Cracks in rotors
 

Ok, old, but still learning about cars and tracking..

After my last track night, looking at the rotors and I have noticed cracks in both front rotors. My assumption that they need to replace. They are Z1 Motorsport - Z1 (Sport) Performance Brake Rotors - Akebono. They have seen about 10 track events.

Also when putting on the brakes a lot of vibration, on most corners (street driving no vibration)

Not sure what is going on, looking to be educated on all of this...

(probably will reorder the Z1 (Sport) Performance Brake Rotors - Akebono, would look like the 2 piece rotors, but not time yet)

thanks for all the help/education/insight...
Cheers

Pictures?

Mirco surface cracking or cracks?

Cracks that extend to the edge of the rotor mean the rotors are toast.

Brake judder on the track and no judder on the road usually means you have hard spots on the rotor from heat soak at the end of a track session.

When a session ends, don;t park the car and leave it, you need to move the can forward 2 feet every minute or so such that no single spot on the rotor stays under the hot pads for more than a minute of so - which leads to differing hardness in the rotor

Also, what pads are you using on the track .... same as DD pads ?

And do you have any rotor cooling set up ?

Carbotech XP10 front/Carbontech XP 8 rear

yes I have stillen braking cooling in place

Thanks all for helping and the education

pictures:

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Your rotors are toast. You got cracks in the drilled holes. You should know better then to track with drilled rotors. :shakes head: They always start to crack at the holes.

Yeah, if you track, slotted only is the only way to go.

Be careful with the Z1 2-piece rotors. I know a few people who regretted their purchase when the rotors didn't stand up to their track abuse. Brake rotors act as a heat sink for cooling so more mass is not necessarily a bad thing. The unsprung weight reduction of the Z1 2-piece is really nice but the downside they run much hotter under extreme conditions.

You keeping an eye on DarkJak's rotor and caliper thread?

RacingBrake rings have some mass to them. They're thick.

Yeah you need new rotors unfortunately. If you only had short cracks at the drilled out parts I would say you are OK; But you would need to check them regularly to make sure they didn't grow into the long cracks that extend to the edge. Those mean the rotor can break apart at any moment under hard braking.

I have had a lot of luck with FrozenRotors, they are cryogenically treated rotors, they are relatively inexpensive and hold up to a lot of abuse. Simple blank rotors are what I use, sure they don't look fancy but they work well and don't break the bank.

There are many good rotors available. Two piece rotors are good bit they are very pricey and I don't feel the weight savings, increased performance, is there for the average user. For competition sure take every edge you can to win and have the sponsors share the cost or replacing them. Slotted rotors are good too but wear the pads down unnecessarily quickly for no real gain, unless your using pads from the 90s.

thanks all for the input and help, definitely teaching me a few things, and what to think about next year... Will probably redo the rotors totally based on the comments provided.

I order the same as before, Z1 (Sport) Performance Brake Rotors, with holes and slots, but was able to change my order just to slots. Doing another track event a week from Saturday, so figure ahead of time need to get them...

Thanks again
:tiphat:

isn't this exactly why cross-drilled is a poser mod?

less structural integrity due to how they're manufactured and less mass do soak heat, minimal advantage in airflow

two-piece for the weigh reduction and most versions have superior internal venting

or

upsize to bigger setup that has more mass (and other features)

What's funny. With cast iron. You drill holes at the end of the cracks to stop the cracks. Here, you already have the holes. And the crack starts at the holes. :icon14: Unequal thermal expansion and contraction of cast iron.

Good on you OP for keeping a close eye on your car.

(assuming this is a hobby and you aren't racing professionally) I don't think I can subscribe to moving my car every two minutes after pulling in to the pits.. I've been tracking my car for over fifteen years and have never done this. Yes, I'll get pad deposits caked on a section sometimes, and after my next session.. its gone. Do your best to cool the brakes on your cool down lap.. (stay off the brakes and roll at a good pace, not a crawl.) you'll be fine.

I avoid applying the E brake with my 7AT. Rear rotors get to 650F after cool down and the hat piece is right next to it, which is where the drum brakes are, too.
I have no idea how hot the stock drum pads can get before fusing but have always heard to not use the e-brake after getting off the track.

The 7AT has a parking pawl that locks so you get a transmission brake which has no chance of fusing due to heat.

That said, I don't move my car after it's parked either. Nor do I do it with my E36, which gets almost to just 100F less on rotor temps. While I worry a bit on uneven cooling due to the caliper trapping more heat, it hasn't been enough to crack a rotor.

Never apply the e-brake after coming off the track and parking. The e-brake shoes can stick the their drum.