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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 02-26-14, 08:49 AM   #26
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Originally Posted by hamachi View Post
Using a hacksaw looks like the only way to open up a gap between the pinch bolt posts on my bottom bracket shell.
Use a Dremel tool with a cut-off wheel like the number 409 (hard), apply gentle pressure with the side of the wheel. Be careful, too much pressure will shatter the wheel. Eye protection is a must. You will typically go through several wheels on a job like this, which is not a big deal. But this process will get it done without so much elbow grease.

Originally Posted by hamachi View Post
I got my hands on a Shimano spindle that looked ideal because its bearing distance was halfway between the two Specialized spindles, but I couldn't use it because the metal ball bearing clips of my crankset would rub directly against the Shimano spindle.
Use loose ball bearings instead of the cage. Loose balls provide a better bearing surface anyway, since there will be more of them than the number of balls in the cage. Use grease to stick the balls in place for assembly.
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Old 02-26-14, 01:47 PM   #27
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Originally Posted by hamachi View Post
Thank you for the suggestions. I have attached a close-up photo of the offending bottom bracket shell. The stuff that appears to be in the gap is just grease that was squeezed out.

I'm thinking that the bosses are deformed, but not too much because the bolts still thread into the bosses pretty easily. I like the idea of filing off a little material so there's still a gap when tight.

Does anyone know the recommended torque for the bolts on the bottom bracket shell? Is there a good reference book for tandem bike repair? My Park Tool Big Blue Book has an appendix with recommended torque values for various bolts on bikes, but it doesn't have any tandem-specific information.

This picture tells a lot... the fundamental problem you have here getting the eccentric to tighten up is that the slot does not go all the way across the frame. See those round holes at the end of the slots? That is a standard crack stop and the intent is that only the very outside of the tube clamps. This means that the bolts are fighting against that solid center section and creating a conical shape of the tube as they pull the slots closed. It also means they are doomed to an angular change as the gap closes up. The wider you make that gap the more pronounced that angular change will be. I would focus on other methods of locking the eccentric from rotation if that is a real problem.

Thus I have to ask: you observed that there were no gaps when you took things apart but did you actually have any problem with the eccentric rotating? That was not mentioned and if it was not rotating by itself then it is not broken and does not need fixing.

If you really need to cut those slots wider... or cut down hardened steel bearing cups... you may want to check into a 4" angle grinder. Fairly inexpensive and, if you can hold the bearing cup in place, it WILL cut them down.
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Old 02-26-14, 05:26 PM   #28
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you might want to look into an eccentric, the the Bushnell, that locks with its own cams instead of pinch bolts or set screws
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