Tonykwok

iTrader: (3)

Cross-drilled rotor were invented when brake pad compunds released gases when they were hot. (outgassing). The gas pressure actually pushed the pad away from the rotor surface. Cross-drilling allowed a passage for these gases to escape However, modern brake pad compunds usually don't release gas under load, so you usually don't need cross-drilled brake rotors. If rotor holes are drilled instead of cast (this includes most corss-drilled aftermarket rotors), the rotors are prone to cracks and utimately failure around the drilled hole.

Slotted rotor....
A groved or dimpled rotor surface may make brake less likely to glaze (crust over with burned material) under high heat. But these features are more of a marketing gimmick then a benefit to the performance-minded enthusiast. They look coool, but grooves and dimples work like a cheese grater on the brake pads, weaing them more quickly than a smooth surface rotor.

2-piece floating rotor-
These rotors generally cost more than traditional one-piece cast rotors. The benefits that you can expect to see with 2-piece floating rotor include, quicker suspension response from the reduction in unsprung mass, less gyroscopic effect under turning, and possibly even quicker acceleration from a reduction in rotating mass.

So..2-piece floating rotor

Assassin

iTrader: (4)

Dang. Good post.

Anarchy99

iTrader: (196)

Then why do 90% of all Race cars have Slotted Rotors, IE Nascar, F1, Indy and Daytona Prototypes?

TKVK1

I think it's because F1 cars are prone for racing. Slotted or drilled might have minor benefit when driven under extreme condition. The rotor that were used on race cars might have differ from what u can buy??!!!
+ Race car changed nearly everything after each race....So they wouldn't care anyway.
Drilled and slotted rotor are not for average joe like me?! (does no good other than wearing down the pads faster)?

DanJ

iTrader: (2)

What are those brakes that are options on some high end porsches and come stock on the porsche carrera GT. It's like graphite polgycarbon something something (i probably butchered it). But from what I heard they don't wear out at all and will last as long as the car. I want those for my evo.

TKVK1

yeah, but those brakes on the carrera GT cost more than our evos....
Porsche offer carbon brakes?! and it's like 20g+

althemean

iTrader: (5)

I thought most of this was common knowledge? For car enthusiats I guess.

Good for throwin the info out again......

infantsam

iTrader: (1)

link?

hotrod2448

The slots do help deglaze pads as said before they do wear pads quicker than a normal smooth rotor. That is why most racecars use a slotted design.

The only potential advantage to drilled rotors is at racetracks where you don't use much brake and still need to accelerate off the corners or where saving every little bit of rotating weight helps like drag racing. The main downside to these besides less surface area is they are prone to cracking under severe use and heat cycling.

Another advantge to a 2 piece design is that they allow the rotor to float on the hat allowing for heat expansion and even wear.

hotrod2448

http://www.performancefriction.com/pages/rotors.htm

These guys supply most race series and just about all major teams with some type of parts.

Just about every thing we have from them is some variation of being slotted.

I'm not going to say 90% but alot of the good teams do.

infantsam

iTrader: (1)

I spent time w/ Brembo Racing at the PRI show - the last one in Indy - Ashley Paige I believe. He said it was a mix - some did -some didn't. He also said that dyno testing didn't show much difference - perhaps a slight torque increase.

Dyno testing my company did showed that drilled and slotted rotors got hotter and had longer stopping distances. Akebono did the tests. Pads wore 5 times faster too

At the highest levels I'd say wtf....someone else is paying anyway so who cares. At lower levels of racing rotors are typically the cheapest blank you can find - because they use em up so fast and it's not the difference between winning and losing.

For a street car they are really just a bit silly - but then so is a lot of things we do like clearing headlights. But clearing headlights doesn' tmake the bulb burn out faster.

For EVO's you have a distinctly different scenario- the slotted are cheaper than regular dealer blanks. Dunno why - but it is what it is. So at the end of the day - slotted it is!

el producto

iTrader: (2)

What about warped rotors, dont the drilled and slotted prevent warpage, besides that stupid gas emission from the break pads????

infantsam

iTrader: (1)

No they don't

And warped rotors are something of a myth - it's uneven pad deposits that are much more common - sometimes a really hard shaking at highway speeds - it's basically a very thin bump on the rotor. You can overheat a rotor and give ti 'hard' spots - but that might be unlikely with street or mild track pads unless you are intentionally abusing the brakes

I think I'm seeing more incidences of poor transfer layer (uneven pad deposits - same thing) with machined rotors than smooth.

hotrod2448

I used to see Gary Congi from Brembo at the shop pretty frequently but, now we use mostly PFC and AP stuff. We still have some Brembo stuff but, they seem to have fallen behind in some areas compared to the other two. The way the heat is distributed through their rotors is not as good as the PFC stuff that we use. I'm not saying there is anything wrong with them for street and most track use but on the brake dyno we could see some large differences with the thermal camera from one brand to the other.

When you say a slight torque increase I'm assuming you are talking about on a chassis dyno not a brake dyno. I think you would have a hard time seeing the difference between rotors on a chassis dyno.

The pad transfer issue has been covered at great length on this forum several times.

infantsam

iTrader: (1)

Boy I'd like to witness some of that testing - glowing red discs and brake smell for the win! I will admit that the whole demarcation between Brembo Racing and Brembo street (Race Technologies) is a little weird.

In some street cars Brembo went to the pillar vane design - i can't decide why I think they did that. They also seem to miss the boat on all three Brembo cars that are now out (EVO/STi/Z/G) - as well as more coming. They are losing in the aftermarket big on replacement rotors because of the ridiculous price and complete lack of marketing. The Brembo STi rotors barely sell at all.

Brake dyno for sure - I like the way Brembo does the pre-burnishing.

Since vane patterns on the rings aren't tremendously different I'd again want to know why the PFC or other discs do better. Is it the type/alloy of gray iron or is the vane configration that sensitive. Those beefy Nascar 1.25" thick 48 vane boat anchor rotors sure look good.

Well that was a little OT - sorry

I've worked with/watched several guys who run slotted w/almost full race pads - Quite a few times they are hard to bed right - get pulsing etc. And you can see the carbon smearing off the trailing edge of the slot. I'm not up to full race pads yet - but my smooth rotors thus far have been doing well. I got some judder in one session - but then it went right away by the next session. And the wear pattern is nice and uniform. Thats why I'd say stick to plain if you can.