Shimano has expanded the options available in its GRX RX810 12-speed gravel groupset, offering more choices to configure the groupset to meet your requirements.
First up, it will now sell 160mm and 165mm crank-arm lengths alongside the existing 170mm, 172.5mm and 175mm cranks.
When Simon von Bromley asked Shimano why crank arms are the length they are, as part of his detailed feature on the best crank length for cycling, the reply was: “170-175mm cranks provide an optimal balance between rotational inertia [the torque required to turn the crank], rotational speed [i.e. cadence – shorter cranks have to be spun faster to achieve the same power output and vice versa], frame design [longer cranks require a higher bottom bracket to achieve the same pedalling clearance] and biometric issues [longer cranks place greater demands on joints and muscles as the turning circle is larger]”.
But there’s a general trend for shorter cranks, with Jonas Vingegaard spotted experimenting with cranks as short as 150mm.
Shimano states shorter cranks can enable riders to pedal more efficiently and at higher cadences, while reducing joint strain. It singles them out as an advantage in particular for long gravel rides and races.
In addition, they’re likely to be a better choice for shorter riders and may improve ground clearance a little on more technical terrain.
As tends to be the case, SRAM got there first, though. Its Red XPLR crankset and power meter are available with six crank-arm lengths, starting with 160mm and 165mm, and heading up in 2.5mm increments to 175mm. Force XPLR and Rival XPLR omit the 167.5mm length.
Larger chainrings for gravel racers
The existing GRX RX800 series offers 40- and 42-tooth chainrings, which might be a little too small for gravel racing and those who ride predominantly in flatter places.
So Shimano has added new 44-tooth and 46-tooth chainring options to enable faster riders to spin more efficiently. It claims a bonus of lower friction from less chain articulation. That’s not likely to be so significant at the crankset, but also tends to place the chain more towards the middle of the cassette, where there are more teeth engaged, and the effect of lower chain-link articulation and a straighter chainline are more pronounced.
You can swap the new 44t and 46t chainrings into the current GRX 800 series and 600 series cranks.
Again, SRAM got there first. Its Red Thread Mount 1x chainrings come in 38, 40, 42, 44 and 46-tooth sizes.
