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Bicycle Mechanics and Repair Decal Mechanical Engineering 98/198 Spring 14 Lecture 4

Bicycle Mechanics and Repair Decal Mechanical Engineering 98/198 Spring 14 Lecture 4. Components. Shifter. Cable. Front Derailleur. Gear Basics. Cassette/Freewheel. Front Chain Rings. Gear Ratios. A gear ratio = number of teeth on the front chain ring

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Bicycle Mechanics and Repair Decal Mechanical Engineering 98/198 Spring 14 Lecture 4

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  1. Bicycle Mechanics and Repair DecalMechanical Engineering 98/198Spring 14Lecture 4

  2. Components Shifter Cable Front Derailleur

  3. Gear Basics • Cassette/Freewheel • Front Chain Rings

  4. Gear Ratios • A gear ratio = number of teeth on the front chain ring number of teeth on the back sprocket • Lower ratios make it easier to pedal

  5. Proper Shifting • Shift only when pedaling forward. • Avoid “crossing” the chain as much as possible. • Do not shift when pedaling hard (up a hill). Crossed Chain

  6. What are shifters? Shifters are devices on your handlebars, stem or downtube that allow you to change gears Downtube shifters STI shifters

  7. Types of Shifters Stem-mounted shifters Index shifter with integrated brake lever

  8. Types of Shifters Bar-end shifter Twist-style shifters

  9. How shifters work • 2 functional types of shifters • Indexed (Preset positions, “click” shifting) • Friction (Undefined positions, analog)

  10. Friction Shifters

  11. Index Shifters

  12. Shifter Cables Cable head can be cylindrical (modern) Cable head can be a disc (vintage) http://harriscyclery.net/product/ejac-french-gear-shift-cable-2367.htm

  13. Shifter Housing Necessary for indexed shifting Can be used for tension shifting

  14. Front Derailleur Types Top Pull Bottom Pull

  15. Front Derailleur Types Double (also clamped) Triple (also braze-on)

  16. How does it work?! Pushes the chain to a different chainring

  17. Campy EPS http://www.youtube.com/watch?v=j9SgACoEQoE Chain jumps to a larger chainring Chain falls to a smaller chainring

  18. Shifting Mechanism Possible cable directions Limit screws = Chain

  19. Installation Align the bottom of derailleur cage to be lightly above the largest chainring Angle cage by a couple degrees toward the rear of the bike Source: parktool.com

  20. Initial Set Up-Upper Limit Screw Step 1: set gears as shown above Step 2: turn HIGH adjustment screw until a small gap on the right side is achieved Source: techdocs.shimano.com

  21. Initial Set Up-Lower Limit Screw Step 1: set gears as shown above Step 2: turn LOW adjustment screw until small gap is achieved as shown Step 3: tension and secure cable to derailleur Source: techdocs.shimano.com

  22. Initial Set Up-Upper Limit Screw Step 1: set gears as shown above Step 2: turn HIGH adjustment screw until a small gap on the right side is achieved Source: techdocs.shimano.com

  23. Initial Set Up – Adjusting Shifting Step 1: set gears as shown above Step 2: turn the barrel adjuster counter-clockwise until a small gap on the left side is set. Go through all gears and fine-tune. Source: techdocs.shimano.com

  24. Setting Limit Screws Set gears as shown above Set gears as shown above Turn LOW adjustment screw until small gap is achieved as shown Turn HIGH adjustment screw until a small gap on the right side is achieved Source: techdocs.shimano.com

  25. Fine Adjustment (trim) • A properly tuned derailleur will shift between all front gears and not throw the chain off the chainrings. • Even a well-adjusted derailleur may rub in some gear combinations Counterclockwise = screws adjuster out = increases cable tension = Moves derailleur outward Clockwise = screws adjuster in = loosens cable tension = Moves derailleur inward

  26. PROBLEM #1 • Max has a problem. Recently, he found that it was much harder to pedal than usual. What could be wrong with his bike?

  27. PROBLEM #2 • Austin has a problem. He tells us that he hears noises from his chain. What could be wrong?

  28. PROBLEM #3 • Chris has a problem. He has trouble braking! The brake levers are hard to pull and the bike has no stopping power. What could be wrong?

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