Bicycle Mechanics - Eccentric BB conversion

What has to be done to convert a BB to eccentric? Is it as simple as finding an eccentric BB whose outer cylinder has an O.D. that fits the frame? Or does the frame have to be cut and rewelded?
Thanks
T

You need a different bottom bracket shell. If your frame wasn't designed for an eccentric, it's probably a deal buster.

A while back, somebody posted a how-to build your own eccentric bottom bracket. It was a bit of a frankenstein but it could work. You'd have to do some searching on here and on google to find it.

A while back, somebody posted a how-to build your own eccentric bottom bracket. It was a bit of a frankenstein but it could work. Unless you're simultaneously swithching from Ashtabula to 3-piece I can't see how that's done.

Thanks for the answers.

Would it be feasible for a bike maker to offer a bike in both standard and eccentric BB versions, one with derailleur and the other internal hub with rear disk brake?

T

Well, If you use a crank with a 24mm spindle, there's this thing

http://www.trickstuff.de/index.php?p=d116en1

probably needs a halflink sometimes.

Would it be feasible for a bike maker to offer a bike in both standard and eccentric BB versions, one with derailleur and the other internal hub with rear disk brake?

Sure, but the market for the latter is so small that we're pretty much talking about bespoke stuff here.

Thanks for the answers.

Would it be feasible for a bike maker to offer a bike in both standard and eccentric BB versions, one with derailleur and the other internal hub with rear disk brake?

T

I think the Trek SOHO is that way.

search the word 'eccentric' in the single-speed forum and you will find a couple of threads related to eccentric crank options.

Well, If you use a crank with a 24mm spindle, there's this thing

http://www.trickstuff.de/index.php?p=d116en1

probably needs a halflink sometimes.

Thanks for the link!

Sure, but the market for the latter is so small that we're pretty much talking about bespoke stuff here.

Not necessarily. With an eccentric bottom bracket, and both v-brake and disc-brake tabs, and vertical dropouts, the bike can be configured so that it has either type of brake front and/or rear (or a roller brake) with derailer, internal hub, or single-speed. Now your bike can be positioned for multiple market segments.

If you ride in a mountainous area and are going down long hills on paved road, or if you commute in wet weather, you might prefer disc brakes. If your road is a bumpy one, you might want an internal hub because there's less slop in the chain compared to a derailer setup. With an EBB, no need for a chain-tensioner. Harsh conditions...the internal hub is sealed against the elements. Put the internal hub on a folding bike and you solve a commonly reported problem -- derailers getting damaged when the bike is being transported. Ride on smooth level roads, then you might want v-brakes and derailer.

The same bike frame satisfies multiple riders/conditions, within the parameters of its geometry.
Regards
T

There's a single speed 29'er at Nashbar I believe that comes in both "regular" and EBB forms for geared and SS use.

Thanks for the answers.

Would it be feasible for a bike maker to offer a bike in both standard and eccentric BB versions, one with derailleur and the other internal hub with rear disk brake?

T
Horizontal rear dropouts are a cheaper solution.

thats pretty sweet!

If horizontal dropouts are a 'cheaper' way to have the same frame be configured with either an internal hub or a cassette/derailer, they are also a lesser solution: repositioning the rear wheel in the dropout to tension the chain affects the brake alignment. If you were to use a chain tensioner as well, it hangs off the rear hub like a derailer and you sacrifice some of the benefits the rear hub brings; the tensioner can get bent during transport or when riding across an unmown meadow; the chain line has a little extra slop; the tensioner itself needs to be aligned.

Regards
T