Bicycle
Gear Adjustment
Adjustment
of bike gear sets is such a simple procedure however it is
something very few people know how to do properly, and the
basic principles of all gear sets are the same regardless
of how many gears you have or what type of gear levers you
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There are a
number of different factors that can cause your gears to fowl however
finding and fixing the problem generally takes little time and effort,
however it is one of the most common jobs we have to do in our shops
repair centre.
For the purpose
of this lesson we are going to strip the gears and rebuild them
from scratch, the purpose being that once you know everything is
as it should be, then regular maintenance is simple.
Gear
troubleshooting
Gears
jump all the time?
1) Most
likely cable tension, bent derailleurs or worn jockey wheels (read
Gear adjustment lesson)
All
gears jump under load?
1) Possible
stiff link ( find stiff link and repair or replace)
2) Chain
or chainwheels severely worn (replace worn parts)
Gears
jump on small cogs at back only when under load?
1) Chain
and cluster/cassette most likely worn (replace both)
2) Bent
derailleur (straightens or replace)
Gears
change down ok but not up?
1) Incorrect
cable tension (adjust cable tension)
2) Damaged
cables (repair or replace)
3) Bent
derailleur (straightens or replace)
Chain
keeps coming off
1) Incorrectly
adjusted gears
2) Bent
derailleurs or chain
3) Bent
chainwheels
4) Bent
frame or bottom bracket axle
Tools
required for complete service
1) Small
flat head screwdriver
2) Small
phillips (star) head screwdriver
3) 8,9mm
open/ring spanners
4) 4,5mm
allen (hex) keys
5) Degreaser
6) Chain
lube
7) Oil
8) Pointy
nose pliers
9) Bike
stand (to raise the rear wheel)
10) Chain
breaker (compatible to your chain)
Tools
required for tune up:
1) Small
flat head or phillips head screwdriver
2) 8 or
9mm spanner or 4,5 or 6mm allen key
3) Pliers
Note:
Tools required for the following work will vary according to what
type of equipment you have. Please check which tools you require
before purchasing them.
How
your gears work
There are seven
parts to your gear set, which are: gear levers, gear cables, front
derailleur, rear derailleur, cluster or cassette, chain rings, chain.
The gear levers are linked to your derailleurs via the gear cables.
By moving the gear levers you are telling the derailleur where it
should be, the derailleur in turn is telling the chain where it
should be. If you have a bike with index gearing which virtually
every bike now has, then if only one thing is wrong with your gears
it can effect everything. Indexed gears are where every click or
movement of the gear lever means the derailleur will tell the chain
to move one cog.
If the gears are set correctly then the chain will ride smoothly
on that cog. With the older friction system you would need to fine-tune
your gear lever movement to make the chain run smooth on that cog.
Taking
it all apart
If you aren't
confident with disconnecting your gear system then take ten minutes
or so to study the gears on your bike, try to remember wear everything
goes, read this lesson several times, draw a picture if necessary.
Pay attention to how the cables connect to the derailleurs and how
the derailleurs are connected to the bike.
When you feel you know where everything goes, place the bike on
your stand and lets get to work.
Disconnecting
the cables
Move your gears
so the chain sits on the smallest cogs front and back, now if you
follow the inner cables through to the derailleurs you will notice
where the inner cable is secured to the derailleurs.
Most of the time it is either a 4mm allen key or 9mm spanner. This
bolt is called an anchor bolt.
You may also see a thin steel or alloy cap at the very end of the
inner cable, this is called an inner cable end, and it stops your
inner cable from fraying.
Remove any cable
ends by pulling them off with your pliers then undo the anchor bolt
several turns on both derailleurs to allow the cable to release.
Some nuts on lower quality derailleurs may need a slight tap to
make them release the cable.
Your cables are now disconnected, and you will be able to pull the
inner cables straight through the outer cables.
It may be a bit hard at some points as the anchor bolts have flattened
the inner cables which will make that part of the cable tight in
the outer, if its a bit tight just pull harder.
If you can't pull the cables through then your cable is either still
lodged to the anchor bolt or may be that rusted inside the outer
that it has seized. If this is the case then just cut the cable,
it will need to be replaced anyway.
If you have STI gear levers you may need to fiddle a bit to get
the inner through the guide of the lever.
Check to see the gear lever is moved to its bottom position.
Now that we
have our cables apart we need to inspect their condition, look for
any frayed strands on the inner cable, especially at the point the
cable anchored to the derailleur and at the opposite end where the
lead end has been attached.
Any fraying is bad and the inner cable should be replaced.
Check the outer cable for cracks and damaged ends, if you have had
any rust or dirt appear on your inner cables then you will also
need to clean out the outer cables.
The outer cables are critical as to how well index gears will work,
so if they are not close to perfect condition then replace them.
Note: if you have index gearing and the outer cables need
replacing you must replace them with index compatible outer, and
that every section of outer cable must have outer cable ends.
If you need to replace the inner cable I recommend you use a stainless
steel cable, they are only a few cents more but are a lot stronger
and last much longer.
Chain
Using your chain
breaker disconnect the chain and remove from bike.
Inspect all links for loose pins or worn or damaged links.
Clean chain thoroughly and dry.
For more information on working with chains see the lesson on Clusters,
Cassettes, Chainwheels and Chains.
Derailleurs
Disconnect both
derailleurs from the frame.
If the rear derailleur is bolted directly to the frame dropout,
then use the appropriate allen key to unscrew and remove.
If the derailleur is mounted using either a silver or black clamp
then you will need to remove the rear wheel first, then loosen the
bolt on the mounting clamp and remove the derailleur.
To remove the
front derailleur, just unscrew the retaining bolt and remove. Clean
both derailleurs thoroughly then look for any wear at the chains
contact points to the derailleur.
If your front derailleur is quite old it may have two grooves worn
into the cage, if this is the case I recommend the derailleur be
replaced.
If your budget doesn't allow this then file down any jagged edges
as much as possible, this won't make it perfect but it will work
better.
Inspect all rotating parts for excessive sideways movement, replace
derailleurs if this is the case, they are about to break.
Then check the jockey wheels on the rear derailleur. Jockey wheels
are flat on the tips of each tooth, pointed teeth or angled teeth
are worn.
Note that the jockey wheels will greatly effect the derailleurs
performance so it is important to have them in good condition.
Remove jockey
wheels from the derailleur and inspect the bushes inside. If you
have top end ceramic bushes be careful not to chip the edges they
can be a bit brittle.
Clean all bushes and add a drop of oil, then refit jockey wheels
to the rear derailleur.
Check the thread on the adjustment barrel of the rear derailleur
near the anchor bolt. The adjustment barrel is the housing for the
outer part of the gear cable.
Some adjustment barrels have a plastic casing with a spring inside,
be careful not to lose the spring when removing the barrel. If the
barrel is bent or damaged it should be replaced.
Screw the adjustment barrel back into the derailleur as far as it
will go.
Chainwheels
Now inspect
and clean teeth on front and rear sprockets, Note that most current
model sprockets have weird and wonderful shapes. They are designed
this way to enable better gear shifting but sometimes this gets
confused with wear.
On front Chainwheels you may notice 2 or 4 teeth, which have the
tops missing, these teeth are located in line with the crank arm
itself. The front rings may also have fine slits cut down from the
teeth.
We have had many customers ask us to replace the chainrings because
they are cracked. The rear freewheel will also have tops of teeth
missing. If you look closely you will be able to tell the difference
between design and wear.
When cleaning the rear cluster/cassette be careful not to get any
cleaning agents inside the cluster/freewheel. This may wash out
the grease inside resulting in a freewheel service.
Putting it back together again Refit both derailleurs the same way
you took them apart but only tighten the front derailleur enough
to stop it moving.
Now look at
the straightness of the rear derailleur.
Standing behind the bike pull the cage of the derailleur around
so it points to the ground, then look to see if the cage of the
derailleur is perfectly vertical and that both jockey wheels are
in line with each other. Straighten the cage by hand if necessary
but be careful not to over bend it.
Straightness of the derailleur is also critical to the performance
of the gears so if you don't feel confident doing this then have
your local bike shop do it.
Most of us have alignment tools to make it perfect.
When the derailleurs
are straight, feed the chain back through the derailleurs and reconnect,
apply chain lube, Maxima chain wax is now the only thing we let
near our chains, it is a dry lubricant and offers more protection
than anything else we've ever used.
Do not ever use WD40, CRC, RP7, these are not lubricants they are
inhibitors, they will dry the chain out. (See clusters, cassettes
and chains).
Run a light film of grease over the inner cables and refit the cables
again leaving them sitting loose in the anchor bolts.
Note: If you use high quality cables that use Goretex do
not use grease, this can actually melt the liners. Grease will not
effect Teflon though, which is used in most cables.
You will need
to set the alignment of the front derailleur.
Working from the right hand side of the bike manually swing the
front derailleur out so the outer cage is in line with the largest
chain ring.
You need to have two to four millimetres clearance, if you have
an outer chain guard mounted to your cranks you may need to increase
the clearance so the derailleur doesn't hit the chain guard.
Now you need to align the derailleur to the outer chain ring. Looking
down on the derailleur make sure the outer cage is parallel to the
outer chainring then turn the derailleur slightly so the back of
the cage kinks slightly out from the front.
Now tighten the front derailleur. If you have a clamp type front
derailleur the alignment of the front derailleur will go out of
position.
Sorry but I had to show you where the front derailleur should be
before you tightened it. Just take notice of how much the derailleur
moved when you tightened it and readjust the derailleur so it is
in the correct position once tightened.
Now apply a drop of lubricant to all the derailleur springs.
Tuning
your gears
Now everything
is back together and as it should be, tuning your gears take a few
minutes. Make sure your gear levers are set to their starting positions
then secure the front derailleur cable. Gears never work perfectly
on all gear combinations regardless of how much the manufacturers
say they do. Better systems come close and most people can't tell
they're not perfect but we can. What I suggest you do is pick the
chainring at the front you mostly use and then match the rear gear
adjustment to that chainring. Let's say it is your outer or largest
chain ring, move the left hand gear lever so the chain runs on that
chainring. Now if we look at both derailleurs you will notice two
small screws, one marked H the other marked L. These screws adjust
how high or low the derailleur is allowed to travel. On the rear
derailleur the H screw controls the smaller cog or high gear setting
while the L screw controls the low gear or largest cog. The opposite
applies for the front, the smallest chainring is your low gear and
the largest is the high.
Now working
on the rear derailleur start pedaling the bike, if the L screw is
set correctly the chain should be on the highest gear and running
smoothly, if not we need to set the H screw. Turn the H screw left
or right to find the improvement, if you turn the screw in to far
the chain will actually move up a cog and if you screw it out too
much it will fall of your bottom cog.
When you are happy with the H adjustment tighten the rear ancor
bolt. If you have replaced the gear cables you now need to pre load
them, to do this make sure both anchor bolts are tight then pull
hard on the inner cable where it is exposed from the outer. You
are trying to stretch the cable as much as possible, do this two
or three times with each cable. Your gear cables will stretch more
in time but not as much as they normally would.
Now if your rear gear cable is drooping, loosen the anchor bolt
again and pull the cable through so it is firm but not tight. Start
pedalling again and click your gear lever one movement. Your chain
should now be running on the second cog. If it hasn't changed up
then turn the cable adjustment barrel on the derailleur anti clockwise
until it does. If the chain went past the second cog then your cable
is to tight, loosen the cable and try again.
Now change up
two or three cogs and back down again, you are looking to see if
the chain changes up and down at the same speed. If it changes up
quickly but down slowly then the cable is to tight and you need
to screw the adjustment barrel in to loosen the cable, the opposite
applies if the change up is slow, but down changes are fast. This
means the cable is to loose so turn the adjustment barrel out.
Now move your gear lever to make the chain run on you lowest gear
or largest cog. If the chain doesn't climb up then the L screw adjustment
needs to be turned out. If it changed up first time, then turn the
L screw in all the way and then back off half a turn.
Now move
down one gear and back up again, if it changes up properly then
your rear derailleur is now set. If it didn't change up then turn
the L screw counter clockwise until it does.
Now the rear
gears are set we need to match the front derailleur to the rear
derailleur. Keeping the rear derailleur set to the largest cog move
your left gear lever to it's start position to allow the chain to
move to the smallest chainwheel on the front, if it doesn't move
down then unscrew the L screw on the front derailleur or loosen
the gear cable slightly.
You now need
to set the front derailleur so the inside cage is just clearing
the inside of the chain. Once this is done set the rear gears to
the smallest cog.
Now change up one gear at the front and back down again, it may
change up ok but slow to change down, if this is the case turn the
L screw out a fraction more and check again.
Now change up to the largest chainwheel at the front while still
keeping the rear on its smallest cog.
The outer cage of the front derailleur needs to clear the chain
by about three millimetres. The reason the distance is greater on
this side is because when you ride the bike the cranks and Chainwheels
warp outwards slightly.
The last step
is to change the front to the smallest again and check that the
front gear cable is firm but not tight.
If you have indexing on the front changer you will need to set the
cable tension as you did with the rear gears.
Your gears should now be pretty much perfect but test riding will
make sure. Quite often the gears react differently when under load
so you may need to make a few minor adjustments.
When your gears
are set correctly the only ongoing adjustment you need to make is
with the cable tension.
As the cable stretches your gears will go out of adjustment so all
you need to do is readjust the cable tension using the adjustment
barrels.
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