Youth Bike Gear Calculator

Optimise gearing for rollout-restricted racing. Click a configuration in the ranking to see its full gear table.

Disclaimer This tool is provided for guidance only. Always verify any configuration with a real-world rollout measurement before racing. Racing regulations vary by event, region, and category; confirm the current rules with your event organiser or commissaire. The authors accept no responsibility for race penalties, mechanical issues, damage, or injury arising from use of this calculator.

Bike Setup

Wheel Circumference (mm)

700c × 25mm ≈ 2109mm

Race Rules

Rollout Limit (m)

Max Cogs to Block

Consecutive from smallest cog (derailleur H-limit)

Gearing Options

Chainring Sizes (comma separated)

Cassette (comma separated cog teeth)

Cadence for Speed Calc (RPM)

Display

Show in Gear Table

Chain Angle Warning Threshold (°)

Chain Angle Danger Threshold (°)

Exclude high-angle gears from rollout calc

When checked, gear combos exceeding the danger threshold are not considered for max rollout

Advanced Bike Setup

Chainstay Length (mm)

Typical road: 405-420mm

Inner Chainring → CL (mm)

Outer Chainring → CL (mm)

Distance from frame centreline to each chainring

Hub OLD (mm)

Locknut → 1st Cog (mm)

Cog Pitch (mm, centre-to-centre)

10-speed: 3.95mm

Best Configurations

Ranked by proximity to rollout limit. Speed loss and distance loss per km compare to a rider at the rollout limit, both spinning at the same cadence in top gear.

#	Chainring	Block	Smallest Avail.	Max Rollout	Gap to Limit	Speed Loss	Loss / km	Rollout