help! - front derailleur kaput!

evsy

hey everyone

so i was out riding yesterday and as i approached a sharp climb i changed down to the small ring. when i did this the chain seemed to jam and then free itself.
rest of ride was fine but i noticed the front derailleur was further out when i change up. it wasnt pushing the chain over the big ring and off, it was actually changing fine.

any idea why and how the chain jammed??

when i got home i looked closely at it and it seems to have bent a little and is no longer 100% straight.

so basically, do i need a new one?

if i do i have a shimano 105 5600 groupset on my bike but it seems quite hard to get a 5600 front derailleur. the 5700 says it can only be used with the 5700 groupset and the 6700 or something. but is there no way the 5700 would be compatible??

thanks for any help

evsy

fludey

Is it a clamp around the frame mount? You sure it's bent and not just slipped round on the frame?
Think pictures would help, not sure about your other question sorry.

evsy

nope, its a braze on style.

will try and get some pics later and upload them.

it is difficult to tell how bent it is, it just looks much wider than it used to.

sungod

you can get them here (among other places, may be cheaper elsewhere)...

http://www.jejamescycles.co.uk/shimano- ... 92057.html

but if it has been bent you can probably straighten it ok

if the chain jammed between a chainring and the cage, assuming there's nothing wrong with the chainrings or chain, it may be that the adjustment was out

try taking it off, check the pivot and spring are ok, see if you can straighten it, if not get a new one, refit and adjust

while you're doing this, might as well take the opportunity to give the other bits the once over just in case there's anything amiss...

check the cable isn't worn or sticking in the housing

check the chainring bolts are tight

check for worn/bent teeth on the chainrings

check for any dodgy links on the chain

jermas

Sounds like chain suck (chain not disengaging properly whilst changing down, then jamming around chainring). You should be able to straighten the derailleur. Check the height making sure there is only a tiny gap between the top of the big ring and bottom of derailleur.
If you need a new one 5700 will work fine with 5600 shifters. 6700 will work even better.

evsy

thanks for the replies guys.

i have just been out for an hour and the chain went over and off the big ring once when i went to change up.

could it be the mech has some how shifted?? maybe the cable has stretched or something.

when i look down from top of bike it doesnt actually look bent.

i have checked the chain and cassette and both seem ok. and the teeth on the chainset seem ok.

what do you think?

jermas

Check that the derailleur is parallel with the chainring- it might have been knocked off line. If so;
undo cable,
slacken the clamp bolt,
adjust mech position (parallel to chainring and also 1mm height clearance on large ring),
retighten bolt.
Reattach cable making sure there's no slack (gently use pliers to pull cable whilst tightening).
If the chain is still being dropped whilst shifting up, the outer (H) stop screw will need to be turned in half a turn or so.

Garz

This coincidentally has been happening to me lately. After a few overthrowing incidents onto the crank I investigated. To cut a long story shorter, I found the barrel adjusters on the frame temporarily fixed the issue for a couple of rides (the adjuster pulled the mech in about 5mm as this was getting very near the crank with almost zero gap).

I will try the 1mm (or a penny) gap between the chainring and FD next as this does seem larger than it should be.

A couple of up-changing chain jammings from recollection started this problem.

evsy

jermas wrote:

Check that the derailleur is parallel with the chainring- it might have been knocked off line. If so;
undo cable,
slacken the clamp bolt,
adjust mech position (parallel to chainring and also 1mm height clearance on large ring),
retighten bolt.
Reattach cable making sure there's no slack (gently use pliers to pull cable whilst tightening).
If the chain is still being dropped whilst shifting up, the outer (H) stop screw will need to be turned in half a turn or so.

thanks for the advice.
i think i will drop it in to my lbs because im pretty new to biking and dont really know much about altering the derailleurs etc.

what i did notice yesterday was that when you change to big ring it pushes the chain over and off the ring, but the shimano shifter has a mid shift thing so when you are in big ring but want to change to a lower gear at the back, you click once and it slightly alters the position of the derailleur to stop excess strain on the chain. well, when i do this now it moves but only back to position of where the mech used to be when it was on the big ring.
so basically the derailleur seems to be too far over.

does that make sense??

fludey

It makes sense and tbh just sounds like the H end screw just needs turning in a little, I assume you have not altered the cable tension in anyway?
It might be worth resetting the cable tension as mentioned above on the lower ring, then adjust the H screw in a little bit at a time on the full over position on the shifter not the half way shift point.
If you need full instructions have a look on the shimano website you can download full instructions with diagrams.

LangerDan

From the descriptions, its likely that the derailleur cage side plates have flared out when the chain jammed- particularly the outer one. This is why the chain is being shot over the outer ring - the plate is no longer close enough to retain it and lets it travel a few mm further. If you look along the line of the chain, the plate is probably no longer vertical

This can be fixed easily by bending in the outer plate. However it would be safer to do this with the mech removed from the braze-on in case you bend that.