Understanding Bike Gearing
Bike gearing determines how hard or easy it is to pedal, and how fast you can go at a given cadence. Understanding gear ratios, development, and how they affect your cycling performance is essential for optimizing your bike setup.
Key Gearing Concepts
Gear Ratio
The gear ratio is calculated by dividing the number of teeth on the chainring by the number of teeth on the rear cog:
Gear Ratio = Chainring Teeth ÷ Cassette Teeth
- Higher ratio (3.0+): Harder to pedal, higher top speed
- Lower ratio (1.5-): Easier to pedal, better for climbing
- Example: 50 teeth chainring ÷ 12 teeth cog = 4.17 ratio
Gear Development (Gear Inches)
Gear development represents how far your bike travels with one complete pedal revolution:
Development = Gear Ratio × Wheel Circumference
- Measured in meters or inches per pedal revolution
- Higher development = more distance per pedal stroke
- Traditional "gear inches" based on high-wheel bicycle equivalent
Cadence and Speed
Your cycling speed depends on gear development and pedaling cadence:
Speed = Development × Cadence × 60 ÷ 1000 (for km/h)
- Optimal cadence: 80-100 RPM for road cycling
- Mountain biking: 70-90 RPM typically
- Track cycling: 100-130 RPM for sprints
Choosing the Right Gearing
Road Cycling
- Flat terrain: 50/34 chainrings with 11-28 cassette
- Hilly terrain: 50/34 chainrings with 11-32 or 11-34 cassette
- Racing: 53/39 chainrings with 11-25 cassette
- Endurance: Compact gearing (50/34) for easier climbing
Mountain Biking
- Cross-country: 32T chainring with 10-50 or 10-52 cassette
- Trail riding: 30T or 32T chainring with wide-range cassette
- Downhill: Shorter cassette ranges, focus on middle gears
- Climbing: Smaller chainring (28-30T) with large cassette
Track and Fixed Gear
- Track racing: Higher ratios (3.5-4.0) for speed
- Street fixed: Medium ratios (2.7-3.0) for versatility
- Hill climbing: Lower ratios (2.2-2.7) for easier pedaling
- Criterium: Higher ratios for sustained speed
Gear Ratio Applications
Climbing Gears
- Steep climbs (15%+): Ratios below 1.5
- Moderate climbs (8-15%): Ratios 1.5-2.5
- Rolling hills (3-8%): Ratios 2.0-3.0
- False flats (1-3%): Ratios 2.5-3.5
Speed Gears
- Sprinting: Ratios 4.0+ at high cadence
- Time trials: Ratios 3.5-4.2 for sustained power
- Flat racing: Ratios 3.0-4.0 depending on conditions
- Descending: Highest available ratio
Skid Patches (Fixed Gear)
For fixed gear bikes, skid patches indicate how many different spots on your rear tire will contact the ground when skidding:
- More patches = even tire wear
- Calculated using gear ratio and ambidextrous skidding
- Prime number cogs often give more patches
- Examples: 48x17 = 17 patches, 46x16 = 8 patches
Gear Range and Ratios
Gear Range
The difference between your highest and lowest gears:
- Wide range: Good for varied terrain
- Close ratios: Better for consistent terrain and racing
- Road bikes: Typically 300-400% range
- Mountain bikes: Often 500%+ range
Gear Steps
- Smooth progression: 12-15% steps between gears
- Racing: Smaller steps (8-12%) for fine-tuning
- Touring: Larger steps acceptable for simplicity
- Mountain: Large jumps in climbing gears often necessary
Drivetrain Considerations
Chain Line
- Straight chain line: Most efficient power transfer
- Cross-chaining: Avoid extreme combinations (big-big, small-small)
- 1x drivetrains: Compromise on chain line for simplicity
- Front derailleur setup: Affects usable gear combinations
Wear and Maintenance
- Even wear: Use full range of gears regularly
- Chain stretch: Monitor for gear skipping
- Cassette wear: Replace chain before cassette wears
- Cleaning: Keep drivetrain clean for smooth shifting
Electronic vs Mechanical Shifting
Electronic Shifting Benefits
- Precise shifts: Consistent performance in all conditions
- Programmable: Customize shift patterns
- Multiple shift points: Shift from various hand positions
- Auto-trim: Front derailleur adjusts automatically
Mechanical Shifting Benefits
- Reliability: No battery or electronic failures
- Serviceability: Field-repairable with basic tools
- Cost: Lower initial and maintenance costs
- Feel: Direct mechanical connection
Optimizing Your Gearing Setup
Analyzing Your Riding
- Terrain: Flat, rolling, or mountainous
- Fitness level: Beginner vs experienced cyclist
- Riding style: Recreational, racing, or touring
- Cadence preference: High spinner vs power grinder
Testing and Adjusting
- Track usage: Note which gears you use most
- Identify gaps: Where you need intermediate ratios
- Consider changes: Different chainrings or cassettes
- Test before buying: Try different setups if possible