Brake rotor questions. Maybe guinea pig Dave can help here.

[KDXer]

I need a new REAR rotor and got a rude shock at the price. $200AU starting price. I found this website and have a few questions.

http://members.ozemail.com.au/~smiley_b1/About.htm

I have a mate who can get anything upto 20mm thick S/S laser cut. I would have to source the material, give him that along with my old, worn rotor and he will cut them for free. I have looked into the materials used and wonder if a high grade stainless would do the job ?? As in something less (read: cheaper) than say 420 grade. Here's a great site with S/S info.

http://www.alleghenyludlum.com/pages/pr ... oducts.asp

Has anyone heard of anyone making their own ??

I have a few more questions but will leave it at that for now to avoid confusion.

Any help would be greatly appreciated... Cheers... Trev...

[KDX220PHIL]

I believe 420 SS heat treated is a common grade used for discs. How do you plan on achieving the + or - .0005" flatness and parallelism between faces of the disc? This is a fairly tight tolerance, and is usually factory ground to achieve probably more like + or - .0002".

[KDXer]

I don't frikken know !!! Seriously though, I figured flat S/S plate would be, well, flat. I think they just claim those fancy tolerances to sound more fandangled and edjamacated... I have heard of a few guys over here simply getting them laser cut and having pretty good results. I guess time will tell.

[m0rie]

Trev I know there is the whole other continent, import charge deal but would it be cheaper to pick up one of these:

http://www.rockymountainatv.com/product ... vType=type

from Rockymountain and have it sent down your way? Heck maybe pickup 2 so you've got a spare? I've got one on my 89 and it seems to be holding up fine so far.

-Maurice

[KDX220PHIL]

Trev, i checked the tolerances of the plate, they are not adequate for rotors. Tolerance of flatness, parallelism, and surface roughness are too great. If your friend has access to a grinder or even a lathe (with experience), the tolerances can be achieved.
I havn't changed my brakes yet on the KDX but do you know if the center hole of the disks locates on a mating diameter on the bike? If so, there will be a tolerance for the perpendicularity of the center axis of the hole to the contact face of the rotor. Hope you get that, a little Gemoetric Dimensioning and Tolerancing for ya.

[KDXer]

Yep, I looked into that also, thanks Mo and Jas. Because my mate can laser cut them for me (read: FREE) I'm going to give it a go and see how it turns out. I have a few contacts in different steel merchants so hiopefully material will be relatively cheap. If all else fails then I will send the guy in the first link an email requesting prices and go from there.

[KDX220PHIL]

Great, I look forward to hearing how it works out, might try it myself if all is good.
Maybe Dirt bike rotors are more forgiving to inconsistencies in flatness and thickness than car rotors. My car rotors were out by a copuple thousanths of an inch and caused my car too vibrate like mad.

[KDXer]

Thanks for that info Phil, very informative... I had thought about taking the cut rotor to another mate who works at a place where they can machine car rotors to see what they say. I don't know if their machinery can even accept bike rotors, but a possibility.

[IdahoCharley]

I think your approach is workable..... Cutting the appropiate holes, centering of the hub holes etc should be very easy if you supply the used disc. Especially if the laser cutter has a pattern tracing program.

Not everyone has surfacer grinder access but chucking it up in a lath and refacing (read - truing the parallelism between the faces) is how a number of performance shops perform the work on disc brakes for high performance car brakes.

I don't know where you should go to determine the best SS for this use; but I wish you well in this endeavor. If it works out maybe you and your buddy need to make a few to sell to your mates.

[dave04kdx]

Brake rotors are a finicky thing. They MUST have some run out in order for the brake pads and caliper pistons to be retracted after braking. Too much run out and you get shaking when the brakes are applied.

Good luck with your project Trev!

Keep us posted on the results.

[KDXer]

I think your approach is workable..... Cutting the appropiate holes, centering of the hub holes etc should be very easy if you supply the used disc. Especially if the laser cutter has a pattern tracing program.

He said to give him my old disK or at the least a photocopy of it so I presume (read: hope) it has a pattern tracing program.

Not everyone has surfacer grinder access but chucking it up in a lath and refacing (read - truing the parallelism between the faces) is how a number of performance shops perform the work on disc brakes for high performance car brakes.

Cheers I will look into that also.

I don't know where you should go to determine the best SS for this use; but I wish you well in this endeavor.

I think I have the material covered, a few phone calls tomorrow will either make or break this idea. I really need to find out roughly the thickness of a new / near new rear rotor... Try saying the last four words from '/' 10 times fast with 4hrs sleep. Thank you for the well wishes.

If it works out maybe you and your buddy need to make a few to sell to your mates.

That'd be the idea of it, 'mate'.....

[KDXer]

Run out = ????

Un-even-ness ???

[KDX220PHIL]

http://www.engineersedge.com/gdt.htm

Check Runout, i don't know where you will find the specs, possibly lie to a manufacturer of the disks in an attempt to retirieve them, haha.
This can be checked with a dial indicator and magnetic base, failry simple.

[KDXer]

The guy in my first link makes them himself so I may well try and ask him in a round about way. EG. "Hi there I am interested in your brake rotors and wondered how close to original factory specs your rotors are made ?? IE runout, Thanks Phil, Dave and IC for your help and comments. It's starting to sound like more trouble than anything but I will persevere for now and wait for 420 grade S/S sheet prices.

[skipro3]

You might as well have him cut wave rotors instead of plain circular rotors while he's at it. Or, carve KDX in the rotor in place of the slots. That'd be cool!!

[KDXer]

I thought about the wave rotors (even oversized one's) but then I'd have to buy one anyway to get the specs etc. RE: KDX carving. I don't want to push the friendship just yet, but thats a great original idea I may look into after initial testing is over, if we get that far.

[KarlP]

A buddyof mine made a rotor for his XR400 exactly as you are planning - laser cutting table, the old rotor, and sheet stainless (not plate) I don't know the grade of SS, neither did he, it was some drop the shop had laying around.
Worked great from day one. He sold it a couple of years ago. As far as I know it is still on there. My buddy ran it for about 2 years.

Karl

[KDXer]

Why thank you very much for that info Karl !!!

[canyncarvr]

I'd think you could even it up with a sheet of wet-n-dry on some plate glass...kind'a like you do with a cylinder head?


Re: runout

Not because I know...but I'm sure that has nothing to do with pad retraction. Pad retraction has more to do with piston boot tension and more than that do with air forcing the pads back.

**edit**

Did some googling...

B. Retraction – The action of the brake pads being physically pulled away from the rotor. Typically hydraulic calipers use a rubber seal (square seal) that deforms when the brake is applied, and then returns to its normal shape and pulls the pads away from the rotor when pressure is released. A few hydraulic and almost all mechanical systems use springs to pull the pads away from the rotor.

That from:

http://www.hayesdiscbrake.com/hayesu_product1.shtml

I think Hayes knows somthing about brakes. Heck..I got Hayes calipers on my Duster!!









Oh...the first part was just a joke! I wasn't cirrus 'fer crine out loud!

[KDXer]

Oh I just went and bought some glass sheet too.


I spoke to a S/S expert and got a few ideas and prices. For a piece of 200 grade S/S (the 200 grade is as good for rotors as the 420 apparently but ALOT cheaper) it would cost around $200AU for a piece 2000MMx300MMx8MM. Should be able to punch a few out of a 2M length. I still have to get the proper rotors thickness before I can get a sample to make a prototype.