Disc brake resurfacing/turning

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Feb 5, 2015
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Maybe someone out the can help me, I have a Harley RK that has a warped front disc. I thought no problem, take it to the dealer and they can turn it and flatten it out, right? No dice, they won't even do that work of fear or legal trouble. I called an independent Harley shop and no go there either. So was I mistaken that this type of work is common? If I need to replace the rotor I will, I was just hoping to find a cheaper alternative having it turned. And if I do have to spend money on a new rotor , I may want to replace them both with aftermarket discs (if there's a performance improvement) rather than Harley OEM at $150 per disc. Any info is appreciated.
 
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I would not expect that you can find anyone to turn it - for legal and safety reasons. if you remove material from the rotor, it will heat up even faster. I would replace the front rotor (check EBC) and leave the rear one alone. most of your braking is done by the front brake.
 
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Usually you can find a machine shop that will turn rotors. But the question is, what's the minimum thickness that you need and will it meet that after turning it?
 

SR5

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My car rotors are 25mm thick when new, and their service limit is 22mm, at which they need replacing. Minimum thickness is the big issue. You need to know this.
 
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Motorcycle rotors are usually stainless, and doesn't machine as well as ugly cast iron. And they are normally at minimum thickness by the time they need a resurface.
 
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Sorry to go against the grain here, but a guy over here in the UK has just had this work done on his ZX6R to remove some warpage and he's someone I would turn to for advice. As long as the disc is within the service limits after turning, it should be ok. not me mind, i'd buy the new rotor, turning is sort of like patching up a parachute. atb
 
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Proper machining can result in a rotor that is better than new. The set I have for track use is always machined so they are nearly perfect. The set for street use is not nearly as critical. Out of the box rotors can be anywhere from great to terrible. Sloppy machining is something you must be aware of. And most every rotor has a minimum thickness spec stamped right on it somewhere...
 
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I did some on my flywheel grinder. The noise was awful and the labor involved was way more than new rotors. They looked and stopped well but it was just too expensive to be practical. I won't go into the set up problems, a real pain in the neck. Smoky
 
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In the early nineties I sent a warped disc from a CBR 1000 Hurricane to Mares Cycle in Illinois. They surface ground the disc. They also advertised disc straightening. The disc worked fine when I refitted it. I would hesitate to use a common disc cutting tool on a thin drilled motorcycle disc however.
 
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We tried to see if we could do it on our AMMCO machine back in 2010 and it did not work out well whatsoever. The bike was a Harley Dyna and the owner asked us to try and being curious we did. As others have said, bikes use different materials for their discs and the nature of the design makes it hard as heck to do on an automotive resurfacer.
 
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The difference between someone who can turn a rotor and someone who can't , is one is a mechanic and the other, a parts changer. A mechanic earns his pay, the other guesses and throws parts at a problem hoping it fixes something.,,,
 
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