calamarichris

Sorry, I know this question has probably come up at least a hundred times, but I'm too lazy and stupid to do a search.

Do you think it's possible to install an outboard bottom bracket (a Dura Ace external, 7900) on a eccentric BB shell (a Globe Live 3) ?

I love my belt-driven Globe Live 3, but the OEM cranks that came on it flare out and when I do any lively ride over 20 miles, it bugs my knees.

I've got a spare 7800 crankset & outboard bottom bracket. And Gates carbon belt drives recently released a five-pronged belt sprocket with a 130 BCD that will indeed mount on my 7800 crankset. And I feel pretty sure I can find or finesse spacers that will keep the belt in a straight enough line.
But are there any pitfalls to screwing an outboard bottom bracket onto a concentric bottom bracket shell that I'm unforseeing?

This is not my bike, but it's the closest Google could come up with right now:

calamarichris

P.S. I'm confident that both are English threading, so that's one less pitfall. Thanks!

FBinNY 

As long as the cam's threaded BB is an analog of a normal BB, then there's no reason that any BB made for a standard BSC shell won't fit. The BB only cares what it attaches to, is the thread and face, and doesn't care about what that part is in turn part of.

Before installing, though make sure the raised lip face on which your BB will sit, is properly faced parallel, as you would with a standard BB shell. Yours might already be faced, but may not since the lockrings you now have don't need a clean face.

fietsbob

Un weird tandem bike eccentric .. they typically were in front, to tension cross--over drive chains,
but work for single speeds and IGH chain tensioners too..

Andrew R Stewart 

The frustrating but work aroundable possible issue with an eccentric and external bearing BBs is that they might cover the peg holes in the eccentric (used to rotate the unit for chain tensioning). When i worked in a tandem shop about 5 years ago we had this problem a few times. Not a deal breaker but when your customer is spending 10K for a bike... As I mentioned there are other ways to grab the eccentric. Andy.

Chris_W

There should be no problem installing the outboard bearings in the eccentric, we have the captain's cranks on our tandem setup like that. For us, it makes rotating the eccentric pretty straightforward because I can use an open-ended HTII installation tool to grab the bottom bracket even with the cranks installed and it's then super-easy to rotate the whole assembly to get the tension right.

calamarichris

Thanks very much fellows. I had a feeling the outboard BB would cover up the allen-key adjustent port, and was prepared for that. Have ordered the needed components and will report back with any problems or successes.

calamarichris

Sorry for the delayed response.
It worked beautifully, and the outboard bottom bracket does NOT impede access to the allenkey-adjuster of the eccentric shell.
The bike rides like a dream, and I can now pedal it all day long without knee pain. And not only that, the larger 50-tooth sprocket means I'm not spinning-out on the flats as much.
Peace & safe riding!






So if anyone ever asks if it'll work, tell 'em "yes."