Chain off and dysfunctional Front Derailleur

mattward1979

Had a Nasty crunching chain slip yesterday, and whilst I was ok to refit the chain and finish my journey, I found that the front derailleur had stopped moving close enough to the frame to shift from the Big ring to the Small....

I read up on maintenance for this, and it suggested using the screws to reallign the mechanism, but it seemed more likely to be a slight buckle of the Derailleur cage.

After a bit of pushing (nothing too aggressive!) it fixed the problem, and now it shifts ok again, but im worried that my 8 month old gear system is on a downward slope...

should everything still be ok or should I get it looked at and possibly changed?

ps, Tiagra Groupset

SLX01

Its either bent or its not! If its not working and is not physically damaged it should be the adjustment it should not be worn out after 8 months. If the chain falls off its usually because it moves too far inward if its not letting the chain drop onto the small ring it usually just stays on the big ring.

mattward1979

Thats the thing.. it dropped off to the frame, and then after refitting wouldnt shift down to the small ring again.

I couldnt really tell visually whether it was bent or not as the cage is curved anyway.

SLX01

The cage should be straight and paralell to the rings if its a band type it may have twisted on the down tube.

http://www.youtube.com/watch?v=ngm6dr-1 ... re=related

Try setting it up again from scratch and see it that makes a difference.

sungod

1st - undo the cable from the fd, check it travels completely freely in the sleeve, if it feels gritty/sticky you'll need to flush the cable housing clean, use a light solvent

personally i wouldn't apply any lube, if you do then make sure it's only very light otherwise it'll just trap dirt and go sticky again

if the cable end isn't frayed you could pull it out to simplify cleaning, but remember you have to get it back afterwards!

2nd - is the fd mechanism clean? give the spring and pivot a good clean, then lube

3rd - go through the fd adustment process from the start

http://techdocs.shimano.com/media/techd ... 606969.pdf

datpat64

I'd be surprised if the derailler was bent. More likely the clamp has moved so that the derailler isn't quite parallel. If it's a clamp type (which I think the Tiagra is) simply loosening the 6mm nut at side of seat tube and moving complete derailler round slightly should fix.

Try about 1 mm at a time then tighten and try agin to make sure it's not only dropping to small ring but moving back up as well.

If you've got any cross chaining (and bear in mind you will have if using the gears at extremes), then use the adjuster screws on the derailller. As you look at the derailler the front screw (the one nearest to you) controls the limit on the large ring and the rear screw looks after the rear (makes sure it doesn't drop off the small ring when changing down).

Best of luck

Dave