Shimano GRX 12 Speed Di2

• Posted on 21 May 2024
• By Woz
• 0

Here's a fresh look at the new Shimano GRX group

Shimano surprised quite a few people when they released their 12 speed GRX several months ago and it was available only in mechanical shifting.  Today they release the Di2 electronic, wireless shifting version under the moniker of RX825.  The new RX825 kit shares most of it's pieces with the current RX820 mechanical groupset, with the exception of the new levers and derailleurs. There is also the addition of a Limited Edition GRX pedal.   

The lever and hood shape continues to be the larger, flatter style that one expects with a Shimano gravel group and does retain the grippy non-slip lever texture from previous versions.  A change in angle to better match flared bars and provide a flatter transition to the hood.   Servo wave braking and of course wireless shifting are the main changes here.  

The 12 speed RX825 rear derailleur will come only in one variation, which is intended for a 2x setup using an 11-36 cassette.  Not to say that it can't be run 1x, but rather it will not feature a long cage rear derailleur to accommodate a cassette larger than 11-36.  Those who wish to run it 1x will either run it with the 11-36 or will need to consider something like the classified powershift system to increase the gear range.   Like all of the current Di2 groups the rear derailleur will feature the system brain.  It is a shadow plus design and direct mount compatible with an adjustable clutch.  Pulley wheels are 11/13 and are designed for a large cog of 34 or 36 teeth.    

The front derailleur is braze on mount only and intended to handle up to a 48t max chainring size with a chainline of 47mm for increased tire clearance.  

There is also a release of a Limited Edition GRX pedal which unfortunately was not available at the time we received the early release of the groupset.  No release date has been set yet for the pedal, but we do know that it is based on the XT M8100 body.  And will be called the 8100-UG (United in Gravel) 

A new firmware update released at the same time allows single button front shifts, which has been a sought after feature missing from previous versions of Di2.  

Components from the current 820 groupset that carry over

Ultegra level RT-CL800 Disc Rotors.

105 level HG710 Cassette, 11-36

XT level M8100 Chain

GRX level RX820 Crankset

GRX level RX820 disc brake calipers

And the current DN300 battery, SD300 wires and EC300 charger all continue to be the components for all current Di2 groupsets.