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Doing the brakes on my gl1100. It put a dial indicator on the rotor and turned the wheel. I have some run out. How much is too much? Any way these rotors can be trued? I had a bike rotor that was totally flat cut on a flywheel grinder at a machine shop once. Not sure what with the offsetwhat can be done to these.
 

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my manual calls for a max run out of 0.3 mm ( 0.01 in ) any more and it says to replace it . page 14-8 honda manual . dont know about haveing them turned back true . but id go with a grind instead of a lath turn .
 

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I have read all the manuals, looked at this situation from time to time, not really sure what they mean. I do know if you put the dial indicator on the frame or fork and turn the wheel you would be getting a measurement from three places, the rotor, the wheel bearing and the actual wheel. So that may not be accurate.

I think you would have to take the rotor off and put it in a truing stand and test it that way. Too many other variables at play otherwise .

Kit
 

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I made a indicator bracket by welding a length of rod onto a vice-grips. It allows for more clamping options than does a magnetic base...on bikes where so much of them are aluminum. Just be sure to clamp over a folded shop rag, etc., to prevent marring from the jaws.

I put a couple of chalk marks on the rotor for reference points, and then recheck those spots for consistency. I also push-pull the wheel sideways to take note of bearings condition.

Also have been told by mechanics that I respected over the years...to NOT get the rotors perfectly true. Minimal "wobble" (.002" to .004" T.I.R.) will help to "slap" the pads off of the rotorsto promote free running/less dragwhen brakes are not applied. :waving:

I would be interested in further "experienced" discussion on the "wobble" theory...:baffled:
 

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True , thickness is important, but the action of the brakes should tell you something. If the pulsing of the brakes jerk you back and forth, they are ruined no matter how much meat is remaining.

It appears to me that the ventilated Aspencade front brake are more susceptable warpage.
 

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I've never turned a bike rotor, it's just as cheap to replace it
 

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Ghost, are you just measuring since you happen to be doing your brakes, or are you measuring since you know your rotors are warped and gives you the rotor shake when the brake is applied?

If you can not tell the rotors are warped from applied pressure, I do not really think I would be concerned.

Grinding a MC rotor is not really economical. Some machine folks may do you a favor, but if you really had to pay theman honest wagefor there time and set up, cost would be too high.Someone did post a rotor grind for about $50, that cheep IMO. Turning carrotors and drums at a local shop (~$6 - $8) is really one heck of a deal for customer satisfaction.

Fenderhead (Wobble): Need to go for zero. What is bad about MC rotors is that this wouldrequiretwo separate machine operations for both surfaces. So, a tolerance stack of not just TIR run out, but two reference plains. With two surfaces, the thickness can vary Min/Max MMC. The automatic car rotor machine makes the cut on both surface, but the machine holding fixture will maintain the parallel surfaces in relation to the rotating axis. And, you would not want any TIR on a replacement rotor for your car, right.

I have more of a wear problem with the rotor "dishing". Thinner in the middle than the outer or inner diameter. I donot having a good machinist available, and I am not willing to pay for justified machined work which actually I am a believer. Even aftermarket rotors are expensive, soI resort to buying used ebay rotor and hope for the best.
 

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My problem was a caliper siezed up. Blued up the right rotor. After taking apart and rebuildingf caliper when installed and turn the wheel you can hear it tap the rotor to shoes every revolution. Put a dial indicator on it and it has about .015 run out.
 

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I would replace the rotor. Good ones are on ebay all the time.
 

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Well I decided to get my own fixed. I was affraid to buy a used set and be in the same shape as the ones I have. Took them to my local NAPA. They machined them on a flywheel grinder. They look like new. And are perfectly straight. $41 ea. That sure beats the $200 ea price I found for replacements.
 

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Depends on how much meat is left to grind off. All the new rotors are pretty thin.

Get another rotor off ebay, but ask about how good that one is, and pray the guy knows or is telling the truth.
 

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Ghost, that is good to know.

If Napa will do them for $41, I am going to check my local Napa and other local parts stores that does flywheels. I have spare rotors, and I will still do the ebay thing. Grinding will now be another option for me. On cars,Ido complete brake jobs and pretty much always have therotorsturned regardless.
 

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Just for your own safety, on the rotor, near the center of the cast area you will find numbers that refer to minimum allowable thickness. test your rotor thickness to ensure they dont go below minimum. I had one lock on a car when my caliper cracked through the rotor which jerked the wheel & destroyed alot of parts when it did. On a bike, it could cause lock up.

That way when you begin riding, you will feel confident in your wing, not worried.
 

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Rotor is thick enough. If a machine shop is worth using they will check it and not turn or do any work to a part that is sub standard. Good point though.
 
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