Shimano Dura Ace BB86 Bottom Bracket

The 86mm bottom bracket is a relatively new, reasonably beefier BB standard that allows frame designers a little more leeway to play around with seat tube, downtube, and chainstay designs. The new, larger shell requires a larger bracket, obviously, and Shimano designed the Dura Ace BB86 Bottom Bracket to quite literally fill the gap. While it's a little larger than traditional BBs, the BB86 has the same design as Shimano's other Dura Ace brackets, with steel cartridge bearings packed inside composite cups and plastic o rings and dust shields to keep everything running smoothly. The 86 is also compatible with Shimano HollowTech cranks, so you can keep your old crankset even if you're getting a new frame.