what metal are brake rotors made of?


I bent the heck out of the front rotor on my KTM. I straightened it pretty well, but it will never be RIGHT again. I hate to pay for a new one when I know I can make my own. Easy to design on AUTOCAD, then get laser cut. Then I can get it ground at my buddy's machine shop. The KTMs dont use a floating design so it's really simple.

The only technical hurdle is that I need to know what steel alloy to make it from. Please don't guess on this and tell me only if you KNOW- thanks.

Also, since 5-10 rotors would only cost slightly more than 1 rotor, would anyone want one? I will do all the work, just looking for someone to split costs to make it cheaper for all. I am making a front rotor for a KTM 525. It shoud fit all but the 620/640's, even 2 strokes.


I know it is stainless, but do not know the alloy. Texture when finished should be ground with a cross grain rather than lathe turned circular grain, in a perfect world grain is 90 degrees from the friction and as soon as the rotors become glazed they should be reground (like that guna happen) as this allows the groves of the texture to shear off a small amount of lining. Once those grooves are gone the presure requirments to make the brake (or clutch) work go way up and take the heat up with it!


Thanks for the reply. I did some research and most are stainless, but a Dutch company is making them in chrome moly (again, no specific alloys). I will continue to try to find specifics. You are right about the crosshatching, though all of mine are so grooved radially from mud, I don't think it will make a big difference. But I'll do it anyway, as I want to do it RIGHT.

I have had a few guys express interest in buying one. I am definitely going to make them, and even though I don't need a rear for mine, I think I am going to make a few, as I want a solid rotor anyway. I was going to do both front and rear in solid style (no grooves). I had solid rotors on a previous bike and the pads lasted about 100 times as long since mud doesn't get in the grooves and chew up the pads. I don't know exactly how much they will cost yet, but I will only charge what it costs me portion. I'm guessing right now it will be around $50 or less. If some more people want in on it, it will be less, of course. ANYONE? ANYONE?

Wouldn't it be much simplier to just order a Moose brake rotor ? Usually just under $99 and even cheaper if you sweet talk you local dealer.

Time and travel have to be considered in the price of having one made and cost of material.



I had some made from "mild steel" and some kind of "stainless steel" at my local laser profiling shop.

The stainless ones tended to pick up using sintered pads, not enough to ruin the pads or the disc, but enough to cause dramatic grooving of the disc surface.

The mild steel ones were a a much better braking efficiency, but went rusty where the pads did not rub. I wish I had found a place to give them a plated finish to stop the corrosion, but just settled with spraying the discs with oil and wiping them clean with brake cleaner before riding! Or looking for mud to ride through if I forgot to clean them !

Cost was about $30 one off design cost plus $10 material and cutting cost.

The quality of the rolled plate was so good that finishing by grinding was not required.

Thanks for the background. I tend to think you are right about the grinding, as they get ground by mud and debris anyway. I think that chrome moly would be a good compromise between the stainless and the mild steel you used. ChMo is fairly corrsion resistant, due to the high chrome content. I should have them in a few weeks.

Try Rocky Mountain's web site, nickle plated steel for discs for under $50.

Making them myself is much more fun, plus I am considering trying to sell them for profit.

The laser cutters are on the job! I should have them by next monday or tuesday. I originally designed them with the KTM logo cut out of the lightening holes in spokes, but decided against it, as I don't wnt legal problems.

I got them done- and they are pretty cool. Price per was about $38. I made them in 4130 CrMo, solid with no grooves to pick up mud and trash the pads and rotors. They should last FOREVER. I made 5 front and 5 rear. PM me if you want any at cost to make ($38 each). I will try to sell on ebay or something for more, but will sell to TTer's for cost.

I will post pics as soon as I figure out how...

I bent the heck out of the front rotor on my KTM. I straightened it pretty well, but it will never be RIGHT again. I hate to pay for a new one when I know I can make my own. Easy to design on AUTOCAD, then get laser cut. Then I can get it ground at my buddy's machine shop. The KTMs dont use a floating design so it's really simple.

Most are mde from 400 series stainless. I work as Mechanical Designer using

Pro/E and Acad. I made a few discs for my 200 EXC out of T1 prehard and had it laser cut at work (we also build out own lasers). Anyway, good to talk to a fellow drafter. The T1 is fairly expensive, but luckily we had a full sheet laying around. It will get a little surface rust on it, but not bad. It wears very very good also and has good grabbing characteristics. They will come in at about 38 to 42 Rc hardness and will work harden slightly making them last longer. I also come up with my own design making it in between a wave rotor and conventional KTM stock design. If you are going to draw it up, it would be good if you do it in manner so that no surface of the pad never gets interupted by a slot in the disc. Cleans the pad much better and allows it to wear evenly. Ever notice on wore rotor when it has a ridge about 1/16" around the outside where the pad doesn't touch it?

Grinding is best done on a Blanchard type grinder. That will allow for the best

possible pattern while still keeping it flat.

The material you selected should be good. Anywhere in the 4130 to 4150 range is good. You will get some work hardening in it too. I used some cold bluing on mine afterwards to keep inner part from rusting. The pad surface will rust slightly, but comes off the first time it rotates.

My last project was an auto clutch. I completely designed it in Pro/E and then machined it myself. Sometimes a hefty background in machine shop can payoff. Turned out really well. Now I just wished it had been for my bike instead of a friend's.

Ok, I have rambled on enough. Good job on the disc. Good luck with them.


so how did the rotors work out? did the 4130 material wear alright? any problems?

thanks, Verdeen

These prjects are very intersting to me. I wish I had the skills you guys have when is comes to desighning and machine work.

A word of warning. The "wave rotor" desighn is patented and they do enforce it. The patent is from a company in spain called Galpher. I just thought I would let you know as I know some one who ran into this problem trying to sell rotors that he made. Anyway, good luck and nice work.

I hope it works out for you, Looks nicly done, with that much grinder texture it should keep the lining fresh even without the slots. Chromemoly will rust somewhat (but not like mild steel), someone said spray them with oil, that would be a huge no no. Don't want any oil to get into the pads. I say let them rust, go ride and you will just have brown edges.

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