Why are discs cross-drilled?

[imdying]

Yep, and saving weight... check out the rear disc of Haydens RC211V (and presumably the 212)... freakin thing is the size of a dinner plate and made of Swiss cheese.

[Coldrider]

The sales blurb on petal discs is orientated at better cooling, thus less warp prone, and a bit of fashion as well, bling, but I'd have one or two of them.

[Pancakes]

I guess the fancy 'petal' type disks on newer dirt bikes are for similar reasons? To get rid of the water? Would they help get rid of grit as well?

Richard

I understand the petal ones are to help eliminate warping, cross drilled increase surface area for cooling and slots are for sweeping pad gasses.

[limbimtimwim]

Moto GP bikes use carbon brakes which are completely different as they have to get hot to start working well.

Aye, but they (Used to anyway, perhaps the technology has improved) swap them out for steels when it starts to rain.

[Pancakes]

I'd say they would swap them out. Have you ever used full on race brakes? Did a few laps in a hard core Audi once, nothing there till they were good and hot! Like rubbing two stones together with your hands. I think the carbon discs (and pad have a specific operating range too) run over 1000 degrees C!

[lordandrevv]

i heard of a horror story involving a bike once caused by a failing disk.
I think there was a picture of the aftermath on sportbikerider.co.us (and the story in the description). The front disk got so bad when it was abused that it cracked and warped, enough to stick out a bit and hit the caliper/pad and sent the rider over the top of the bars. Can't remember what happened to the rider, but it was pretty bad. I can't remember what bike it was exactly either, but it was fairly newish (mid 90s) and 1L
Jmtcw
Andrei

[skidMark]

You'd be hard pressed to find a modern road bike with grey iron disks. They are made of alloy steel which has little chance of cracking up. Strangely enough though some race bike disks are cast iron becuase it had alot better braking/friction properties. Moto GP bikes use carbon brakes which are completely different as they have to get hot to start working well.

I always thought the cross drilling was to provide a greater surface area and turbulence for cooling.

hmmmmm

my brakes in my honda civic cage...and even on my zxr too are always rubbish when they are cold...i find them alot better when they have warmed up abit.... go figure :S

[Pancakes]

You can get race compound pads that will do what your saying, I used to race shitter rally cars (doing club climbs and grass events and some trackdays) and instead of spending money I didn't have on race discs I'd use normal ones. I did have to change discs and pads at the same time tho! Good budget upgrade, the brake and clutch place in Takapuna have a good selection at a sweet price.

[skidMark]

yer gets dodgey first thng in the morning heading to an intersection at like 120 and having to engine break it like a mofo...my poor wee gearbox...

and yes learnt that lesson once....so i just take it easy until they warm up lol just gotta be careful not tov get em too hot....

cus den they no workys **dusnt even wanna think about it**

i never go cheapass on tyres and breaks

they are the most important things on a bike

it's your tyre choice and brake choice that will make the difference in that oh %#%^#$%$ moment

[Pancakes]

Wouldn't take great brakes to slow your new bike from it's top speed tho eh Mark? hehehehehe