Importantly, none of these designs would go on to become a standard for the industry and to this day manufacturers remain free to adopt (or invent) any bottom bracket design that satisfies their needs. The rise of composite frames encouraged further development of threadless bottom brackets, and the designs - PF30, BB86, BB90, OSBB, BBright, BB386EVO - that emerged over the next ten years were a mixture of open and proprietary inventions. Rather than patent and protect the design, the company offered it openly to all frame manufacturers to encourage uptake by the industry. The oversized threadless shell was designed around a 30mm crank axle with bearings that were pressed directly into the frame. The first of the new wave of bottom bracket designs broke in 2000 when Cannondale unveiled BB30 at the Tour de France. BB386 was developed by expanding the width of PF30 to match that of BB86. PF30 is a direct descendant of BB30 with a slightly larger shell diameter so that cups could be used with the same bearings. At face value, Trek’s BB90 may look a lot like BB86 but the internal diameter is a little smaller. BB86 was the first threadless shell that was specifically developed to suit carbon fibre frames. Cannondale has remained true to BB30 since it introduced the design in 2000. T47 is the newest threaded bottom bracket design that is well suited to 30mm crank axles, yet it can be easily adapted to smaller diameters like Campagnolo’s 25mm Ultra-Torque axle. BSA-threaded shells are a common sight for frames made from metal, be it steel, alloy, or titanium. Italian-made frames often feature Italian-threaded bottom bracket shells, such as this classic Concorde Squadra from the ’90s with Cinelli’s iconic spoiler shell.
From that point on, the weight, stiffness and reliability of cranks improved, plus, they were easier to install and service. Shimano’s Hollowtech II cranks, unveiled in 2003, essentially ushered in the current era of crank design by integrating the axle into the design of the crank.
Meanwhile, Magic Motorcycle developed external bottom bracket bearings so that an even larger axle could be used for its ground-breaking cranks. In 1992, Shimano started bringing sealed bottom bracket bearings to the masses with the introduction of its innovative cartridge system, and then came Octalink in 1996, a larger diameter crank axle with a new interface for the crank. Few riders ever seemed to complain about clicking or creaking from the bottom bracket, however the cranks were troublesome, sometimes creaking, or more often, coming loose on the square-taper axles that had dominated the industry for a couple of decades. Two things stand out from that time: first, servicing a bottom bracket was labour-intensive and second, there were rarely any complications when fitting a new crankset to a frame. The only other thing that varied was the length and offset of the crank axle. When I started working as a mechanic in the mid-90s, there were essentially two types of bottom brackets for road bikes, English- or Italian-threaded. In this post, Matt Wikstrom updates his original article from 2014 with a look at the range of bottom bracket and crank axle designs that are found on the market today and discusses the details that are important for matching one to the other. The once ubiquitous threaded bottom bracket shell has given way to larger threadless designs while the diameter of crank axles has also grown.īoth may have helped elevate the performance of contemporary road bikes but consumers have been left to contend with myriad options and some frustrating incompatibilities. A singles details/254826835229/specialized-pro-fact-carbon-crankset-osbb-170mm-52-36-11-speed-black-silver_crankset-crank_crank-speed.html inwind it verapsandra3874ĭetails/254826835229/specialized-pro-fact-carbon-crankset-osbb-170mm-52-36-11-speed-black-silver_crankset-crank_crank-speed.html 6018ĭetails/254826835229/specialized-pro-fact-carbon-crankset-osbb-170mm-52-36-11-speed-black-silver_crankset-crank_crank-speed.The evolution of road bikes may have provided cyclists with frames that are lighter, stiffer and more aerodynamic, but there has also been a substantial increase in the number of bottom bracket and crank axle designs.