Join Date: Mar 2013
Bikes: Co-Motion Primera Co-Pilot, Trek Madone 3.1, Trek 7300, Electra Townie 21D
Originally Posted by hamachi
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.