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square crank - engaugment length on shaft

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square crank - engaugment length on shaft

Old 03-07-11, 08:44 PM
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square crank - engaugment length on shaft

what is the correct length of crank arm to shaft engaugment, or how far should the crank arm push on to the bottom bracket shaft. I've push it on and it is 5mm away from where the washer sits (end of shaft). Its engaugment, alloy contact area to shaft is about 12mm. Does this seem OK. It is a mismatch of campag cranks and different shaft? old Scapin frame. I have noticed some cranks push onto about 2mm from shaft end? any thoughts, Cheers Ben
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Old 03-07-11, 09:42 PM
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Ideal engagement has the spindle ending roughly 2mm sub-flush. You have less than ideal though you didn't say whether that's after you torqued it on. 12mm engagement is reasonable though another 2-3 would be nice.

This isn't a digital pass/fail concept, more engagement is better, less is worse. Whether you have enough depends on things like what you weigh, and your riding style. For a 150# spinner, I'd say no problem. For a 200# masher, it might be dicey.
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Old 03-07-11, 09:49 PM
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Sounds like you're pushing ISO cranks onto a JIS spindle.

While the engagement is fine, my crystal ball sees you sorting out loose crank arms ... over and over. Just get a ISO bb.
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