[Biking and BMX] Help! Dodgy Gears.

[Poisey]

Ok, you crazy bike folk Maybe you can help me out...

Anyone know whats wrong with my bike when the gears keep slipping? ie. Im in 3rd gear and it changes to 4th itself. It's nearly been the death of me and a few pedestrians. How can I fix it? How much will it cos to fix?

[Blood Clot]

Tis prob jus the cables need adjusted and tightened up a bit,
Wont cost much at alpine or dales or whatever, its quite an easy job.
if you have a read up online, im sure you would be able to do it urself. !

[Sebb™]

How old is the bike? Could be that the chain and cassette are worn out.

[djtoast]

What kind of bike is it? I'm assuming it's a mountain bike...

It's almost certainly a problem with the rear derailleur (the bit that the chain snakes through under the cogs at the back) or the shift lever that controls it. I'm assuming, if it was made in the last ten years or so, it'll have indexed shifting: the lever which changes gear "clicks" from one gear to the next (as opposed to friction shifting).

There's a spring in the rear derailleur which tries to pull the chain across the freewheel from left to right (ie from lower gears to higher ones) but there's a ratchet in the lever on the handle bars that prevents this from happening except when you want, in theory. These are connected by a cable, which should be JUST tight enough to be able to pull the derailleur all the way to the left when the shift lever is all the way round, and there's a pair of stopper screw to stop the derailleur moving too far towards the wheel, (or too far away from it). If you can't get into first gear, then the cable is too lose. you'll need to move the lever all the way round (to first), push the derailleur across with your hand til it hits the stopper, then get a friend (this needs a few hands) to loosen the nut holding the cable, pull it through as hard as possible, then tighten the nut again. (The nut will probably be a 6mm allen key type, but it may not be.) The problem SHOULD now be fixed. Check the other stopper on the deraileur won't let the chain move too far the OTHER way, away from the wheel.

If you CAN currently get into first gear, then the cable itself is tight enough, but the ratchet in the lever that pulls the cable to change gear isn't. To be honest i'm not exactly sure how they work (mine are a bit special, so they're different to most)—it may well just be an easily visible screw on the lever, but it shouldn't be tricky to figure out once you know where you're looking. If there is such a screw, a half turn clockwise may tighten it enough, possibly a little more but it won't need wild amounts of adjustment.

This may make no sense at all, but it's the best i can do at this time of day!

This picture may help a little: in particualr the "cable anchor bolt" and "limit adjusting screws"

[Poisey]

God, now your asking...lol. It's blue.

No really, its pretty old now. I saved it from its dusty tomb in the garage and decided to give it a second chance at life being my chariote going back and forth from uni. I had the gears and breaks checked before I left, but obviously the guy didn't do such a great job cos I've had a few close calls with death. The breaks squeak like a no mans business, and the gears, well they seem to have been taken over by gremlins. The thing is maybe 8 years old. I got it as a young teenager, and apart from the breaks and gears it's fine. There's no rust or anything. The chain has popped off completely a few times and I've put it back on best I could. I don't think I could fix myself even with instructions. Do you kow how much I'd be looking to pay in a shop?

I'll let you know what make/model it is when I get in from uni. Thats if I get in from uni. I'm gona ride it in there just now.

Wish me luck!

[Poisey]

(PS. Sebb, hows the course and halls going?)

[Sebb™]

I'll fix it, for a price.

They're shite

[djtoast]

It really shouldn't take more than five minutes, so I doubt it would cost much at all—no more than a few pounds, for sure.

The chain shouldn't be coming off, that's very simple to fix with the two adjustment screws (or if they're set correctly it COULD be that the chain is slightly too long, and is "hopping" off—that can be fixed by taking a link out, which again is a five minute job but does need a special tool and is fiddly)

If, being a few years old, it is friction gear levers, not indexed ones, that'd be even simpler to fix, really just one screw turn.

[Poisey]

Kool, I think. I would have taken you up on your offer, Sebb, but unfortunatly Im still down in Newcastle. I'm actually quite liking the whole "bike thing" again. Wouldn't mind getting a nice shiny new one. Santa...

(need a camera more though )

[Poisey]

There is a bike place up the road I've just discovered. I take it there tomo.

[Sebb™]

Lazy bugger, do it yourself. You'll save some cash and learn something. Really, you can repair pretty much anything on your bike without training, except wheel-truing. That takes ages to learn, and you probably won't get it right. The best wheel builder in Glasgow works for Alpine Bikes.

[Poisey]

*hangs head in shame*

I don't trust myself

[djtoast]

There's a few other things that are tricky too: bottom brackets and headsets aren't the easiest.

But anyway, if you really aren't confident abot doing it yourself, that's fine; if you mess up the adjustment screws and accidentally shift the deraileur into the spokes you'll find the bike stops rather quicker than you want, and your head hurts quite a bit...

I'm sure your local shop'll sort it for nexr to nothing.

[rossfinnie]

Wheel truing's actually very very easy with the right tools! I used to work in the Edinburgh Bike Co-Op and one of the guys managed to build a full wheel in his lunch hour! The hard part with wheels is calculating spoke length, then working out your spoke lacing pattern.

One very quick fix you can use to get your gears sorted is using the barrel adjusters on the rear mech and the shifter. Basically, if your gears are slipping from low to high (big cogs to wee cogs), you need more tension in the cable, so you need to turn the barrel adjuster so that it moves away from the shifter, and do the same on the rear mech's adjuster. This is the most likely problem, due to the gear cable naturally stretching, and also the cable sliding in the rear mech's grip bolt. Basically keep turning them til the slipping stops. If you adjust them too far, your chain will start slipping the other way. Basically, you're trying to use the cable to line the mech up with the cog you want.

If you've moved the barrel adjusters to their maximum extents and it's still slipping the way it used to, your next best bet would be to screw the barrel adjusters back in as far as they'll go, then undo the bolt on your rear mech that holds the cable in, but not completely. What you'll need to do is hold the cable end in a pair of pliers and just loosen the bolt a wee bit so you can pull the cable through. Pull maybe about an extra centimetre of cable through from its original position, then re-do the bolt and try using the barrel adjusters to fine tune.

But hey, like everyone's saying, any bike shop should do it for super cheap, most bikey-minded people could sort that out in a few minutes.