Wheels Manufacturing's Eccentric bottom bracket was originally designed to adjust chain tension on single-speeds. An added benefit is that it’s also a neat way to tweak your geometry.
Wheels Manufacturing’s Eccentric bottom bracket uses a two-piece design that lets you clock the BB within the frame. Because the sealed bearings are offset by 7mm from the BB centre, rotating it in the frame changes its position and lets you tweak the geometry of a bike. You can use it to drop your current BB height by as much a 7mm, or reduce the effective chainstay length by the same amount. Alternatively, clock the BB anywhere in between for a combination of both adjustments.
Granted, changing the effective chainstay length by 7mm will not make a massive difference to the handling of a bike, but a 7mm drop in BB height isn’t to be sniffed at. And, unlike using offset shock hardware to change the BB height, with an eccentric BB you won’t run into clearance issues when the suspension bottoms out. There’s no knock-on effect on the head angle either. Two bikes that would instantly benefit from the extra BB drop that the Wheels Manufacturing Eccentric BB affords are the Cannondale Jekyll and Specialized Enduro 29.
Available to fit PF30 and BB30 frames, with shell widths from 68mm to 73mm, the Wheels Manufacturing Eccentric BBs comes in both Shimano and SRAM/Truvativ GXP configurations. Unfortunately they are not compatible with 30mm spindles, so before you rush out and drop £99 on a new BB double-check your chainset configuration. If it fits, you are onto a winner as the Enduro bearings used come with a two-year warranty. It’s available from Madison in the UK, find it here on its website.