Bad rotor: question? - Wrist Twisters
 
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post #1 of 5 Old 06-16-2011, 07:51 PM Thread Starter
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Bad rotor: question?

I'm doing the 6 spoke wheel conversion, I'm pretty much ready. Got the wheels powdered, new bearings and seals, got some spacers machined...

Only one problem, I bought some used rotors from the "internet" and one of
them happens to be warped. .050" with a dial indicator.

Just wondering how much of a pulse I would get from .05"?
Would it be safe to ride until I got a new set?

I was planning on installing them this week-end, I might have to wait
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post #2 of 5 Old 06-16-2011, 08:51 PM
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You will feel 50 thou.
50 is beyond pulse.
That is into major piston displacement territory.
You might get a big surprise on the first pull of the lever, and I don't mean just a pulse.

You may also be able to do some straightening of it.
Eons ago a good friend of mine had a duff rotor, CB750 1971.
He pounded it out with a brass hammer. (I can't remember what it was out, but it was in the problem zone, that is for sure, but less than 50 if I remember correctly - it has been a while)
That rotor went on a production racer and was a podium bike, need I say more as to what is possible with the skillful use of a hammer ?
Those old discs were really thick, and it took some serious work.

Your rotor is thinner and on floating pins.
Depending on the gradient of the runout, you may be able to do a decent job.
How you support it, and where, will have a big effect, including whether you make it worse or better.

Also.
Check you floating pins and make sure that those are not the problem, or part of the problem.

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post #3 of 5 Old 06-16-2011, 09:53 PM Thread Starter
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The bad area is within 90 degrees on the rotor. Probably easier to fix...
If it's been done before I will have to try it.

Thanks

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post #4 of 5 Old 06-17-2011, 01:18 PM
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Quote:
Originally Posted by Mr T81 View Post
The bad area is within 90 degrees on the rotor. Probably easier to fix...
If it's been done before I will have to try it.

Thanks
I just realized something.
A rotor dial check is not complete if one only dials off a rotor face.
Maybe you did other checks and didn't mention them.
Just in case you didn't, here's a bit more to ponder before pounding.
When you dial off the rotor surface, you are reading a cumulative runout.
You want to be sure where the runout exists before deciding upon any needed corrective action.
The rotor carrier should also be dialled. Try getting a reading on the outside and inside faces, seeing as that's were the spring loaded floating button ends face up on. You should be able to get a good dial path just inboard of the buttons.
Also check the hub face that the carrier nests against the wheel with.
Also check the wheel's hub face where the carrier nests against.

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post #5 of 5 Old 06-17-2011, 03:53 PM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
I just realized something.
A rotor dial check is not complete if one only dials off a rotor face.
Maybe you did other checks and didn't mention them.
Just in case you didn't, here's a bit more to ponder before pounding.
When you dial off the rotor surface, you are reading a cumulative runout.
You want to be sure where the runout exists before deciding upon any needed corrective action.
The rotor carrier should also be dialled. Try getting a reading on the outside and inside faces, seeing as that's were the spring loaded floating button ends face up on. You should be able to get a good dial path just inboard of the buttons.
Also check the hub face that the carrier nests against the wheel with.
Also check the wheel's hub face where the carrier nests against.
I was going to dial the rotor carrier before trying to straighten it
but I never thought about dialing the wheel hub, good call...

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