Drilled vs Slotted?

[TheKosherStogie]

what are the different effects of each? what are pos/neg of each? Am looking at brembo bbk kit. What would you get?

[foosh]

Slotted is better.

In earlier days, cross-drilled was viewed as providing better cooling. Over time, experience has shown that heavily-used cross-drilled rotors can develop cracks emanating from the holes and propagating across the disk. You don't see many track cars with cross-drilled disks these days. They are more about "bling" now.

[bigjae1976]

Street and bling - drilled
Track - slotted

[aus]

To add to what foosh said, back in the old days, there was concern about pad's "gassing out" as they wore away, where gas would form between the pads and the disc, which could then separate the disc from the pads. The cross drilled rotors were suppose to allow a place for the gases to escape. Newer pads don't gas out anymore... at least that's what I've read.

[doba_s]

drilled rotors tend to crack if used a lot on the track ...

slotted is the way to go ...

[AMPowerJ]

I have always heard the same thing but does anyone actually know of someone that has had problems with drilled rotors? Here are some supercars that come with drilled rotors.

Corvette ZR1
Porsche Carerra GT and GT2
Lamborghini's
Ferrari's
Pagani Zonda
Audi R8

I am not sure if there are any that come with slotted rotors. So if all of these cars come with drilled how bad can they be?

[foosh]

Originally Posted by AMPowerJ

I have always heard the same thing but does anyone actually know of someone that has had problems with drilled rotors? Here are some supercars that come with drilled rotors.

Corvette ZR1
Porsche Carerra GT and GT2
Lamborghini's
Ferrari's
Pagani Zonda
Audi R8

I am not sure if there are any that come with slotted rotors. So if all of these cars come with drilled how bad can they be?

No one said they were even close to "bad" for street use, or even occasional track use. It was noted that a few years ago, cross-drilled used to be the technology of choice because it was believed that there were advantages in rotor cooling.

However, experience has shown that slotted is a better technology because of the cracking issues seen in cross-drilled rotors subjected to continuous very heavy use. It's not likely that even 1/10th of 1% of users of cross-drilled rotors will ever see a problem. They have now become the "bling choice," and the average buyer expects them in high-performance cars, so that's why you see them.

Nonetheless, if I were going to spend a ton of money on a BBK, like Brembo, I'd choose the slotted option, unless it were insanely more expensive, in which case I'd be fine with cross-drilled. That's all . . .

[dawgdog]

I chose slotted rotars because the reason I upgraded the brakes is that I frequently attend HPDE (track) events. My stock rotars are warped after about 10 track days.

[foosh]

In fairness, you'd have to compare slotted vs. cross-drilled of the same manufacturer, such as Brembo, as well as comparable size and spec. Your warped crossed-drilled OEM rotors weren't likely because of the cross-drilling, per se.

The cross-drilling issue is associated with rotor cracking, not warping, as I understand it.

[doba_s]

Originally Posted by AMPowerJ

I have always heard the same thing but does anyone actually know of someone that has had problems with drilled rotors? Here are some supercars that come with drilled rotors.

Corvette ZR1
Porsche Carerra GT and GT2
Lamborghini's
Ferrari's
Pagani Zonda
Audi R8

I am not sure if there are any that come with slotted rotors. So if all of these cars come with drilled how bad can they be?

Drilled look better, and how many people do you know who tracks their Lamborghini's, Ferrari's hard core ? I don't know many

Here is a real super car

[dawgdog]

Originally Posted by foosh

In fairness, you'd have to compare slotted vs. cross-drilled of the same manufacturer, such as Brembo, as well as comparable size and spec. Your warped crossed-drilled OEM rotors weren't likely because of the cross-drilling, per se.

The cross-drilling issue is associated with rotor cracking, not warping, as I understand it.

Agreed. Didn't mean to imply otherwise. I guess my OEM rotors held up pretty well considering how I abused them.

[powertrip]

I've seen NUMEROUS BBK kits with cracked cross-drilled rotors from too much track useage. With that said, these were Time Attack cars, not street driven cars tracked once or twice a month.

[808MGuy]

I had drilled rotors on my last car which I never tracked. It was a daily driver and towards the end of the rotor life, I did start to notice the hairline cracks around the holes. They were small enough not to be worried about them but I can imagine what they would have turned into had I tracked the car.

[AP Racing - Chris_B]

Originally Posted by sammyrusso

what are the different effects of each? what are pos/neg of each?

The reason why drilled rotors are used in events like Time Attack is that the provide a more aggressive pad bite when pushed hard. This is due to the extra leading edges from all those holes. I've seen plenty of IndyCar and Sports car teams use drilled rotors for qualifying and then move to slotted or J-hooks for the race, depending on driver preferences and team budget.

Drilled rotors will generally crack sooner when run at excessive temperatures (even sooner if they are low quality rotors or were drilled and finished poorly -- like stuff you see on eBay!). For 99% of people on the street, drilled rotors are not problematic. I would not recommend them for aggressive track use unless you have a nice budget for replacements or have a good sponsor! There have been actual studies to show what the pros and cons are, but I'll keep this post short for now.

Slotted discs provide slightly more bite than plain-faced rotors. The slots do a fairly nice job of keeping the pads clean and free from glazing. While doing that, they also cause a little bit more pad wear. It's hard to get something for nothing...

Short answer: If you are not going to track the car, either drilled or slotted (or both) is fine. For track use, go with slotted unless doing very short sessions (Time Attack) and like replacing rotors.

Chris

[swamp2]

Originally Posted by AP Racing - Chris_B

There have been actual studies to show what the pros and cons are, but I'll keep this post short for now.

This forum and many of its members like technical details. We would love to see anything you can share on this topic.

[isugoo]

German cars tend to come with Drilled and JDM cars come with slotted more.
So as the dumbest person like me, I like putting drilled on german cars and slotted on the jdm cars.

FYI, I don't track so pet boys replacement rotors will be fine for what I do. =)

[Subw00er]

Originally Posted by foosh

Slotted is better.

In earlier days, cross-drilled was viewed as providing better cooling. Over time, experience has shown that heavily-used cross-drilled rotors can develop cracks emanating from the holes and propagating across the disk. You don't see many track cars with cross-drilled disks these days. They are more about "bling" now.

+1

[AP Racing - Chris_B]

Originally Posted by swamp2

This forum and many of its members like technical details. We would love to see anything you can share on this topic.

I'm getting ready for SEMA right now, but a good place to start is SAE paper no. 2006-01-0691 published by a couple of GM scientists and professionally presented (i.e., not marketing blather on some company's web site). I'll post a few highlights in a summary later.

Chris