Who drills discs?

[Petrus Rocks]

I want to get my cast iron rotors drilled (3).  I'm in western NY near Rochester.   No idea how much it costs.
Anyone to recommend?

[dsrdave]

Are they new or used ???  I'm not sure why but I was always told not to drill used rotors (this was a solid rotor used for car racing) as they would crack.  That info may or may not apply to street use as the heat involved is much less.  If you go ahead with the project just make sure to use a qualified shop that knows what they're doing.  Good luck !!!!

[Antietam Classic Cycle]

Drilled my own back in '83.



Coated the whole surface with layout blue, then used dividers to lay out the pattern, center punched and drilled. Time consuming but inexpensive.

[RinkRat II]

Hey there PR,
   New cast iron, make sure the pattern is not symmetrical as it will groove your brake pads making braking less effective. All holes need to be countersunk minimum .0625".
   Old  cast iron, Forget it. They will crack as the Iron has already Seasoned and drilling will only weaken it.
   Steel or Stainless, drill away.

     PaulB :BEER:

[canuck750]

These guys do and for a pretty fair price

I sent them 5 rotors a week ago by mail from Canada and they emailed me yesterday to say they are already done and being returned by mail Monday, very fast turn around.

http://www.truedisk.net/

[Petrus Rocks]

Talked to Tom at Truedisc.  He was very helpful, thanks Canuck!.  He said he could drill and grind them for $80 each which is a fair price.  tom said the cast iron was no problem- he has done hundreds of them.
Now i have to sell more stuff so i can buy M/C parts!

[yackee]

What is the benefit of drilling them? (A question borne of my own personal ignorance). Something to do with heat dispersion?

[Petrus Rocks]

Discs are drilled to lighten them and increase their braking ability in wet weather.  They also might cool the pads a little.  The lightening means less unsprung weight for the forks and shocks.  They are better able to dampen with less weight to have to move up and down.

And they look cool.

Part of the service this company offers is grinding- they make sure the discs are flat and the surfaces are parallel. 
This means a better friction surface for the pads.

[yackee]

Interesting. Thanks for the info. I was thinking that if you drill them you have less surface area in contact with the pad, and that at least dry braking would be worsened.

[rodekyll]

With disks the issue is swept area, not surface area. 

With rotors 5mm thick you're not going to gain as much unsprung weight advantage as you would be washing the bugs off the fork lowers or using smaller axle nuts.  The weight removed from the holes is not that much.  If these were fat double-disks as used in some autos, you might get a few ounces back.

In my opinion the big advantage of drilling is to give dirt somewhere to go.  Scoring and grooving rotors, premature pad wear, pulsating brakes and squealing can all be attributed to dirt caught between the pad and rotor. 

[bigbikerrick]

What is the benefit of drilling them? (A question borne of my own personal ignorance). Something to do with heat dispersion?

I believe drilled holes also allow for expansion, and escape of gasses produced when the pads press against the disc, and heat is generated.
Rick.

[dguzzi]

and they look cool!

[Petrus Rocks]

I'll have to do a before and after weigh-in. 
I measure 6.5mm but that's pretty close- it's a percentage game, how much can you remove?