If you've got a gravity bike with stays 150mm apart, your selection of hubs that fit is a bit more limited, but the options are growing. Thankfully, Shimano has continued to build a 150mm over lock nut width hub as part of their new Saint group. It is known as the Saint M815 rear hub.

The thing everyone will appreciate first about the Shimano FH-M815 Rear Hubis that Shimano knocked 100g off the weight of the hub compared with the previous Saint. They've gone to a new micro-ratchet freehub design, with 36 clicks in a 360-degree turn. This cuts the engagement time down by half. The freehub will engage within10 degrees. No more of that perilous wait between starting pedaling and wheel movement at slow speed. As is now typical with Shimano, you still get splines for Centerlock rotors, angular contact bearings, and a completely new design for the seals, using labyrinth and lip seals to improve the hub's ability to keep dirt out by 400%.

The Shimano Saint FH-M815 M810 rear hub comes drilled for 32 or 36 spokes. The cassette body accepts eight- and nine-speed cassettes. The hollow axle fixes to the dropouts with a nut-and-bolt design that has the bolt end on one side and a nut on the other. The hub is designed to work with Shimano Centerlock compatible disc rotors. The hub comes with a cover that can go over the rotor splines. The hub turns on angular contact bearings. The bearings run on Cubic Boron Nitride cone and cup races. The hub shell is anodized aluminum. The over lock nut distance is 150mm. The perimeter circle diameter is 44mm on the left and 45mm on the right. The flange diameter is 52.8mmon the left and 53.8mm on the right. The flange distance is 72.4mm. The dish is 6.6. Black. 372g. MSRP is $210.