Tandem Cycling - More Summer Maintenance

I've got some dents in my eccentric. Sheldon Brown makes a reference to them with this type of eccentric. As long as I can adjust the timing chain adequately, should I not be concerned?

Also, the captain's bottom bracket (or whatever it's called) has a very slight hitch in it (I have to hunt for it when turning with my fingers). The stoker's bottom bracket isn't quite grinding, but is noticeably not smooth when I turn it with my fingers (with the cranks off). Should I go ahead and replace both?

Tandeming is not a sport for the light of wallet.

Tandeming is not a sport for the light of wallet.
So true. :cry:

As long as I can adjust the timing chain adequately, should I not be concerned?

That's correct. You can knock down some of the ridges with a flat file or emory paper if you're so inclined, but that's about all you can do to clean up the 'divots' from the grub screws.


Should I go ahead and replace both?

From Park's Website (http://www.parktool.com/repair/readhowto.asp?id=94):


There is a fairly simple test to determine if the bottom bracket bearing is worn out. Shift the chain to the inner most rear sprockets front and rear. Drop the chain off the smallest front ring, and arrange it so it will not strike the chainrings. Spin the crank while holding the bike with one hand. If you feel an obvious rumbling or grinding feeling, the bearing are wore out and the unit should be replaced. Very worn bottom brackets will actually make a grinding noise.

On the basis of what you've described... and the track record for the extra long-axle BB's used by Santana -- I would recommend you start the search for replacements. Depending on which one's you have, they're not always easy to come by.

On the basis of what you've described... and the track record for the extra long-axle BB's used by Santana -- I would recommend you start the search for replacements. Depending on which one's you have, they're not always easy to come by.

Thanks as usual, TandemGeek. I'm pretty sure I have the "standard" 73x129 splined octalink. Is there any source for these other than the big tandem stores?

You might look at the end of the grub screw and soften the edges of the
ring that is denting the eccentric housing. Be somewhat prudent in the
amount of torque applied to these. The Burley we started with had threaded
bump outs in the BB shell in which the grub screws fit and a problem with
a loosening eccentric resulted in a bit of ovalizing of the BB shell as the
grub screw lifted the shell away from the eccentric. Maybe 30-40 thousandths
gap developed.

Is there any source for these other than the big tandem stores?

I think, as Mark implied, that you will find that Octalink triple bottom brackets (needed for most Shimano 9 speed cassette equipped tandems) are getting as scarce as hen's teeth. I searched the big internet dealers 9 months ago and found nothing but a few Italian threaded models. The tandem dealers had some at that time but a friend shopping the major tandem dealers a couple of months ago came up dry. He was looking for Ultegra but managed to find someone with a few 105's in stock.

My suggestion is to check with a local bike shop to see if there is anything available in their network or check for NOS on eBay. Since Shimano has obviously seen fit to drop its manufacturing of compatable parts, it means that those without replacement parts will be forced to replace entire drivetrains, and that will be expensive.

Thanks Shimano! NOT! :mad:

Maybe the real "Thanks" should go to Santana for using proprietary parts- Kinda like the marketing department driving the design. The 160 spacing seems to cause more problems than it solves- If it even solves any problems...