Cross drilled or slotted?

[Henka]

I had my mind dead set on slotted discs as crossdrilled crack. But then I started thinking.

Cross drilled

+ Lighter (like 40% roughly!!)
+ Bling?

- Cracks
- Looks like I don't know what I'm doing...

Slotted

+ Won't crack
+ Looks like I did my home work

- Heavier than cross drilled

Anyone care to comment? Nordmann bremsen has a crossdrilled disc for about €100 a piece and that won't be any more expensive than I'd have to pay for a set of stock A8 discs and having them grooved/slotted. And I absolutly hate excess weight, specially the kind that rotates and translats, y'all know... Help me out here, groovy or swiss-cheese-y??

[ThatGUY]

get both (slotted and drilled) . Then your in the middle

[90quattrocoupe]

I vote slotted.

[Henka]

Even with higher unsprung weight and mass inertia??? Won't the car feel slower??

[zlobo]

i am using driled and havent got any problems yet.

[Keeper of The Kitten]

I'll be going slotted only - for the reasons of cracking. Disc life is definitely superior, but even the brake manufacturers don't claim significant weight reduction (most street application discs have less holes than racing discs as they need to last longer, and it's pure bling).

Point taken about the weight though, especially if it's a custom weight reduction programme you're embarking on. Seriously though, the racers don't care about disc life and that's why the discs they use have lots of holes.

One other "drawback" of slotted is the extra noise - drilled are a little quieter in operation. I'm not especially worried about that!

__MDC__

[Keeper of The Kitten]

BTW, I reckon heavily drilled discs must be losing a lot of pad contact area - wouldn't this lead to less braking efficiency?

That's not proven, but in theory you can only have as much pad to disc contact as the size of the pad minus the area of holes underneath it, yes?

__MDC__

[WabTheKing]

here's one i slotted earlyer

[Greg_S]

I'd just go for grooved discs, when I was talking to Pete Collen who designs kits for AP racing he was saying that grooved is the prefered option, especially on road cars due to cracking and the drilled/cast holes weaken the discs more. There are lots of different groove patterns you can get, the merits of each im not sure there is much apart from looking different.

Drilled are usually made that way for looks

[curlyks2]

Swiss-cheese style for me, where the holes are cast in as part of the disc manufacturing process. Supposed to be less prone to cracking that holes that are drilled in after casting. E.g...

Ck.
PS Sorry about colour balance in picture: wasn't taken in great light.

[WabTheKing]

you mean their stress releved?, ie cast, drilled, heated, then skimed instead of cast,skimed,drilled

[Henka]

Someone stated that Porsches discs had cast-in holes - that is a pure myth! Zimmerman manufactures their (Porsche's that is) discs as Wab states...

[curlyks2]

The manufacturer of those discs says:

rotors are all vented with cast not drilled holes

BUT I imagine this could actually mean any number of things!

Ck.

[dan_b]

Get grooved discs - x-drilled is bling-tastic.