Mighty Shilling

I'm needing rotors soon, so what's the general consensus on cross-drilled rotors?

I've heard the bad (they can crack) and I've heard the good (they do help with cooling and reducing brake fade)

but how many people here run them? any problems with em?

NZ951

I ran them for a year, Zimmerman brand. No issues. They come stock on many new performance cars, thats enough proof for me that they are ok to run.

tommo951

It all depends on how they are drilled and with what and of course what the rotor is made of.

There are drilled rotors/discs and drilled rotors/discs. I am getting some AP Racing supplied discs for mine. Its one area I would not cut corners. Always check the manufacturer is well known and has proper product liability rather than some supplier who buys cheap rotors drills them themselves and then sells them on ebay. Zimmerman are a reputable brand

Mighty Shilling

I was looking at the ones from Paragon... it's been my experience that Paragon sells a quality product. looking at em again, the rotors Paragon sells are zimmermann, and I know they have a stellar reputation in regards to quality.

tommo951

Paragon only sell reputable stuff in my experience

SD Porsche Fan

Probably more bling than performance. I heard that slotted are actually better.

Mighty Shilling

I heart Paragon

tommo951

Shouldn't believe everything you hear then!
On a solid disk/rotor slotted are better as they dissipate heat and gas. On a vented turreted disc/rotor a well designed drilled disc/rotor will dissipate heat and gas better than a slotted disc/rotor

SD Porsche Fan

Oh, I dunno. Now I've just heard that slotted are better on solid rotors and cross drilled on a vented.

blodstrupmoen

waste of money , less mass to absorb heat and to create friction between pad and disc.
THEY WILL CRACK either they are borred after or cast with holes .. Later is nevertheless regarded as the best , even though none is truly casted.
They are forbidden on some(most) race tracks , because they will crack.
If you have issues with youre brakes beeing to hot , then you ought to take a look at the air supply . ( I.e when lowering a 944t , the cooling ducts HAS to be alterd otherwise the airstream will not hit correct on the cooling sheild)

It is said that they will perform better than non drilled disc in rain ..
*And not atleast you get several hundreds street cred points for using them

All in all I can see no reason to spend the extra cash for a set of drilled rotors.
If you really are serious about brakes , then maybe a set of PFB floating rotors would be the way to go ..


Do some reading on the tech articles on wilwood and other serious brake manufacturers web sites

sawood12

I've had Zimmerman x-drilled on mine before my Big Black conversion and they seemed to stand up OK with no cracking issues - but then again I'm not the hardest-core trackday guy around so I wouldn't expect to be working them as hard as people who track their car more and track them harder. They were noisy at slowish speeds - a graunching noise as I decelerated through 40 to 30mph. Not a problem really, I quite liked it. I didn't bother when I installed the BB's and went for the standard 964 non-drilled disk and I certainly have had no problems in the braking dept.

The experience of the GT3 chaps here in the UK who do track their cars frequently and hard is that they are more trouble than they are worth and are ditching them in favour of non-slotted/drilled disks. The problem is chronic cracking no matter how carefully you warm up and cool down the brakes - it seems to be unavoidable no matter what brand. The holes also block up with brake dust that bakes itself in there and is very difficult to remove as it goes rock-hard- therefore over time you end up with the majority of your holes blocked so what's the point? They seem to be going for 2-piece after market non-drilled or slotted rotors - PF ones seem to be pretty popular.

Certainly for the street the will offer no advantage whatsoever apart from aesthetics.

I'm not convinced about any advantage they will provide in the wet either. Since the disks are positioned inside the wheel, will be pretty hot and spinning pretty fast any water that splashes on the disk surfaces will be thrown off pretty quickly. And any moisture that finds it's way between the tiny, almost non-existent gap between the pad and disk will be squeezed out pretty quickly.

I've read that the only reason Porsche introduced them in racing in the first place was for weight saving rather than braking performance improvement but they did find some performance advantage so continued to use them.

Red1

That's what people say. My question is, when? I've run Zimmermans for four years, and they have not cracked. I've run on tracks with C5 corvettes that've cracked their OEM rotors, yet my Zimmermans keep going.

I'm sorry. When someone yells THEY'LL CRACK THEY'LL CRACK I have to interject that in my personal experience that is not 100% true. Maybe they will crack someday yet. I don't know. At this point I've gotten my money out of them, so it's a moot point AFAIC.

The contention that they'll crack the moment the wheel is bolted up is seemingly a popular position with some people on this board, and my experience says otherwise. YMMV

PS the holes have never plugged up with brake dust either. WTF kind of pads are people using to get that effect?

sawood12

I'm not sure what pads they are running but I was running EBC Red Ceramics and I did notice a build up of dust in the holes - not completely blocking them but there was a build up on the trailing edge of the hole moving in towards the centre. I could very well believe that with pads that generate more dust than EBC Reds and using them harder that the build up could very well completely block the holes.

turboted

Agreed...cross-drilled rotors are prone to cracking, as there is plenty of evidence to support this. But only under very extreme conditions, i.e. track/racing situations. Even so, I know plenty of track warriors who have never cracked drilled rotors. For track duty, slotted rotors are superior to drilled rotors, IMHO. However, if you only plan to drive the car on the street and/or occassional track use, drilled rotors are superior to solid rotors. Just my $.02.

944CS

If you run an aggressive enough pad, you can crack a solid Porsche rotor. Porschephile, I have them on my car, they are balanced like the factory rotors, the quality is great. I got them because they weigh less, look cool, were cheaper than factory rotors, and for what I use my car for, they'll work the same as the stock porsche rotors.

Also, most (probably all) race tracks don't have a ban on street cars running drilled rotors.