Dumb arse question

[latheboy]

Ok ... Are holes really needed on disc's ... what do they do really .. is it just air flow for keeping the temp down ?
And let the shit caning begin:D

[TurboKat]

I raced my XR Supermoto with a non drilled 300mm RGV front disc, the thing stopped like a motherfucker on the road or the racetrack. [^]
So..... I'm thinkin' if some is good, then more must be better - right [?] So I made up another adaptor for a 320mm drilled RGV disc, bolted it all up & went racing... guess what? it still stopped like a motherfucker but I'd be fucked if I could tell the difference between the 2.
I had a chat to a good mate of mine who builds Race Cars & he said he'd done extensive back to back testing of the same disc rotors drilled vs non drilled at various circuits & his conclusion was that for tracks that weren't hard on the brakes (P.I. & Winton) you'd use the non drilled because they were more effective with initial bite & retain more heat for shorter stops but on tracks like Sandown & Calder that were hard on the brakes, the extra cooling of the drilled rotors was necessary to stop fade due to too much heat retention.
If you rode like God himself, you'd need holy [:I] discs but for us mere mortals, solid is probly more than enough.
Dumb Arse ;)

[Deano]

they are to give the basically clean the pad. as the pad rubs against the disc you will get a build up of gases and dust betweent the pad and disc face.

as the brakes get hot you get a spongy feel been brake fade. the holes will help by basically facing the disc using the trailing edge to remove any dust from between the pad and disc giving you better brakes. would also create some area for expansion of air/gases traped between the pad and disc face as they are heated buy the pad friction.

they will help cool the disc better as there is more surface area and also less rotational mass.

they will not elimate brake fade but you may be able to use your brakes harder for longer before you feel the effects.

that my theory anyway

[Deano]

and your pads wont last as long with drilled and slotted because of the 'wiping lip' of the holes/slots

[Rocket]

And brake discs with holes in them are better for riding in cross winds [:o)]

[TurboKat]

I missed the main point, :( there is a fine line between enough heat & too much in a racing situation, in a perfect world, you'd have a balance between initial bite/power & heat buildup/fade resistance - eg. you want the pads to bite as hard as possible on first application without locking a wheel & still be able to have full braking power after a dozen laps of hard stops.
I've found there are big differences to be made in braking performance by swapping pad compounds, I only use HH compound these days coz I can't lock a front wheel if I accidently panic brake from cold & once they warm up, I've never had any fade.

That's a long way to go to answer your question, but no, holes aren't necessary for braking performance but discs with holes weigh less therefore can be made larger in diameter to increase brake torque whilst reducing unsprung weight.
Plus, they look gooder wiv 'oles in 'em.

[latheboy]

Wicked .. thanks guys ... to finnish the story off .. im making a set of disc's for a mate who has been given a GPX250 , so i drawd up a fancy looking disc but was unsure about cross holes .. and thanks to you guys im still unsure;) .. I think he can go without cross drilled disc's ... I might join a GPX forum and see how many i can flog :D[}:)]...
Rocket ... what size holes do you need for different speed winds:D

[BOHEMION]

Chain gang seem to go with a solid disk, how ever there not made from a common material
http://www.chaingang.com.au/discs.php

[BOHEMION]

http://www.chaingang.com.au/discs_points.php

[latheboy]

Thanks Bo .. Sounds like Bizalloy ... i had a disc made out of 316 SS and it was gay so i made another from 360 Biz and its bang on ..