Pro's and Con's of drilled and slotted rotors

[Inodoro Pereyra]

Here is proof of why not to buy slotted and drilled. These are brembo brand. Now I stick to just slotted and dimpled on the front and blanks on the rear.

Is this your car?

No, that's just the brake rotor...

[mitmaks]

you know what I ment....

[Inodoro Pereyra]

I know. Just having fun...

[Ryan]

Looks like an MX-3 rotor to me...

[stereoking15]

Here is proof of why not to buy slotted and drilled. These are brembo brand. Now I stick to just slotted and dimpled on the front and blanks on the rear.

Is this your car?

Yeah this came off of my 94 GS this was a rear rotor, went to put my slicks for an autocross and saw this when I took off the wheel. Mooneggs and I searched all of Eugene, OR to find a set. 6 parts stores later found a set at Autozone and installed them before the race! FTW

[Inodoro Pereyra]

Your REAR rotor???
You mean your rear rotor cracked like that, and (I assume) your front ones are ok?
Something is very wrong with that picture...

[stereoking15]

That is the pic we took after I discovered it was cracked. Needless to say I actually used to trailer it around so had no real way of knowing it was bad until I went to put my slicks on. Yeah I changed my front rotors out when I noticed some spider cracking around the holes. This is the actual rotor off my car!! Ask Mooneggs he was there. Nothing like doing repairs at a race.

[stereoking15]

Here is another pic so that you know i'm not kidding on this one.

[Mooneggs]

Yeah I was there and drove him around to find a replacement still wondering what caused it to crack like that though...

[Ryan]

I told you before, but you all call BS on it

STRESS CONCENTRATIONS!

Putting a hole in a something creates a stress concentration around the hole. The rotor was designed to handle a certain allowable maximum stress, given a certain quality control for the largest crack in the material (small small scale). The hole is clearly larger.

[wytbishop]

Here is proof of why not to buy slotted and drilled. These are brembo brand. Now I stick to just slotted and dimpled on the front and blanks on the rear.

Ok I'm going to split a hair here, but this is not PROOF that drilled and slotted rotors should not be used. It is definitely evidence that these particular slotted and drilled rotors (this brand, maybe just this batch) were not up to the application you used them in; i.e. track day, but there are many reasons why this might have happened. Could be the machinist that did the work had a bad day or the machine had a dull cutting tool, could be that they're not really Brembo (I'm sure they are I'm just sayin'), could be that the abuse of a track day was too much for them and this would happen again if you replaced them with the same part, but another brand might be fine.

I'm simply saying that one example of broken rotors in a particular situation doesn't constitute definitive, imperical proof that slotted and drilled rotors are a bad idea.

[stereoking15]

Here is proof of why not to buy slotted and drilled. These are brembo brand. Now I stick to just slotted and dimpled on the front and blanks on the rear.

Ok I'm going to split a hair here, but this is not PROOF that drilled and slotted rotors should not be used. It is definitely evidence that these particular slotted and drilled rotors (this brand, maybe just this batch) were not up to the application you used them in; i.e. track day, but there are many reasons why this might have happened. Could be the machinist that did the work had a bad day or the machine had a dull cutting tool, could be that they're not really Brembo (I'm sure they are I'm just sayin'), could be that the abuse of a track day was too much for them and this would happen again if you replaced them with the same part, but another brand might be fine.

I'm simply saying that one example of broken rotors in a particular situation doesn't constitute definitive, imperical proof that slotted and drilled rotors are a bad idea.

I agree with you to a point as well. Most of the Ferrari, Maserati, and Lotus cars we get have drilled, slotted, or both but the materials themselves are much higher in quality then this Brembo piece. Since the holes are often times cast into the rotor making it stronger versus being a just a drilled piece which causes them to be weaker. A lot of the rotors on the higher end cars are carbon which is the best in the world but do not have quite the same failure as metal. My recommendation is not to use drilled in a racing application, even low speed such as autocross. Slotted allows you to use more surface area and is not detremental to the structure like drilling is.

[Inodoro Pereyra]

Yeah I was there and drove him around to find a replacement still wondering what caused it to crack like that though...

I wasn't doubting Stereoking's word. At this point, all I can think is that the blank they used for that rotor was bad (probably a casting mistake, or impurities in the metal). Otherwise, it makes no sense at all that the rear rotor would crack like that, and the front rotors (that take most of the stress of braking) would survive.

Stereoking: it's not that using cross drilled rotors is bad, or that carbon rotors are stronger. If you go read on Porsche's forums, for example, you will see carbon rotors actually crack faster than metallic ones. The advantage of carbon rotors is that they're much lighter, which makes a big difference in racing, when it comes to handling.
Cross drilled rotors aren't better, nor worse, than any other type of rotor: they're just meant for a very specific application, and come, like everything else, with their own set of pros and cons. If you use them for properly (for serious racing, when carbon rotors are not allowed), they are unbeatable (because maintenance costs are not a concern, and cars are completely overhauled after almost every race), but, if you expect them to have the durability of OEM rotors, you will be sorely disappointed.

[stereoking15]

Yeah I was there and drove him around to find a replacement still wondering what caused it to crack like that though...

I wasn't doubting Stereoking's word. At this point, all I can think is that the blank they used for that rotor was bad (probably a casting mistake, or impurities in the metal). Otherwise, it makes no sense at all that the rear rotor would crack like that, and the front rotors (that take most of the stress of braking) would survive.

Stereoking: it's not that using cross drilled rotors is bad, or that carbon rotors are stronger. If you go read on Porsche's forums, for example, you will see carbon rotors actually crack faster than metallic ones. The advantage of carbon rotors is that they're much lighter, which makes a big difference in racing, when it comes to handling.
Cross drilled rotors aren't better, nor worse, than any other type of rotor: they're just meant for a very specific application, and come, like everything else, with their own set of pros and cons. If you use them for properly (for serious racing, when carbon rotors are not allowed), they are unbeatable (because maintenance costs are not a concern, and cars are completely overhauled after almost every race), but, if you expect them to have the durability of OEM rotors, you will be sorely disappointed.

One of the main proponents of why they went to carbon rotors is heat, the carbon rotors can handle and dissipate the heat much faster then the steel ones and are less prone to heat soak fading therfore more stable, and for the most part fade free. The pads themselves for the carbon rotors wear out but at our dealership we have actually never replaced a carbon rotor. They just dont wear out but when they do are like 2-4k for just 1 carbon rotor

[Ryan]

I agree this isn't proof that all drilled rotors are s---... but it adds to the statistics.


Inodoro, the front and rear rotors are totally different designs. You can't say which would break faster. The liklihood of a material flaw in these is just the same as a blank rotor. Hopefully less in the drilled rotor, if quality control is of any concern, since they'll be accounting for the holes.

Isn't it interesting that the crack passes RIGHT through the outer hole....

I'm actually taking a class on materials as we speak Doesn't make me an expert by any means, but I have insight .

I still vote against cheap drilled rotors. Also, I have this sneaking suspicion that Brembo is riding along on their reputation from brilliant marketing, not their quality.