In
this section we'll address common maintenence and repair issues.
For more advanced procedures we recommend you either see your
local bicycle mechanic or consult a good bike repair manual.
Table of contents includes page-jump links:
Front
Derailleur
-
Tuning front derailleurs can be a bit tricky. They are, at
best, a comprimise between sharpest shifting and most range.
The front derailleur cage that surrounds the chain must be
positioned near the chain when it's on the smallest cog so
that the cage can effectively push the chain over to the next
cog when shifting. With this positioning of the cage you may
encounter some chain rub when it is on the smaller cogs in
the rear. Technically, Shimano shows certain front/rear combinations
as unusable. However, in practice most riders will adjust
their front derailler for the best comprimise between effective
shifting and least chain rub. There is a certain range of
balance of these aspects that allows some personal preference.
For example, you may find that you will only occasionally
use smallest front cog in combination with the largest rear
cog (this is the lowest gear ratio available on your bike)
and therefore can accept a little more chain rub in with that
combination in order to make front shifting a little quicker.
To
tune front derailleur:
Place
chain on smallest cog (farthest inboard) and give shifter
a few extra clicks to be sure all cable is out.
Loosen
cable from cable clamp on derailleur. This will allow
you to set derailleur cage without influence from cable.
Use
stop-limit screw to set the position of the derailleur
cage. Careful, on some derailleurs this is the inboard
screw and others it is the outboard one (all should have
2 screws, but position varies).
Now,
reattach cable and tension just ot the point of being
taut. Check shifting. If it won't correctly, you may need
to re-position the cage or adjust cable tension. It's
a good idea to try shifting with the chain on different
rear cogs. The front may not shift as well with the chain
on different sections of the rear cogset.
Shift
out to the largest cog and check outer stop limit. Again,
stop-limit screw is in different position on diffent models.
Outer stop limit should be set to allow easy shifting
onto outer cog, but prevent overshifting that would cause
the chain to go past the cog.
Rear
Derailleur - Once stop limits
are set they rarely need to be changed. Ghost shifting or
skipping over a gear, especially on the rear, is usually a
matter of the cable loosening up a bit. Your cable will stretch
during break-in (the first month of so). If you start experiencing
problems with shifting again, it's probably because of this.
Taking slack out of the cable will usually solve shifting
problems once the stop limits are set. Barrel adjusters will
work to a point, but you may need to pull more cable through
the clamp when all available adjustment range on the barreladjusters
is used. Make sure you run the barrel adjusters all the way
in before pulling more cable so you have all that extra adjustment
room if you need it afterwards.
To
tune rear derailleur:
Shift to smallest cog. Again, make
sure all the cable is out by clicking the right shifter's
trigger a few times.
Detach cable
at clamp on rear derailleur.
Set outer
stop limit with inner adjustment screw. You should be
able to look from behind and line-up the cog with the
pulley on the R/D.
Reattach cable
- similar steps top F/D - taut cable, but not to the
point of pulling the R/D towards the next cog
Shifter all
the way up to the largest cog. Be careful when you get
to the last one to make sure you don't overshift and
put the R/D into the spokes (could happen if the inner
stop limit adjustment screw has been changed).
Use outside adjustment screw to set
inner stop limit. Push on the side of the R/D to make
sure it goes not further than the large cog (you could
actually do this step while the cable is off in step-3
if you can hold the R/D all the way over).
Any minor adjustment at this point
should simply be a matter of tensioning the cable a
little more if it needs it.
