Jumping gears

[Yellow Fang]

I'm despairing of fixing the gears on my MTB. I just can't get them to shift and stay in gear properly. I've put on some cheapo SunRace 8-speed rapid fire shifter after I broke the last pair, but I don't think it's them. I also bent my gear hanger recently when the chain pulled the rear-mech into the wheel, which I think was due to a duff chain link. I've tried straightening it out, but it's a steel frame and I'm not totally sure it's right. I don't think it's the rear mech either as the spring still seems pretty strong. It might be it still needs replacing because I got a new chain. When I cycle along in a mid gear, the chain starts to jump whenever I put any real pressure on the pedals. When I shift from gear 2 to gear 3, it moves straight to gear 4. When I shift to gear 8, it might get there some time, but not immediately. It's a total dog at the moment.

 

[marinyork]

Broken axle, worn freewheel and chain was what was causing it on mine.

 

[02GF74]

put bike upside down on its saddle. what happens when you step trough all the gears on the cassette?

if the chain jumps off any sprocket, then more investigation is needed.

I take it your gear shifter is compatible with the rear shifter?

the amount of gear cable the shifter releases or pulls together with the rear shifter design determines the position of the chain. if it does not match spacing of cassetter, then you wil l experience the sort of problems you are having.

ofcrouse this assumes there is nothing fault or worn.

 

[Yellow Fang]

Cheers, when I put the bike upside and shifted through the gears, it eventually seemed alright. I didn't have much confidence in it though, and when I tried cycling on it again, they started jumping.

I don't think it's the gear shifter, but it could be. I've just changed the cable again, so I doubt it's that. It might be the derailleur, but it seemed reasonably springy. It could be I haven't quite bent back the gear hanger to how it was. I would be infuriated if I bought a whole load of new bits, just to find it was the gear hanger out of place. I suppose that's an advantage of replacable gear hangers on aluminium frames.

 

[gwhite]

If the hanger is not plumb then you're wasting your time trying to adjust the gears. Take it to a shop as they have the alignment tool and it's not a big job as it just means unscrewing the rear Der.

 

[Yellow Fang]

I took the bike to the shop. He reckoned it was the screw that holds the derailleur against the rear hanger was not tightened up properly. He didn't try straightening out the rear hanger any more, as he didn't want to risk breaking it off. He's not a fan of steel frames. I cycled it back but the chain's still jumping. I think it might be some of the sprockets are worn. I replaced the chain but not the cassette. The chain tends to jump most in gears 5, 6 & 7, and these are beginning to look like shark teeth. The chain line looks fine when in these gears, so I can't see how it can be the hanger causing the problem. I've tried adjusting the derailleur with the barrel adjuster to adjust the chain line, and it doesn't seem to have much affect on the jumping.

I'm wondering what my options are, as I'm a bit skint and don't want to waste too much more money on it. I have a spare 7-speed shifter so I could replace my current 8-speed cassette and buy a 7-speed cassette. Presumably I could get away with the hanger not being quite so straight with the sprocket spacing not being so tight.

I could convert to single speed using a chain tensioner. I'm wondering whether I could use a single sprocket on the back, my three ring chainset on the front and a chain tensioner, or whether the chain tensioner wouldn't be able to cope with the changes in slack.

I could also just get another 8 speed cassette I suppose.

 

[Yellow Fang]

Turns out it did need a new cassette, at least that was part of the problem. I thought that talk about having to replace the chainset whenever you changed the chain was an old wives' tale put about by bike shop owners.

 

[beanzontoast]

Not necessarily an old wive's tale, though when I asked about a new chain a while back, my LBS did say they would need to look at the other components first to see what else needed changing. You could take this as sensible concern or as an opportunity for them to make more money, depending which way you look at it.

Up to now, I've taken the approach of allowing all my components to wear together and, having reached the point where my favourite gear has started jumping, am just about to change the lot - cassette, chainset, chain, rear mech jockey wheels (30+ years old) and bb. None of the components I'm replacing cost much, and it's only recently that my favourite gear has started giving trouble. Bike does 5-8000 miles a year, so really can't complain.

In future though, I intend trying regular chain changing. I've bought a steel rule so I can measure my chain for stretch and change it as soon as it reaches the tolerance limit. This should extend the life of the cassette and chainset, but I haven't worked out whether the cost of chains will offset this.

 

[Theseus]

Depends how often you change your chain. Get a chain measuring tool and check the wear on a regular basis. I would rather spend a few quid on a regular basis replacing worn chains than spend big money on replacing an extremely worn chain and the complete drivetrain