Bottom Brackets

Bottom brackets may be the most overlooked part of the bike. While upgrading a bottom bracket doesn't provide the flash of new carbon parts or a fast new wheelset, it can be one of the most effective in increasing your performance on the bike.

Bottom brackets are the bearing cartridges attached to your crankset. As one might imagine, cranksets take a great deal of abuse. They experience more torque than any part of the bike. Every acceleration made on the bike is caused by creating a great deal of stress on the bottom bracket. Due to this stress, a stiff, durable, smooth running bottom bracket is imperative in maintaining an efficient bike.

Over the past several years there have been many attempts to standardize bottom brackets between brands. No bottom bracket type ever really took hold and became a bona fide standard, but most bottom brackets fit into one of these categories.

Square Taper Bottom Brackets

Square taper bottom brackets are the most intuitive bottom bracket design. The crank snuggly fits onto the tapered, squared bottom bracket axle. The four-sided axle leaves little room for adjustment or variation and creates a secure, hassle-free contact point for your crank arms. In the old days, square taper was referred to as "cotterless". While square taper bottom brackets are simple, they are not universally compatible. The size and angle of the taper differs from brand to brand.

Campagnolo is the most notable brand to stick with a square taper design until very recently. Every Campy crank made until 2007 utilized a square taper design, even the ultra high-end Record group. In 2007 Campy introduced their Ultra-Torque outboard bearing bottom bracket system.

Octalink

Shimano developed Octalink in the mid-1990's as their exclusive bottom bracket/crank design. As Octalink is proprietary to Shimano, no other brands manufacture Octalink-compatible parts. Octalink features an 8-spline axle which connects to the crank arms, rather than a square tapered axle.

Octalink was replaced in Shimano's Dura-Ace level components with the outboard based Hollowtech system in 2004. The Hollowtech system has now trickled down through Shimano's road and MTB component lines. Shimano's Track cranks are the only Octalink-compatible cranks manufactured today.

ISIS Bottom Brackets

ISIS bottom brackets were developed in the mid-1990's as a response to Shimano's Octalink system. While Shimano patented Octalink, ISIS was put in the public domain so that anybody could make parts for the system, it became very popular. ISIS utilizes a 10-spline axle. FSA Platinum Pro MegaQuad ISIS Bottom Bracket is an excellent ISIS bottom bracket.

The primary drawback of ISIS and Octalink bottom brackets is bearing durability. Due to the fairly wide (and stiffer) axle, ISIS systems used smaller bearings which wear relatively quickly. ISIS bottom brackets are still fairly common, but popularity is decreasing as outboard bearing set-ups become more common. Square taper bottom brackets can be made with larger, more durable bearings which would require a narrower, less stiff axle.

Outboard Bearing Bottom Brackets

In 2004, Shimano introduced their Hollowtech crank system. Hollowtech cranks were the first mass production crankset to feature a bottom bracket with outboard bearings. It has since trickled down to their entire road and MTB line, Dura-Ace track cranks are currently the only Octalink products still in production. The outboard bearing system is one of the few bicycle innovations that provided an improvement on all fronts, with little increase in cost. Outboard bearing bottom brackets are stiffer, lighter, more durable and due to the simplification of the bottom bracket itself, they are not much more expensive than the standard ISIS, Octalink or square taper bottom brackets they replaced.

Outboard bearing bottom brackets are simply cups installed in the bottom bracket with bearings held outside of the frame. Essentially, this allows for a larger bottom bracket mechanism. Larger bearings provide increased durability, larger axles can be made hollow to save weight, outboard bearings provide a wider platform, increasing stiffness.

Due to these advantages, outboard bottom bracket systems are quickly becoming standard. In 2007 Campagnolo introduced their Ultra-Torque outboard bearing system. SRAM's Red, Force and Rival are all equipped with outboard bottom brackets. As always, there are slight variations from brand to brand, it's best to run a crankset with the manufacturer's recommended bottom bracket.

FSA is a relative newcomer to the component game, but has become very visible at cycling's highest levels. Their Mega Exo bottom bracket system has become very popular.

Ceramic Bottom Brackets

The next bottom bracket innovation has to do with the bearings inside the bottom bracket. Research has found that ceramic bearings are more efficient and more durable than their steel counterparts. Ceramic bearings have 5-10 times the durability of steel bearings, are 10 times rounder, 20% stiffer and weigh 40% less than steel.

FSA Ceramic Mega Exo Bottom Bracket will improve the efficiency of your FSA MegaExo crankset. The SRAM Red Group Set is the first groupset equipped with ceramic bearings in the bottom bracket, derailleur pulleys and even the brake pivots.

Bottom bracket overhauls and replacement should only be attempted by an experienced mechanic. Improperly installing a bottom bracket can easily ruin a frame. New frames often need to be "faced" before bottom bracket installation, this should only be done by an experienced mechanic with the proper tools. For any questions regarding bottom bracket selection and compatibility, please contact us at sales@westernbikeworks.com or 1-800-651-4050.