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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 10-05-09, 08:36 AM   #1
Bradford
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Frozen Eccentric

Help!

The eccentric on our captain bottom bracket seems to be frozen. The bike is a 2006 Co-Mo Speedster. I have adjusted the eccentric, or had it done, twice in about 6,000 miles. The chain is slack and I notice that the eccentric appears to have slipped, because the last time I adjusted it the eccentric was pretty well maxed out on the long side. Now it is not.

Is there anything to do short of taking it to the LBO? Should I use WD-40 and wait? Should I apply heat?

Thank you for any help you can offer.

Brad Wyman
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Old 10-05-09, 09:11 AM   #2
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Is this what your eccentric looks like?



If it does, have you loosened all four set screws / two per side?
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Old 10-05-09, 12:23 PM   #3
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Yes and yes.
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Old 10-05-09, 02:34 PM   #4
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If you haven't already, take out all the screws completely, give it a light tap and then see if it moves.

.
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Old 10-05-09, 03:00 PM   #5
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Or even a heavy tap. I remove mine at least once a year and give it a good greasing. Heat shouldn't be necessary.
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Old 10-05-09, 03:01 PM   #6
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Quote:
Originally Posted by Bradford View Post
Yes and yes.
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Originally Posted by Stray8 View Post
If you haven't already, take out all the screws completely, give it a light tap and then see if it moves.
Sort of...

I'd almost recommend having it serviced at this point, which would entail removing at least the right side crank so that the eccentric assembly (with the bottom bracket & left side crank / timing ring still attached) could be removed from the frame so the eccentric and eccentric shell can be cleaned and coated with some waterproof grease before re-assembly.

I mention this only because if it was me I'd probably re-tighten the 4-screws and then remove the crank arm before I knocked the eccentric loose: it just makes it easier to remove the crank arms if the eccentric is secured in place.

After having the right side crank arm off I'd once again loosen the four screws and tap on the right end of the crank spindle with a plastic mallet to break things free. My guess is, you've got a lot of grime that's been trapped in the two moving parts that fix the eccentric in place. Once the eccentric is loose, you can slide it out of the frame from the left side and then clean everything out with some WD-40 followed by some compressed air.

Now, you could take the easy way out and just knock it loose, then use a pin-spanner to rotate the eccentric so that the slack was take up from your sync chain. I'm just not a fan of spraying solvents into places if the crud you're trying to unlock doesn't get removed.

This all takes more time to describe than it does to do if you have the tools needed for the job, and even those are pretty straight forward for this type of maintenance.
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Old 10-08-09, 06:31 AM   #7
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Thank you all for the suggestions. I was reluctant to "tap" the BB lest I cause some damage. I'll get back at it and see how I make out. As to removing the set screws entirely, I don't think I can do that because the outboard bearing overlaps them.

Again, thank you for your help.

Brad
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Old 10-12-09, 08:18 PM   #8
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Thank you all who responded to my call for help. With your advice I have successfully removed, cleaned, replaced and adjusted the eccentric BB.

Regards,

Brad
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Old 10-13-09, 11:21 AM   #9
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Great! Once you get the shims un-stuck, it should be as easy as cake.

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