# Slotted rotors..Rice????



## PatScottAKA99XE (Apr 30, 2002)

What do you think?? Take this into consideration:








Xanavi GT500 Skyline


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## McLaren F1 2003 (Jan 2, 2003)

PatScottAKA99XE said:


> What do you think?? Take this into consideration:
> 
> 
> 
> ...


see that car actually makes use of the slots...

i think you should only put cross drilled and/or slotted rotors on street cars only if you use that same car for road racing or autocrossing or something like that


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## B11sleeper (Oct 15, 2003)

cross drilling rotors is really not needed dor most cars ever. slotting is useful. drilling small rotors makes them crack, and if they get that hot you need a different brake setup.


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## sno (Oct 4, 2002)

slotted rotors aren't rice, they're functional.


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## samk (Feb 26, 2003)

i dont think getting slotted rotors is a rice thing to do


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## Slayer2003 (Jun 4, 2003)

damn, like, when i first joined here, i had maybe a 4-page argument with some guy about this. i even gave racing application examples, and it was still considered "rice". times change i guess.....


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## ReVerm (Jan 13, 2003)

Slayer2003 said:


> damn, like, when i first joined here, i had maybe a 4-page argument with some guy about this. i even gave racing application examples, and it was still considered "rice". times change i guess.....


Actually the guy who you were arguing with was incorrect with his counter-examples. Many racing teams use cross-drilled and slotted rotors, even JGTC cars (and no, they don't use ceramic on ceramic). Slots clean the leading edge of brake pads, drilling helps with that and initial bite. This all depends on how the holes are drilled and the slots are cut. He was correct in saying that a lot of manufacturers screw up the way they drill/slot their rotors though.

In the end, it's all a matter of whose rotors you buy and what you do.


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## morepower2 (Apr 19, 2002)

PatScottAKA99XE said:


> What do you think?? Take this into consideration:
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> 
> 
> ...


My race car uses slotted rotors!

Mike


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## sethwas (Apr 30, 2002)

My bike has slotted rotors.

OK, no it doesn't, but i've seen it.

Seth


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## spdracerUT (Jun 11, 2002)

I've seen a lot of race cars, including indy cars, and most use slotted rotors. I haven't seen a single real race car that uses cross-drilled.

All sportbikes (street going ones that is) do use cross drilled rotors. I think MotoGP bikes use solid carbon fiber rotors or something. Anywayz, I don't think they get as hot as rotors on cars (considering they are totally exposed and rotating in the airstream). 

It's my guess that they use cross-drilled rotors to reduce rotating mass. This is very important considering the front wheel acts as a big gyro and any extra rotating mass will slow down the bikes ability to lean over. And considering how much airflow the rotors get, they probably don't have to worry about cracking. I did a test on my bike where I got on the brakes hard on my bike, rode around for a bit and touched the rotors to see how hot they were. They were not hot at all. Tried the same thing with the car, and I would've ended up with burnt fingers if I had touch them for more than a nanosecond.


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## ReVerm (Jan 13, 2003)

spdracerUT said:


> I've seen a lot of race cars, including indy cars, and most use slotted rotors. I haven't seen a single real race car that uses cross-drilled.
> 
> All sportbikes (street going ones that is) do use cross drilled rotors. I think MotoGP bikes use solid carbon fiber rotors or something. Anywayz, I don't think they get as hot as rotors on cars (considering they are totally exposed and rotating in the airstream).
> 
> It's my guess that they use cross-drilled rotors to reduce rotating mass. This is very important considering the front wheel acts as a big gyro and any extra rotating mass will slow down the bikes ability to lean over. And considering how much airflow the rotors get, they probably don't have to worry about cracking. I did a test on my bike where I got on the brakes hard on my bike, rode around for a bit and touched the rotors to see how hot they were. They were not hot at all. Tried the same thing with the car, and I would've ended up with burnt fingers if I had touch them for more than a nanosecond.


A lot of touring cars use cross-drilled rotors. The holes aren't (or rather, shouldn't be) enough to reduce rotational mass. They're there to scrape the pads clean, allow gasses to escape between the pad and rotor surface, and help the pad's inital bite.


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## PatScottAKA99XE (Apr 30, 2002)

morepower2 said:


> My race car uses slotted rotors!
> 
> Mike



What advantage do you see in using them?


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## spdracerUT (Jun 11, 2002)

ReVerm said:


> A lot of touring cars use cross-drilled rotors. The holes aren't (or rather, shouldn't be) enough to reduce rotational mass. They're there to scrape the pads clean, allow gasses to escape between the pad and rotor surface, and help the pad's inital bite.


Hmm... interesting. I haven't seen any touring cars with cross-drilled. If you look at motorcycle rotors, they're only about 1/4" thick discs and my guess is the cross-drilling removes maybe 1/6th-1/8th of the material. That's a significant percentage of mass.

The new Kawasake ZX-10R has these funky shaped wave rotors or something. Marketed as having reduced mass. So when it comes to bikes at least, I think the cross drilling serves a reduced rotational mass role. 

I wouldn't use cross-drilled on a car because extreme thermal loading will lead to cracks. Even the factory Porshce cross-drilled rotors crack.


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## ReVerm (Jan 13, 2003)

spdracerUT said:


> Hmm... interesting. I haven't seen any touring cars with cross-drilled. If you look at motorcycle rotors, they're only about 1/4" thick discs and my guess is the cross-drilling removes maybe 1/6th-1/8th of the material. That's a significant percentage of mass.
> 
> The new Kawasake ZX-10R has these funky shaped wave rotors or something. Marketed as having reduced mass. So when it comes to bikes at least, I think the cross drilling serves a reduced rotational mass role.
> 
> I wouldn't use cross-drilled on a car because extreme thermal loading will lead to cracks. Even the factory Porshce cross-drilled rotors crack.


That's interesting. I know nothing about motorcylces or motorcycle racing, so I learned something.  

Specific examples of cars which use (or rather used. I don't know about the 2004 cars) drilled rotors are RE Amemiya's GT300 RX7 and Proton's old BTCC Satria. Cracking isn't nearly as big a concern because rotors are replaced pretty much every race since they're wear items anyway. You're right though, most teams have been going to just slots. Even the WRC cars all have just slots now.


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## Jdm95Se-R (Feb 29, 2004)

Alot of the race cars that I see use only vented rotors, I'm sure that is because the materials they make their calipers/rotors out of disapate heat better. But on cars like ours that we can't use precious (read-expensive) metals so we have to resort to cross drilling and slotting, because it does disapate heat. But on small rotors like ours the rotor will prob crack in between drills if they go through enough heat cycles. Chad.


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## ReVerm (Jan 13, 2003)

Jdm95Se-R said:


> Alot of the race cars that I see use only vented rotors, I'm sure that is because the materials they make their calipers/rotors out of disapate heat better. But on cars like ours that we can't use precious (read-expensive) metals so we have to resort to cross drilling and slotting, because it does disapate heat. But on small rotors like ours the rotor will prob crack in between drills if they go through enough heat cycles. Chad.


Umm.. Cross drilling and slotting don't do a great job of dissipating heat. Most modern cars also have vented front rotors, even my cheap base model 200sx.


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