Winfried

Hello,

I have a bike powered by a Gates belt-drive and a Shimano Alfine 11. It also has an eccentric bottom bracket to adjust the tension on the belt drive, and a SRAM GXP bottom bracket.

The other day, just by following videos on Youtube since no other help was available, I tried replacing the old bottom bracket with a new one… and it looks like I ruined the threading on the drive side of the eccentric BB: I can hand-tighten it, but when tightening it further with a wrench, it loosens again, ie. I can never tighten if fully. It looks like I'll have to buy a new eccentric bottom bracket :-/

The issue: How to identify the brand + model of that eccentric BB without taking it out (I'll need to ride it to a workshop to fix it)? There's nothing written on the sides, short of L/R.

Also, while I wait for a new eccentric BB, I was thinking of applying some medium-strength threadlock in the hope that the drive-side bearing won't move. What do you think?

Thank you.

fietsbob

Ask your seller of that frame..

Solid piece of aluminum types are many .. held in place typically, by setscrews Underneath (unshown)

The ones like this .. Bushnell eccentric ebb chain tensioner

expand from within .. the shell does not contract* or have set setscrews digging into the aluminum .


*Tout Terrain compresses with bolts squeezing the circumference of a solid eccentric..

tout terrain

Winfried

I did, but they couldn't tell even when providing the bike's S/N.

FBinNY 

The eccentrics themselves are pretty generic. They're identified by the OD (ID of the shell in the frame) and the thread & width.

There aren't that many different ones, so feel free to shop by the basic dimensions.

Bezalel

The most generic ones are 68mm wide with a diameter of 54mm. Shops that specialize in tandems are your best source.

Slash5

Have you removed the BB that is stripped? The bearing cup is aluminum so I would expect it to strip before the bottom bracket.
I see you are in Europe - any chance the BB is Italian thread and you are trying to use English Bearings?

JohnDThompson 

I doubt that whoever manufactured your frame designed their own eccentric piece, but rather used an off-the-shelf part that should be available, e.g.:

Eccentrics available from Tandems East

TANDEM & SINGLE SPEED SHELLS :: BOTTOM BRACKETS :: Nova Cycles Supply Inc.

Other BB shells

Winfried

Thanks for the links.

I went ahead, cut the IGH cable hose + rear brake hydraulic hose because they stand in the way as they both run inside the frame on their way to the rear… and voilŕ (pictures attached).

It's just a cheap plastic EBB, which would explain how easily I managed to ruin the threading. But then, I'm good at breaking things.

As the pictures show, to make things more interesting, part of the inside is cut open to leave a bit of space for the two hoses to run through the EBB.

The bike assembler got back to me, and said the EBB is a Prime Aero, which appears to come from a manufacturer in Taiwan called Lagear. I doubt they'll reply to my email for infos on where to get a replacement; In the meantime, I'll look around and see if I can find one that fits.

Thank you.

fietsbob

well as plastic is not going to corrode, its not a bad choice ..

just be realistic when putting it back together , knowing the limits..



use anti sieze if the replacement is aluminum..




./.

Winfried

Yup, looks pretty hopeless to find a replacement in plastic, at 67g.

The lighter/cheaper option I found is indeed aluminum:
FSA BB 200 C Tretlager-Excenter 68 / 54,5 mm Innenlager online bestellen bei RADONLINE.de

Winfried

The replacement EBB just got in, and it fits right.

However, like the other replacements I found on the Net at an affordable price, after sliding the EBB in place, it has no opening at the bottom to let me reach the two housings (derailleur + hydraulic brake) coming from the handlebar inside the frame on their way to the rear. So the housings will have to be attached outside the frame with zip-ties.

But due to the shorter run, the new derailleur housing is too long, even after cutting it to the exact same length as the original.

Generally speaking, what is the correct way to determine how long a housing should be? I assume it should be as straight as possible, avoiding sharp turns.

Thank you.

Retro Grouch 

I'd check with "Tandems East" or "Tandems Ltd." I've had experience with both and I think that they are both good people. They'll have extensive experience with eccentric BBs and be able to give you helpful advice.