Turning Brake rotors

[65chevelle]

I have 1982 GS1100G The rear rotor is a little rough and I have a brake lathe has anyone had a chance to try turning down a bike rotor? What pads should I use?

[Steve]

Measure the thickness of the rotor and compare that with the minimum thickness that is stamped on the rotor.

You may find that you don't have a lot of room to spare. Do you have a way to clamp that rotor in your machine? Many have tried with no success. There is a process that is used to surface-grind brake disk that works with bike rotors, but I understand that it's kinda hard to find someone that can use it.

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[rphillips]

I've had a few done, but the only place I could find to do it is a machine shop. None of the brake shops I went to wanted to fool with bike rotors. I think you will find the minium thickness advised by the Mfg. is stamped on the rotor. Wouldn't go too far past their advice, but use your own judgement. As far as pads, my opinion, for normal everyday use, there's not a lot of difference. Just my opinion.

[GregT]

You can reface your discs in your lathe - but only if you have a toolpost grinder. Your bike discs are a steel which does not machine well with the cutting tools used for cast iron car discs.
The provisos already mentioned still hold - don't go below the factory's minimum thickness.
Here in NZ this gets checked at the annual WOF inspection - your circumstances may be different.
I usually get a local machine shop to surface grind any I need done.

Greg T

[tlg1100]

Can new rotors be purchased anywhere,I might need some??

[Roger P.]

You can reface your discs in your lathe - but only if you have a toolpost grinder. Your bike discs are a steel which does not machine well with the cutting tools used for cast iron car discs.
The provisos already mentioned still hold - don't go below the factory's minimum thickness.
Here in NZ this gets checked at the annual WOF inspection - your circumstances may be different.
I usually get a local machine shop to surface grind any I need done.

Greg T

Agreed. I tried turning my 1100 rotors in a nice old Monarch lathe with good carbide bits, but the thin rotors like to "sing" a bit when cutting which leaves a very poor surface finish. If there was a way to damp this out, it might work, but grinding is really the better method by far.

[Counter]

I would be careful about turning your rotors. Rotors tend to warp more easily once you start turning them as you are removing mass from the rotor. I think it might be a better idea just to get replacement rotors (if they are easily found). Of course, I don't know what a replacement rotor costs...

[Road_Clam]

I machined my GS rotors. Not the greatest finish, but acceptable. I first machined a fixture hub, then bolted the rotor to the fixture. Trying to "turn" rotors you will bet "chatter". You need to run a VERY slow rpm (60 rpm's) and take very light .005" cuts. I also wraped the OD with a heavy duty rubber belt to minimise harmonics. My rotors were warped bad, they had .026" of runout. I got them to within .010" and they are fine now, no pulsating felt from the brake lever.