Of course, there’s a difference between what’s recommended and what actually works. Due to a mix-up, our test bike arrived with a GRX 2x RX810 crankset, front derailleur and front and rear shifters, but with a 1x RX812 rear derailleur. It did the job without complaint or issue, and I likely wouldn’t have noticed until I asked Shimano’s Nick Legan why his bike had oversized pulleys while mine did not. Legan diligently followed up, and discovered by mistake I was supplied the wrong derailleur for the 48/31 and 11-34 drivetrain.

In a day I had the proper unit.I swapped the RX812 derailleur out for the RX810, made a few adjustments and hit the dirt again. The shifting was crisper across the two chain rings as the upper pulley of the RX800 derailleur remained consistently closer to each cog across the cassette. However, I’m thankful for the mixup, as it revealed the effectiveness of the Shimano clutch, as the 1x derailleur handled shifting duties without a chain drop, even though the drivetrain was 9 teeth over the derailleur’s stated capacity.

Similarly, the 2x derailleur can handle duty with larger-than-stated rear cogs with some aggressive B-screw adjustment. We’ve done the same with the RX800 and RX805 derailleurs. Shifting may not be optimal, but it’s certainly possible.

Shimano GRX boasts gearing versatility, but it’s actually even more than the specs indicate.