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Lubrication
Remove any accumulated dirt from the freewheel with a brush and a degreaser. Disassembly
of the freewheel is a complicated procedure requiring special tools, and should be left
to a specialist. Apply oil to the freewheel whenever you lubricate the chain, taking care
to wipe off any excess.
Coaster Brake Hub
Many BMX style and other children’s bicycles are fitted with a coaster hub brake in the
rear wheel. This type of brake offers the advantages of reliability and easy operation. The
brake is operated by applying back pedal pressure and allows the rider to ‘coast’ without
pedaling, if desired. There are several models of coaster hubs available, and the internal
mechanisms are very complex. They require infrequent attention as far as lubrication,
adjustment or replacement of internal parts; if needed, this should be left to a specialist.
Keep the coaster hub sprocket clean and oil it along with the chain.
Make sure the brake arm is correctly attached to the chainstay with the brake arm clip.
The brake will not operate otherwise (Fig. 4.14).
Derailleur Systems
The derailleur system includes the front and rear derailleurs, the shift levers, and the
derailleur control cables, all of which must function correctly for smooth gear shifting
to occur. There are several different types of derailleur systems but all operate using
similar principles. For the rear shifter, there will be a positive “click” for each gear.
When properly adjusted, one click should change one gear at a time. For the front
shifter (if equipped) some shifters are a “friction” system, where you move the shifter
until the desired shift occurs. Others have the same audible “click” to indicate that
one gear has been changed. The adjustments are similar.
Inspection
The operation of the derailleur system should be checked at least every month. Check
the operation of the rear derailleur first, then the front. The rear derailleur should shift
the chain cleanly from one cog to the next without hesitation. Each notched position in
the shifter must equate to a new gear position. After shifting, the rear derailleur should
not rub on the chain. The derailleur should never cause the chain to fall off the inner or
outer freewheel cogs.
MAINTENANCE
Brake arm clip
Brake arm
Spocket
4.14
Stretch
Pre-stretch the
derailleur cables
to remove slack
4.15
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