Old 03-09-21, 10:42 PM
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Join Date: Apr 2005
Location: Northern CA
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Bikes: Cannondale tandems: '92 Road, '97 Mtn. Mongoose 10.9 Ti, Kelly Deluxe, Tommaso Chorus, Cdale MT2000, Schwinn Deluxe Cruiser, Torker Unicycle, among others.

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Originally Posted by sapporoguy View Post
I'm posting in case it helps anyone.
I wonder why the failure. Fatigue? Material failure? Over-torqueing by prior owner (not me!)?
In any case, thanks to Mel for the quick solution.
I'm not sure how the prior owner could have "over-torqued" it. Isn't it simply tightened every time you slam on the rear brake? That thing must get INCREDIBLY tight. And it seems to me no set screw would be able to counter the torque forces created by the rotor.

The incorporation of wrench flats on that donut appear to be its Achilles heel. Dumb to reduce the thickness on something that sees so much force. That sure looks to me to be the reason it cracked in two. Shoulda forgone the wrench flats and simply utilize the rotor bolts for removal. It would require some tooling, but that seems like a much better way in the long run. Or utilize titanium or another material with higher strength.
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