If your gears aren't working perfectly when you're out riding it's not the end of the
world, but it is hugely frustrating. It might be that when you press your gear shifter,
the gears don't move at all. It might be that you shift two gears when you only wanted to
do one, or it might be that your chain is jumping on a particular gear when you sprint
out of a corner or put your chain under load. However, rather then let it ruin your ride
completely, why not just stop on the side of the road, because it could be something
that's very easy to fix.
Problems with badly adjusted gears aren't just confined to people with old, worn out
bikes. It might be that you've purchased a new one recently or replaced the cables on
your old bike and that they're not very well adjusted a couple of weeks later. And there's
a reason for this - that is that the inner gear cable, despite being metal, will stretch
over time in those first 2 or 3 weeks once you've used the bike, and when the cable stretches,
it means it puts the front or rear mech just slightly out of kilter.
To find out if it is a cable stretch or cable tension issue, it's quite easy. First things
first: put your chain onto the smallest sprocket on the rear wheel there and then use your
gear lever to just go up one gear. If you find it doesn't jump up a gear when you press
the gear shifter, or you get that familiar chattering sound as it's trying to jump up
onto the next biggest sprocket, the likelihood is the cable tension needs to be more. That's
a very easy thing to do - some old road bikes you might find that there's a barrel adjuster
here by the cable stop if it's external routing, but on almost all modern bikes, except those
with electronic gears, you'll find a barrel adjuster here by the rear mech or rear derailleur.
To increase the tension in the inner cable, you need to wind the barrel adjuster out,
which of course means anti-clockwise.
Just give it quarter or half a turn, try again, and just keep doing it until it jumps up onto
the next gear. Once that's happened, try it again, on to the next biggest sprocket, still
not quite going in smoothly - you can hear that chattering there as it's trying to jump
up onto that sprocket.
Once you've got it up to the second sprocket there, try going back down to make sure the
adjustment is OK going back down the other way. It's sometimes easier just to get back
on the bike and do this up and down the road.
If you get down to that smallest sprocket at the back, you wind this barrel adjuster
right the way out and it still doesn't give your cable enough tension to move it up onto
the next sprocket, I'm afraid you're going to have to go back to basics and actually
use a tool this time, because we need to actually manually tighten the cable here where the
bolt here closes it tight.
To do that, you'll need to reach into your pocket and grab the allen keys that you took
out with you. In general you'll need a 5mm allen key. Again, put the chain all the way
down in to the very smallest sprocket at the back. Push the rear mech manually up the cassette at the back.
What this will do is relieve even more
tension and give you even more slack, and that makes the adjustment that we're about
to do that bit easier.
Undo the cable here. It only needs to come through just slightly. Tighten it back up.
When you turn your pedals, hopefully it will still drop back into the smallest gear, but
there should be a bit more tension on this cable - you can see the action that's having
on the rear mech there, that means that when you start pressing the gear up, it's
going to move.
Once you've got that cable tension back using that bolt, don't forget that you can make
small adjustments using the barrel adjuster on the rear mech and that should fine-tune
your gears.
If you find that your gears are very well adjusted and they're moving up and down the
block nicely, but you can't get into the extreme big or extreme small cog, it might be that
you need to adjust the high and low adjusters on here. For this you've going to need a screwdriver,
I'll need a flathead. The 'H' stands for 'High' and that's for the small sprocket here and
the 'L' stands for 'Low', which is the biggest sprocket all the way up here. These screws
are very important for general riding, because they stop the mech from going too far either
way. It's important that they're well-adjusted, but if they're too far pushed in, it will
mean you can't get into that last gear, so if that's the case, for example you can't
get into your smallest sprocket, just undo the 'H' bolt, very slightly, you might not
need too much of a turn, again a bit of trial and error will be needed. Give your pedal
another turn and you'll see that it's gone in.
OK, next scenario - your gears are going very well, but only in one direction. You can push
up the gear very nicely, but they won't go back down very well, or vice versa. This probably
means that you've got sticky cables - there could be various reasons. Often we get grit
inside the outer cables, which means the inners just don't flow in and out very
nicely, or it could be that you've got a spring which has worn out here on the rear mech,
or it could be that you've got a worn-out chain, or worn-out cassette or worn-out chainrings.
Various things that could be the problem. Very difficult to fix this while you're out
on the trail, but our recommendation to you would be to make sure the gears work well
on the way down to the smaller sprockets because you do have a degree of adjustment here at
the front where you can just give it an extra push without clicking up to an extra gear, and
that might encourage the rear mech to push the chain into the next sprocket.
Another thing which can majorly affect the indexing of your gears is if you've managed
to bend your rear mech hanger somehow. Could've happened in a crash or while you've put your
bike into the car. Either way - it's going to be difficult to fix while you're out, but
this is again where the Hi and Lo stop screws will really be your friend. Screw them right
in to make sure that the rear mech is not able to go towards the spokes - if it does
and it gets caught, then the wheel can rip it completely off, so make sure that you adjust them so
that it's nowhere near.