In order to accommodate broader range cassettes, Shimano has adopted a new freehub standard for gravel bikes. The freehub used is the MSR, Micro Spline Road. It supports 12 speed. This allows gravel bikes to use Shimano Micro Spline freehubs.
Micro Spline Road offers a larger gear ratio allowing the smallest cog to be 10t and the largest cog up to 51t. This can make a gravel setup more versatile. The use of Micro Spline is designed for 12 speed, making the jumps between the cassette cogs smaller, allowing for better cadence
About the New Shimano GRX
The popular Shimano GRX groupset for gravel bikes has become quite ubiquitous. Recently, Shimano has decided to increase the gear range to 12 speed. This is found on the GRX RX820 and GRX RX610 gravel bike groupsets. This closes the gap to the other two main groupset manufacturers, SRAM and Campagnolo.
The groupset is available in both 1x and 2x options. Each option is available in three different setups, a 1x for gravel racing (named Unbeatable), a 2x for all-round gravel riding (named Undroppable), and finally a wide range mullet gearing x1 mullet (named Unstoppable). The shifters are all mechanical rather than electronic di2. The brakes are all hydraulic.
In addition to the changes in gearing, the groupsets also have some new design features such as better shifter ergonomics for flared bars and increased surface area on the levers to reduce hand pain. In fact, Shimano has integrated tech from their fishing rods to accomplish this. This can be found in the surface of the shifters which offers increased grip in wet conditions, allowing increased safety and confidence.
1x drivetrains have 10-46t and 10-51t, 2x have 11-34t and 11-36t, before it was 1x with 11-42 falling short of SRAM’s low and high gears, before SRAM used 10-44 in the XPLR range, and also offered 10-50 and 10-52 MTB cassettes, the GRX groupsets share cassettes with Shimano’s MTB drivetrains, this differs from the 12 speed HG L2 freehub standard on road bike groupsets, microspline can fit a 10t cassette
Elitewheels’ MSR Freehub Option
For all of Elitewheels gravel wheels, including the Drive G45 CS, the Drive G45 SS, and the Marvel G35, there are three freehub options including Shimano HG, SRAM XDR, and the new Shimano MSR