Road chainrings

How to choose road bike chainrings

Changing chainrings alters the bike's behaviour without changing the rest of the drivetrain. Shimano, Stronglight, Rotor and SRAM offer double and single chainrings, in round and oval versions.

What BCD does my crankset have?

• Thebolt circle diameter (BCD) is the distance between the mounting holes: 110 mm on most current compact cranksets, 130 mm on older standards.
• Recent Shimano and SRAM cranksets use mounting systems with 4 asymmetric arms, specific to each brand.
• Measure or check your crankset reference before ordering: it determines the chainring, not the other way round.

What chainring size for my terrain?

• 50/34 (compact) : the most versatile option, well suited to the mountains.
• 52/36 (semi-compact) : a balance of speed and acceleration, the most common choice today.
• 53/39 and above : reserved for flat terrain and high gears.
• In single chainring, allow for 38 to 46 teeth depending on your cassette and terrain.

Inner, outer, round or oval?

• On a double chainring setup, the chainrings inner and outer are not interchangeable : check the position before ordering.
• Chainring teeth are profiled for a specific number of speeds: match them to your drivetrain.
• Chainrings oval (Rotor Q-Rings, O-Symetric) smooth out the dead spot in the pedal stroke; the benefit is individual.

For more information: How to choose road bike chainrings

See also: Road cranksets and crank arms · Road chains · Road front derailleurs