Repair guides › Drivetrain

Change chainring size

The front gear. On a 1x bike it sets your whole gear range together with the cassette. Bigger ring = harder gears and higher top speed. Smaller ring = easier climbing. Narrow-wide teeth (alternating thick/thin) hold the chain on without a front derailleur. Rings either bolt on (to a spider with a bolt circle diameter, BCD) or are riveted/swaged to the crank arm, which means replacing the whole crank to change size.

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Tools

• Ball-end hex key set (1.5–10 mm): Park Tool HXS-1.2 Professional L-Shaped Hex Set ($$)
• 1/4" click torque wrench (about 2–17 Nm) + bits: Pro Bike Tool 1/4 inch drive click torque wrench set (2.2–16.9 Nm) ($$)
• Chain tool: Oumers bike chain repair tool set ($)
• Quick-link pliers: Basic master link pliers ($)
• Quick links (match chain speed): Wippermann Connex Link 808 ($)
• Torx key set (T10–T50): TEKTON long arm Torx key set T10-T50 ($)
• Digital calipers: Clockwise Tools DCLR-0605 IP54 Digital Caliper ($$)
• 3/8" click torque wrench 10–60 Nm: Pro Bike Tool 3/8 inch Drive Click Torque Wrench Set 10-60 Nm ($$$)
• 3/8" ratchet + 14/15 mm sockets + 8 mm hex bit: TEKTON 3/8 inch drive socket set metric ($$)
• Square-taper crank puller: Park Tool CCP-22 ($)
• Chainring nut wrench: Park Tool CNW-2 ($)

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Steps

1. Count teeth on your ring (stamped on it or count them) and check if it is bolted or riveted. Measure BCD if bolted: twice the distance from the crank center to a bolt center.
2. Check the Counter tab: the biggest ring is limited by chainstay clearance; any size change needs a new chain length.
3. Bolted ring: remove the drive-side crank arm (see Crank removal), unbolt the ring in a star pattern, fit the new ring with the tab behind the crank arm.
4. Riveted ring: replace the whole crankset with one in the size you want (square taper, matching spindle length).
5. Torque chainring bolts, refit crank, resize the chain (about 1 inch, one inner + one outer link, for every 4 teeth bigger; or use the big-big method: + 2 links, or + 4 links with a 42T+ cog).

Torque

Diagram

Signs it needs doing

• Chain drops off over bumps
• Hooked or shark-fin teeth
• Chain sucks up behind the ring

Problems this fixes

• Clicking or ticking when pedaling
• Chain skips or jumps when pedaling hard
• Chain falls off