slipping gears

TheSloog

My winter bike (a nice early 90s Ciocc for anyone interested) shifts up and down when in the middle of the cassette. It's a standard double chainset with (probably) a 11-25 block on the back. Any ideas why? Friction shifters on the downtube btw.
Cheers

pinno

Have the friction levers lost their friction? ie Are the levers slipping? Only takes a small shift to loose the gear. I presume the gear wants to shift downwards? This would indicate that they are worn out.

desweller

Ghost shifting could be lots of things.

At this time of year you are probably looking for gummed-up cables.

I have also had seized derailleur pivots and rear hub problems that affect shifting if allowed to get bad enough.

Sounds like you look after the bike, but if you are lax with maintenance then debris buildup on jockey wheels or cassette can make shifting difficult to control because the chain does not sit on the sprocket properly.

I imagine it's a steel frame? So probably no derailleur hanger; if you do have one then it's worth checking to see if it's bent or loose.

TheSloog

Thanks for the replies, the gears are fine on the smallest few and biggest few cogs (of nine) and the levers seem to work well. It's just in the middle two or three cogs that they shift by themselves. The groupset is a bit of a hotchpotch but I can't see any reason for such behaviour given that it's not indexed shifting.

k-dog

A worn cassette can do that too - and the middle gears are generally used more than the others.

southdownswolf

k-dog wrote:

A worn cassette can do that too - and the middle gears are generally used more than the others.

Obviously time to replace the bike then

pinno

southdownswolf wrote:

k-dog wrote:

A worn cassette can do that too - and the middle gears are generally used more than the others.

Obviously time to replace the bike then

Heathen. It's a Ciocc.