rotor disc performance questions, inquiring minds want to know Options

[orange914]

O.K. so disc brake performance has so many different aspects. Add your experiances and wisdom to the question below

Starting with the solid vrs. vented... venting, heat, weight, stopping performance, off gasing, strength

My main question is what exactly are the performance pro's & cons of each:
A] slotted
B] dimpled
C] cross drilled

Summit refered to this and it made my wonder (IMG:style_emoticons/default/confused24.gif)

[tscrihfield]

O.K. so disc brake performance has so many different aspects. Add your experiances and wisdom to the question below

Starting with the solid vrs. vented... venting, heat, weight, stopping performance, off gasing, strength

My main question is what exactly are the performance pro's & cons of each:
A] slotted
B] dimpled
C] cross drilled

Summit refered to this and it made my wonder (IMG:style_emoticons/default/confused24.gif)

Slotted, dimpled and cross drilled rotors are all a part of a way for the adhesives in the brakes to outgas. However, since the newer brake compounds generally don't outgas the way they did years ago this feature is not exactly needed. I would stray anyone away from drilled rotors simply due to how often they crack. A nice slotted rotor will dissipate heat and stay stronger longer.

Just my $.02

Thomas

[ArtechnikA]

Slotted, dimpled and cross drilled rotors are all a part of a way for the adhesives in the brakes to outgas. However, since the newer brake compounds generally don't outgas the way they did years ago this feature is not exactly needed.

It's not all about green fade, which was a small part of a pad's life and done with after proper bedding.

Mostly, it's about rain, and to a much lesser degree, about the friction material vaporising from the heat.

Once you've driven a car with some kind of surface manipulation in the rain, you won't want to go back. You don't need to spend a few revolutions (at about 6' a rev...) wiping the water off, you get stopping right away.

In The Day, drilling was cheap & easy, once you have the proper pattern, and race cars replaced disks every race or so (endurance cars sometimes -during- the race) and get inspected *a lot* for cracking.

Nowadays, CNC machines make it possible to machine nice slots at production speeds. I think the logarythmic-spiral is probably the hot setup, but slanted straight slots are way more common.

If you drive where there is rain (I do) slots will help you. I have them on all my cars. I wouldn't drill a solid disk. Motorcycles do it, but they're exposed for easy crack inspection. I've had drilled vented rotors on many cars without issue, but cracking is something you have to be aware of. OTOH - disks are wear items and you have to replace them periodically anyway. If they reach the wear limit before cracking occurs, it's no issue. Get good rotors and you'll have fewer issues.

I have also had excellent results with cryo-treated rotors, but that's a different subject.

[underthetire]

Motorcycles use steel rotors, not cast iron or sintered steel, so they can get away with drilling, or through slotting. I agree with the no drilling of stock rotors, but slotting can be done on both manual or cnc machines almost equally easilily. The spiral slotting is a whole lot easier on cnc. I do have a guy local that can do them in his garage, he has a decent cnc bed mill in his garage if you need it done.