sighted alternative.
 

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Though I don't compare to DJs experience, looking after rotors (warm up, cool down, treatments, etc) have let me run the same pair of good quality rotor sets for dozens of track events in Australia. My first OEM rotors became so badly hot spotted after 1 track day I took them off and threw them away.

My point is that buying good quality rotors and treating them well will likely work well. YMMV

My point is that buying cheap rotors or treating them badly will likely work poorly. YMMV

This point of view (buying good quality rotors) seems unpopular based upon the number of thread discussions, but I would really rather not have rotors cracking.

Rotors cracking (at any time let alone at speed) cannot be anything other than dangerous.
 

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One other factor that can quickly crack rotors is leaving the active handling on. Especially if you have relatively fast, off camber turns which really upset active handling. I once cracked a rear in a single session at Laguna when I forgot.
 

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DJWorm said:
In fact I track my car in high speed Solo I Time Trial type events at least once a month, and also participate in National Tour and Pro Solo events 2 times a month for the past 5 yearsand it is a daily driver in the summer with 27,000 total miles. I take October, November & December off so that is 27 events per year or a total of 135 events.
I have a back up set of Cryo'd rotors which I rotate every year. I have NOT replaced 1 set of rotors so each of my sets have at least 62 events on them.
DJ, When you do these events, is it like a DE? I mean are you driving 4 hours on the track for the w/e or is it just some practice then the time trail?

I could be wrong but are these auctcross events that you are doing?

http://www.na-motorsports.com/Organizations/SCCA/Solo/#Pro_Solo

thanks! :thumb:
 

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1 big crack on the frt rt rotor all the way through

My wife & I run in NCCC Hi-Speed time trials. This year I bought new factory rotors and Hawk HT-8 pads for running at the track. We put 200 laps on the rotors between April & July. I started seeing micro-fractures after 20 - 40 laps. We usually make 4-5 practice laps each and take a break, then do the race, which is 2 laps per event and 4 events per day. Since we are a 2 driver car, there are times when I run 2 hot laps, then my wife takes the car and does 2 more hot laps. Then we get a 20 min break while another group runs, then we repeat the process until 16 laps total are made. The rotors get really hot. After our 200th lap of the season, I heard a "thump-thump" noise just like you described coming from the front right wheel. Upon checking, we found the rotor had a crack from the bottom of the "groove" all the way to the outside, and completely through the rotor! This is the first time this has happened to us, but other club racers with much more track time have had rotors crack also. I am going to take DJWORM's advice and get some Frozen rotors, because I don't want to spend my off track time changing rotors! My wife & I are not blazing fast, nor are we that hard on brake pads. After 200 laps the HT-8's still have 75% of the pad left. We typcially race with "Competitive handling" turned on. I just wanted to add weight to the point that the stock rotors seem to get micro fractures and cracks too quickly and everyone should check the rotors carefully and carry spares if you race alot.
 
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