Turn a Maxim disc?

Anybody know if a stock xj650 maxim single front disc can be turned or ground? Seems like I read something about them being too hard a metal.

 

I have been told that they are to hard for the lathe, but i have been thinking about checking with the machine shop, and seeing if the flywheel grinder might do it.

 

I'm a bit surprised by that... weren't they lathe-turned in the first place? Brake lathes use carbide cutting inserts - usually C-2 grade. It may be that these steel rotors are a bit harder than regular automotive rotors, which are cast iron, and the shop that said they were too hard either didn't have the higher grade Cermet or TiN bits, or they just felt that they'd put too much wear on a set of bits turning steel.

 

Yes, it can be done; but they have to be Blanchard-ground, and preferrably both sides at the same time. I sent mine to a race-car brake guy who advertises on eBay and had it ground and drilled.

The biggest drawback is that there is very little "leeway" between the thickness your disc is now and the minimum thickness. The grinding can't take more than a few thou or you go too thin, so the rotor has to be in decent shape to begin with.

Do a forum search, we had a BIG DEBATE about this a while back when I got the rotor for my '81 ground and drilled. There are strong and valid opinions for both sides, some say it's a complete no-no.

I've got over 3000 miles on it now, and no cracks or ill effects at all.

This was taken right after it was installed, before the SS lines went on:

 

nice Bigfitz-if you don't mind,how much did it set you back?

and does the drilling make a diff only in the rain or on daily rides?

 

the rigidity of the bike disk is most likely why brake lathe isn't the machine to use
as the cut goes to the outside the disk will try to deflect away from the cutter, a car disk is rigid enough to resist this but a bike disk will flex and start to chatter
i never ran a brake lathe but the spindle speed and feed speed are most likely setup to cut cast iron and would be different for steel, compounding the chatter

 

Like I said, when I originally posted about it I thought it was really cool; then we had a big debate because of the need to do the grinding correctly so it doesn't heat-stress the disc unevenly.

Since I already had it done and on, I've been inspecting it frequently during the new pad break-in period and subsequent miles. No issues.

I don't remember for sure the guy who did it, he was advertising on eBay; it cost me $70 shipped and he had it back to me in a week. I can dig up the info, it's in my email archive at home and I'm at work.

Once again, it's important to remember that this process doesn't have much to play with, it can't correct a badly worn, scored or warped disc. The difference between new and minimum thickness isn't very great, so you have to start with a pretty decent disc to begin with.

As far as the performance goes, I was having a really drastic fading situation in summertime rush hour traffic. The drilled disc (with brand new Yamaha pads) seemed to nearly completely eliminate the problem.
I haven't been caught in a heavy enough downpour yet to tell how much difference it makes in the rain.

I have since installed stainless lines and the brake is now flawless.