DO NOT take cheap cross drilled rotors to the track!!

[markstoys]

Everyone should already know it, but...

This happened at my last driving event at the Streets of Willow, on Aug. 16. I got these rotors off ebay years ago, and they lasted almost 5000 street miles and a couple of previous driving events with no issues.

I was driving REALLY hard this time, and they got REALLY hot. Oddly, the other rotor didn't crack at all. This one has four major cracks and several small ones on the outside, but only ONE on the inside I think it was because this one was on the upwind side of the car as I had it parked in the pits.










And these were crack free before the event--I check them all the time. Anyway, cross drilled is probably OK for the street, but not for the track.

Mark

 

[Spinnetti]

lol.. that's drilled rotors for you. You don't need drilled or slotted; that's mostly for show (slotted better as there's less stress concentration). The rears are thin too, so crack more easily. I put on some serious race miles and don't have any problem with the fronts; just run plain ones in the rear, and get better brake pads.

 

[4U2QUIK]

this is why I only run brand name rotors.

 

[Spinnetti]

Brand name aren't any better. Don't use thin, drilled rotors is the lesson. Slotting is ok. Neither is needed with proper brake pads, but look cooler. Brake pads matter MUCH more than any rotor. I've put three 24hr enduro races on a pair of rotors I paid $7 Shipped! (and have had toyota rotors fail right off) its a crap shoot either way...

 

[markstoys]

Brand name aren't any better. Don't use thin, drilled rotors is the lesson. Slotting is ok. Neither is needed with proper brake pads, but look cooler. Brake pads matter MUCH more than any rotor. I've put three 24hr enduro races on a pair of rotors I paid $7 Shipped! (and have had toyota rotors fail right off) its a crap shoot either way...

This is exactly what I have heard.

When I was first putting the car together, I just wanted some cheap rotors--and found that cross drilled and slotted ones weren't much more than plain ones, plus they look cooler. No more drilled or slotted for me.

When I saw how cracked the rotor was, the first thing I thought of was my pads, because I have Porterfield R4's and just the rear pads cost more than all four of my Ebay rotors. Luckily the pads did not get chewed up.

 

[rdm20fan]

Mark, thats a rear rotor isn't it? I wouldn't have thought the stress on the rears whould be enough to do that.

I do have drilled Ebay rotors on my front, and in the 1/4 I'm running 132MPH. i have noticed small cracks froom the holes simular to your lower photos.

I'm really suprised about the rears cracking.

 

[stevechumo]

I don't track my car, so I can't say for sure if the pad material has anything to do to heat up and crack up the rotors or not. However, I use drilled/slotted R1 rotors (cheap) with ceramic pads and they're fine for streets. Maybe if semi-metallic pads are used, they gets hotter than ceramic pads, and that crack the rotors.

 

[markstoys]

Mark, thats a rear rotor isn't it? I wouldn't have thought the stress on the rears whould be enough to do that.

I do have drilled Ebay rotors on my front, and in the 1/4 I'm running 132MPH. i have noticed small cracks froom the holes simular to your lower photos.

I'm really suprised about the rears cracking.

Yes, it is a rear. I have adjustable brake bias, and it was set with WAY too much rear bias. How hard are you on the brakes after a run? Because unless you are at the limit of traction EVERY time, and have wide sticky tires up front--then I wouldn't worry.

I don't track my car, so I can't say for sure if the pad material has anything to do to heat up and crack up the rotors or not. However, I use drilled/slotted R1 rotors (cheap) with ceramic pads and they're fine for streets. Maybe if semi-metallic pads are used, they gets hotter than ceramic pads, and that crack the rotors.

It probably does, because my first track event (at California Speedway: 130mph-0 and 110mph-0, every lap) was run with Autozone pads that faded like crazy after the first stop--no cracks. Second event was at Streets of Willow (110mph-0 and 100-0, each lap but with Porterfield R4S pads--still no cracks. Last event was also Streets of Willow, but with R4 (full race) pads--and that's when they finally cracked. I wasn

I think that better pads put more heat into the rotor before fading and losing friction, so rotors are more likely to crack

 

[samsdad]

Just a point to note as I'm in the brake game now after taking over a workshop 5 months ago... 99% of disc rotors are now from China. Spend the money and buy "name brand" so you have recourse on the supplier should the product not stand upto its intended use. This means you need to go to the supplier and tell them what you want and what you are going to use it for. Measure the original thickness of the rotor and take note of the minimum thickness. Do not have any machining done to within 0.5mm of the minimum thickness. Oh and cross drilled rotors do tend to develop cracks around where they are drilled whether road driven or comp

 

[4U2QUIK]

I drift and drag race my lsx Cressida. I've ran cross drilled brembos (Italian made) with ebc red brake pads for the last year at every event and daily driving. No cracks whatsoever. When I got them new you could immediately tell the difference from other rotors. Better material, better machine work, better quakity casting, and much beefier than any others I have seen.

 

[hiluxfan]

With a cross drilled disc under full race conditions this will happen sooner or later. I have even had AP and Alcon discs crack like that. There is also no supplier that will give you a "guarantee" on any parts used in racing.