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Bicycle Mechanics and Repair Decal Physics 98/198 spring 2014 Rear Derailleurs. meow. Components. Shifter. Cable. Rear Derailleur. Three Limit Screws. Adjustment Methods. Adjust in quarter turns. - PowerPoint PPT PresentationTRANSCRIPT
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meow
Bicycle Mechanics and Repair DecalPhysics 98/198
spring 2014
Rear Derailleurs
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ComponentsShifter
Cable
Rear Derailleur
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Three Limit Screws
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Adjustment Methods• Adjust in quarter turns.• Turning B-screw clockwise increases
tension, pushing the guide pulley further from the sprocket.
• Adjust the H-screw (high limit) when the derailleur is at the smallest (outermost) sprocket.
• Adjust the L-screw when the derailleur is at the largest (innermost) sprocket.
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Guide is too far. Need to turn B-Screw Counter-Clockwise
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Guide is too close. Need to turn B-Screw Clockwise
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Correct distance between guide and sprockets.
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Cable Barrel Adjuster
• Look at derailleur and sprockets from the back.
• The chain should be aligned with each sprocket as you shift through the gears.
• If the derailleur is pushing too hard towards the wheel, turn the barrel adjuster clockwise until the chain is aligned.
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Aligned Derailleur (Smallest Sprocket).
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Derailleur Hanger
Replaceable Hanger
Will sacrifice itself in an accident to keep the frame unharmed.
Non-Replaceable Hanger
Requires special attention and care. A broken hanger is often beyond repair.
The hanger allows the derailleur to be attached to the frame
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Repairing a Bent Hanger• If your hanger can be replaced, replace it.• Bend the hanger back with a wrench for
leverage. Be aware, it may still break.
Bent Hanger Repair Option 1 Repair Option 2
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Aligning the Derailleur Hanger
• The hunger must be parallel to the rear wheel• If the hanger is straight, but the derailleur
looks bent, replace the derailleur.Resources: http://www.utahmountainbiking.com/fix/rhanger.htmhttp://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment
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Aligning the Derailleur Hanger
Resources: http://www.utahmountainbiking.com/fix/rhanger.htmhttp://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment
Thread in bolt Measure distance(green) to wheel as you rotate the angle
gauge
Bend using wrench until distance is the same
everywhere
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Or use the DAG
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Pointers on Replacing Cable/Housing• Shift to gear with lowest cable tension.
Usually:
• Take note of how the cable is mounted before removing it
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Pointers on Replacing Cable/Housing• Use the old housing to determine the length
of the new one. Cut to just the right length.
• Cut housing with the correct tool. Make sure the newly-cut edges are not sharp.
Too Long Correct
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Fine Adjustment
• 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
Clockwise = screws adjuster in = loosens cable tension = Moves derailleur inward
Counterclockwise = screws adjuster out = increases cable tension = Moves derailleur outward