The Best Material and process to make a Brake Disc

[oz]

I am having a few problems with the braking system on the CBR i wont go into detail as it isnt that important but the cure seems to be a larger Disc being made for the rear end,I have the facility to get one punched on a CNC Punch but distortion of the Disc may be a Problem maybe not If I can get one Punched what would be the best material to have it punched from Stainless steel /Mild Steel/High Carbon Steel,
or would it be better to have one spark eroded/Laser cut so it stays flat.
Cheers Oz

[McRat]

Never made brakes from scratch, but I was a machinist for a couple decades in a previous life.

Unless you buy ground stock, sheet metal or raw stock is not flat enough to use "as is", plus you want to "descale" the surface by removing at least .010" from each side if it's raw stock.

If it were me, I'd start with ground stock, then mill it on a rotary table,  or CNC mill, or water-jet, or laser the pattern on it (any method will work), EDM is going to be the most expensive and you will want do it "wire feed".  Make sure you use coolant during machining to reduce warpage.  Then check for flatness on a surface plate.  If it's not within .010" TIR (high low flatness), then either straighten it on a press, or better yet, surface grind it, or turn it on a lathe.  Surface grinding can be tricky sometimes, depending on the thickness.  If the disk is less than ~.187 thick, the surface will "pull down" when you turn on the mag chuck, and the flatness won't change.  So you will need to check it with a surface gauge or height gauge, and shim it in areas that it pulls down.  For LSR, thicker disks should be better.

Might be easier and cheaper to find an existing disk that is the correct dia, then make an adapter to mount it to your existing hub.  Or get a caliper with a bigger swept area.

Can't help much with material alloy.  Cast iron is the most stable common metal (won't change shape when it heats), but not sure what they use on newer bikes.

[panic]

"Might be easier and cheaper to find an existing disk that is the correct dia, then make an adapter to mount it to your existing hub" - Yes.

Material: cast iron.

[manta22]

Yes, the favorite choice for brake rotors is cast iron. With the thousands of styles of rotors that are out there, surely you could find one that is close enough to use-- even with an adapter.

Regards, Neil  Tucson, AZ

[hotrod]

Are any of these standard rotor sizes suitable?

http://www.stoptech.com/products/rotors.shtml
http://www.stoptech.com/products/img/0605AeroRotorDataSheet.pdf

http://www.brembo.com/ENG/Racing-Brakes/

http://www.dba.com.au/2006/default.asp

http://www.ebcbrakes.com/

Most of the major brake manufactures have generic rotors you can build  a custom hat for to mount to your hub.
If I were you I would spend some time talking to a couple of the major brake suppliers and see if they have an off the shelf rotor that fits your needs.

You did not mention the nature of your stopping problem but it might not be the rotor, could be clamping force or flex on the caliper, and or brake pad compound.
There are lots of things that effect stopping ability and the disk is only one of them.

Larry

[bones]

Oz, I have made discs from 'sg iron' for my road race sidecar which worked verry well. SG will bend before it brakes due to the spherical grain structure.You will need a foundry which is happy to do oneoffs.Make a pattern slightly bigger than you need and give the diameters some taper to pull out of the sand.Then bung it in the lathe and machine to suite. I have  also had success with alfeta car discs, about 10" dia and flat with 4 mounting holes.
cheers Bones

[Stainless1]

Brakes I thought you were building a LSR bike....

We used a hard anodized one for a while, worked OK for the pits but didn't hold up when used at 100... 

Now have a ground steel, seems to work when used.   

[oz]

Thanks Guys
The problem is alot to do with myself and needing everything to be "just so". I havent actually ridden the bike as yet and had a real bad weekend working on it,The engine had to come out again and it was dropped on to a lump of billet Aluminium there was a nasty crunching sound as it hit the deck and as i jumped up to inspect for damage in the sump area smashed my glasses into three or four bits so for all intesent purposes i was blind for the rest of the day and havent been able to inspect for damage as yet.serves me right for trying to rush but the clock is ticking.

 The problem with the brakes is on the particular model that i started with it had a linked braking system which at the best of times aint too good and the last thing that you would want on the Salt.
So my original Idea was to ditch the rear 3 pot floating item as there aint enough room to mount it in its normal above the Axle position, for a Suzuki GSXR Item Nice,Compact,reasonably powerfull and underslung so I made the mounts and tried it the problem is that the mounting Bosses are alot larger P.C.D and foul the rear piston and if I make a new mount the pads will be off  the disc by around 6.5-7mm which I dont like the look of as it will load the pistons unevenly and could nip up.If you are going to do something it should be done right or not at all dont you think.
Unfortunatley there isnt really alot of room at the rear to make any kind of adapter plate and the problem would still remain of the oversized P.C.D. its easier to make it bigger but a bit trickier going down in size.
It looks like i am going to give the ground Steel a go or in this case Turned,and see how I get on its worth a try I reckon.
If not I will try a few supliers and see if and how much a one off will cost.....Last resort though as finances have to be geared towards getting to the Salt now.
And the only reason for the brakes is for the regulations really and it may help on the road "er herm" Airfield tests as our roads oops Airfields dont tend to be quite as long or straight a yours.

Thanks for your help guys Cheers Oz
 

[maj]

What about just removing the Link bit of the brakes, there is still an independant section of the caliper that works fine on its own.

[oz]

Problem Sorted I tried the spare front disc on the rear and lo and behold same PCD I really should have checked earlier its a bit big and will probably be a bit too powerfull but beggars cant be choosers it looks ok on aswell

Mounting Brkt Mk2



Sits Nice on the Disc which has turned out to be slightly warped but the local breakers have plenty Honda spares to choose from.

[McRat]

It's easy to reduce braking power.  Just mill the pads so they have less contact area.  Or shorten the brake lever length.  Pads are easier because experimenting is cheap.  I had to do that to an AutoX car that would lock the rears prematurely.

[1212FBGS]

warped disc are ok... they push the pads back in and help from the "oh crap" brake lock up.... you just have to pump it a couple of times to get the pads back out..
kent

[Grant Borman]

Just for a data point i work at an Indoor Karting facility every now and then as a mechanic and the new karts we run use a steel rotor that was cut with a cnc plasma cutter(and this is from the French of all people!).  Its somewhere around 8mm and works fairly well but like what everyone else is saying i'd recommend finding another off the shelf rotor or pad.

Good Luck!