Eccentric bottom brackets (EBB) have been used for years on single speed bikes to make the job of tensioning the chain easier than using horizontal rear dropouts. This solution allows the use of vertical dropouts in the frame and a quick release skewer to secure the rear wheel – a feature that anyone who has been miles away from home with a flat, but no wrench to remove the wheel would appreciate. With the advent of the oversized PressFit-30 (PF30) bottom bracket shell used in all types of bikes to provide a stiffer, more efficient power transfer from the pedal to the rear wheel has lead to an unexpected aftermarket part for those wanting a single speed bike – the Eccentric 46 Bottom Bracket from Problem Solvers of Bloomington, Minnesota.
The Eccentric 46 fits into 46mm diameter bottom bracket shells and acts as a EBB for any PF30 with matching specifications. The E46 accepts 24mm crank spindles, the same size as found in use with Shimano Hollowtech II, Race Face X-Type or FSA MegaExo cranksets. Once the Eccentric 46 Bottom Bracket is installed, you have 16mm of fore-to-aft adjustment to properly tension your chain. Most eccentric bottom bracket shells have a diameter of 54 to 60.5mm which allows approximately 20mm of fore-to-aft chain adjustment so the Eccentric 46 provides only slightly less adjustment.
Once you have verified that the Eccentric 46 Bottom Bracket will fit your PF30 bottom bracket shell, there is one of main concern for those with a full suspension bike. You will also need to make sure that the full suspension frame does not increase the distance from the center of the bottom bracket spindle to the center of the rear hub axle when the rear suspension is compressed. If the distance changes, you will snap your chain at a minimum and possible cause more severe damage.
The Eccentric 46 Bottom Bracket details:
– Fits frames with 46mm diameter BB shells
– Spacers included for 68mm road or 73mm mountain setups
– Accepts 24mm spindle cranksÂ-Hollowtech II, X-Type, MegaExo
– GXP spacer kit sold separately
– Approximate MSRP $160
Problem Solvers is owned by one of the largest bicycle parts distributor, Quality Bicycle Products (QBP). Most bicycle shops order from QBP, so you should have no problem ordering your own Eccentric 46 Bottom Bracket. If you like the idea of being able to buy a bike with gears that could cleanly be turned into a single speed, then make sure to buy your next bike with a PF30 bottom bracket shell and have them order you up QBP part number CR0098.