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Choosing between a single chainring (1x) and a double chainring (2x) drivetrain for your gravel bike can feel overwhelming. However, by considering your riding style and the terrain you tackle, you can quickly identify which setup suits you best. This guide dives into the key advantages, terminology, and recommended SHIMANO GRX gearing configurations so you can make an informed choice.

 

Key Gearing Concepts

Before comparing 1x and 2x, let’s clarify three key terms:

  • Gear Ratio - The relationship between front chainrings and the rear cassette cog. Higher ratios yield harder gears and greater top speeds, while lower ratios offer easier climbing and higher torque.
  • Gear Steps - The incremental differences between adjacent gears on a cassette. Smaller steps let you fine-tune cadence, reducing big jumps in pedaling effort. On the other hand, larger gear steps let you adapt to bigger terrain changes with fewer shifts.
  • Gear Range - The span between your lowest and highest ratios. For example, an 11–36T cassette has a 327% range. Adding a second chainring expands that range further.

GRX 1x Gearing for Gravel

A 1x drivetrain is favored by riders looking for simplicity in their shift system. Shimano’s GRX 1x12-speed Di2 uses a 10–51T cassette paired with a single chainring (40T or 42T) for customizable range and step sizes.

 

SHIMANO 1x GRX gravel bike gearing
SHIMANO 1x GRX gravel bike gearing

Pros of 1x:

  • Intuitive shifting (no front derailleur)
  • Better mud and debris clearance
  • Lighter weight and reduced maintenance

 

Chainring Choices:

  • 42T – Higher speed on faster roads, best for racers and cyclocross riders transitioning to gravel.
  • 40T – Balanced climb and speed for rolling terrain and long gradual ascents or those who prefer a higher cadence when riding.
  • 38T – For maximizing low climbing gears, especially for those who live in mountainous terrain or carry camping gear on multi-day rides.

 

GRX 2x Gearing

A 2x drivetrain delivers the widest range and the smallest gear steps, perfect for riders who prioritize precise cadence control. GRX offers two chainring pairs (48/31T and 46/30T) that can be combined with SHIMANO 12-speed cassettes (11–30T, 11–34T, 11–36T).

SHIMANO GRX 2x Di2 gravel bike
SHIMANO GRX 2x Di2 gravel bike

Pros of 2x:

  • Tight gear steps for smoother cadence transitions
  • Broad overall range for varied terrain and conditions
  • Versatility in headwinds, steep climbs, and fast flats

 

Chainring Combinations:

  • 48/31T – Suited to flat or rolling courses, racing, and sustained high speeds.
  • 46/30T – Ideal for steep climbs, and slower-paced endurance rides.

Cassette Options:

  • 11–30T (272% range) – Close-ratio cluster for rapid speed changes.
  • 11–34T (309%) – Balance between range and step size.
  • 11–36T (327%) – Lowest gears for the steepest climbs.
Shimano GRX RX827 1x GRX gravel groupset
Shimano GRX RX827 1x GRX gravel groupset

Comparing Cadence and Speed

Now, let’s take a closer look at gear steps and see how a rider’s speed changes when shifting between gears on a 1x and 2x setup. 

 

For a 2x12-speed setup using GRX 48/31T chainrings and an 11-36T cassette, a rider pedaling at 100 RPM will travel at the following speeds when in the smallest three cogs on the cassette while in the big chainring:

 

  • 35.4 MPH – using the 11T cog
  • 31.1 MPH – using the 12T cog
  • 28.7 MPH – using the 13T cog

 

This equates to a total speed difference of 6.7 MPH between the top three gears of the GRX 2x drivetrain system.

SHIMANO GRX 1x Di2
SHIMANO GRX 1x Di2

For a 1x12-speed setup using GRX 42T chainring and an 11-51T cassette, a rider pedaling at 100 RPM will travel at the following speeds when in the smallest three cogs on the cassette:

 

  • 34.0 MPH – using the 10T cog
  • 28.4 MPH – using the 12T cog
  • 24.3 MPH – using the 14T cog

 

This equates to a total speed difference of 9.7 MPH between the top three gears of the GRX 1x drivetrain system. The bigger speed difference is due to the bigger steps between cog sizes (10T, 12T, 14T). This illustrates how 2x yields tighter spacing, while 1x offers broader jumps.

 

Recommended Setups by Riding Style

If all this math is making your head hurt, here are some tested and trusted gear combinations for different kinds of riders. Choose a proven configuration based on your goals, then fine-tune chainrings or cassettes as you dial in your ride.

SHIMANO GRX 1x vs 2x comparision chart
SHIMANO GRX 1x vs 2x comparision chart
Shimano GRX Di2 1x
Shimano GRX Di2 1x

Whether you relish the elegant simplicity of 1x or the nuanced control of 2x, Shimano’s GRX lineup has you covered. From high-speed racing to bikepacking expeditions, there’s a gearing solution that matches your terrain and riding style. Now, gear up, explore beyond the pavement, and enjoy every turn of the crank, no matter how many chainrings you choose.

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