Rotors.. Slotted Vs Cross Drilled *Updated Pics*

[WhiteGTB]

Before posting this topic I did ALOT of reading... type in Slotted Vs Cross Drilled in Google and ALOT of responses came up. Forums, reviews, articles and general bits here and there.

So many debates, back and fourth. Pros and Cons. Percentages (although I am abit dubious about percentages, cause 40% of statics are made up on the spot... or was it 48%).

This ain't another debate, I can read all those on the net. However..

1. Wondering if anyone has used one or the other and had some personal experiences with them?

And

2. If anyone has used both and have found crackings on either one?

Thanks in advance

[coyote]

I've cracked cross drilled, slotted and plain rotors.

The only ones I'd say were caused by anything other than abuse or stupidity (and various combinations of both) were the crossed drilled. I had two sets crack badly for no good reason.

You can crack any rotor if you try hard enough or are dumb enough though.

Porsche seem to make cross drilled rotors that don't crack for no reason, but I believe they are cast under low pressure with the holes in the casting, rather than drilled (or something like that).

That's expensive and from what I understand, the shape of the ventilation vanes and angle of slots makes more difference to heat and gas/dust dissipation anyway.

I run my car on 10% ethanol, but I wouldn't mess with cross drilled rotors unless they were $10,000 a piece gold plated ceramic jobbies with carbon fibre vanes and built in microprocessors *.

* Slight exaggerations may appear in this post

[tangcla]

How do you intend on using them? I've heard reports of crossdrilled cracking, but then again, I'm sure if you slammed on the brakes hard enough you could crack anything.

I'm using slotteds at the moment (DBA5000 front, DBA Gold slotted rear) with no problems.

[swingn]

I heard a lot of bad reports for people who have put cross drill rotors on their car as an upgrade (Discs cracking).

As Tangcla suggested, I'm also unsure under what conditions these are under. From my understand (Could be very very very wrong here) but when you have say a conventional disc or a slotted disc, if you get them really hot & then just stop, you can warp the discs - Thus why at track days you'll generally have a "cool down lap" - But with with drilled rotors they may warp or worse, crack... Anyway, thats what I've heard.

I've also noticed that companies like DBA rate their slotted rotors as "club racing" brake, where as the cross drill in the same range generally are only rated for "general use".

Just to confuse the issue, my old man's 911 runs slotted rotters front & back & he's warped them before on the track, but he has never had a cracking problem... Porsche brakes are manufactured by Brembo by the way

[WhiteGTB]

Thanks for the information Coyote.

Do you track your car much? Would that be the reason for the cracking?

[coyote]

Do you track your car much? Would that be the reason for the cracking?

Not the Liberty, the cracked rotors were on wrxs.

The biggest reason was not warming up and cooling down properly.

[Roddez]

Let me start by saying that I am really dredging up stuff from a long time ago, so I could be very wrong, but....

I think that all brakes are cast with their final finish, be that slots, or holes. The main reason is that when you work metal, you change its properties. For instance, if you were to drill holes into a rotor, you would locally work harden the metal around the hole. Depending on the temperature you achieved, you will change the structure and hardness of the metal. This could lead to cracking or vastly different wear patterns in the metal.

Heat treating metal after it has been cast can change the characteristics of the metal as well, and in some cases can almost reset the crystalline structure. Just do a Google search on heat treating.....

And yes, when you hammer your brakes, you are heat treating them.

Another issue is quenching metal - rapid cooling. This also changes the properties of the metal. It can make the metal more brittle and it can also cause it to change shape because it doesn't cool evenly. Uneven cooling, not necessarily by quenching, can also introduce localised stresses into the metal which can lead to cracks and ultimately failure of the part.

I think I recall being told that cross driller rotors would help do dissipate the buildup of water between the disc and the pad. But I would imagine that slots would achieve the same thing. It's interesting to note which cars have slotted and cross-drilled rotors as standard. Also, have a look at the V8's. A few years ago, they were all cross-drilled, now they all appear to be running slotted.

Personally, I think that the cross-drilled look better, especially under calipers that bear a brand name such as Porsche, Lamborghini or Ferrari...

[ultrablue]

i had harrop drilled rotors on my clubsport r8 had no cracking

[Arith]

I used to have cross drilled on my Honda Legend a while back. Didn't have a single issue with them. Of course I never tracked the car. But I think if you don't track or occasionally track the car, it should be okay for cross drilled if you're so inclined.

[jdm rsk]

i have had cracks in cross drilled rotors..

[smythie]

Also, have a look at the V8's. A few years ago, they were all cross-drilled, now they all appear to be running slotted.

The V8's have been running a control brake disc/caliper package for the last couple of years in an effort to curb development expenditure on brakes. (I have Alcan on the brain, something like that anyway) The control setup is (as far as racing goes) just adequate and certainly not as good as some of the exotic stuff some teams were running. Guys have had issues with over or under cooling the brakes and it took till at least midway through this year before most had their heads around what they needed to do to get the best out of them

[WhiteGTB]

Had a chance to discuss this with Tony Dunn from VSport, he is the importer of Brembo's by the way and anyone that orders new Brembo's in Australia go through him. He also does some racing himself, so I am guessing this guys knows his stuff.

Slotted Vs Drilled.

He asked me a few questions on my intended use of the brake upgrade first up. Track days, how many? Once a week? Once a fortnight? Monthly? Quarterly? If yes to any of these, then no doubt slotted.
If general road going use, spirited driving and the occasional 1-2 track days a year then the drilled will suffice. He also mentioned the quality of the rotors play a big part.

Anyways, just another post for ppl to read if interested.

[senator]

trieu

mate I have seen braking systems for high speed trains, which a no different to car, forget drilled, slotted is the go.

i agree with the quality of the rotor, but also pads play a big role in it too, before the dollar went south, i was going to get the dixcel rotors and type m pads, they were slotted, and the specs of rotor compound and pads were will suited to both hard driving and track use. they both covered a large temperature range, which is what you need to look for.

don't for get your brake lines too....

bendix will be releasing ceramic compound pads........ little dust and lots of bit, should be on the market q3 2009....... if you can hold out that long

[Arith]

You're too late, Tony ...

[WhiteGTB]

Guys, thanks for your help but it seems like I am swimming against the tide for this one...

Before I get flamed Just wanna say that I had a choice at the time, slotted or drilled. I ended up with the drilled.

The moment I see a hairline crack, the slotted rotors are going on and at the price of about $700 for a set of Brembo's slotted, I can live with that.

These are so much better then the stock brakes.... so so much better