Bicycle Gears Explained

Introduction

• Bicycles have gears to enhance riding efficiency on various terrains:
  • Uphill
  • Downhill
  • Flat surfaces
• Importance of gears:
  • Without easy gears, climbing steep hills becomes difficult.
  • Lack of bigger gears limits speed downhill.

Parts of the Gear System

Shifters

• Located on handlebars on modern bikes (previously on the downtube).
• Function: Change gears.

Cassette

• Collection of differently-sized cogs/sprockets on the rear wheel.

Chainrings

• Turned by pedals.
• Bikes can have one, two, or three chainrings.

Chain

• Connects chainrings with the cassette.

Derailleurs

• Present at the rear and possibly front (if multiple chainrings).
• Function: Guide the chain across sprockets by moving side to side.
• Operate via:
  • Cables connected to shifters that pull the derailleur.
  • Springs that help guide the chain when changing gears.
  • Some modern derailleurs use electronic motors (servos) instead of cables.

Gear Operation

Rear Derailleur

• Contains springs and a cage with pulley wheels.
• Maintains chain tension to prevent slipping.
• Specially shaped teeth on cassette and chainrings facilitate smoother gear changes.

Gear Ratios

• Easiest Gear:
  • Smallest chainring + biggest cog at the back.
  • Example: 34 teeth chainring, 34 teeth cog = 1:1 ratio (ideal for steep climbs).
• Fastest/Hardest Gear:
  • Largest chainring + smallest cog at the back.
  • Example: 50 teeth chainring, 11 teeth cog = 4.55:1 ratio (better for speed or downhill).

Conclusion

• Gears assist in tackling different gradients and increasing speed.
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