105 shifter won't trim - broken?

leepowell

I have a set of 2012 105 shifters. Tonight I noticed the front shifter won't trim properly when downshifting. Up shifting it works fine. But when coming down the mech only moves about 2mm. Another click and it jumps to the small ring as expected.

I've tried everything tonight to try and fix. New cable. Liberal GT85'ing on the mech and shifter internals. But I can't think of anything else to try.

Is the shifter likely broken?

leepowell

Added a quick video showing the problem...

https://youtu.be/MWz9aeh5GCY

k-dog

That doesn't look bad to me - the trim when in the big ring does only move the cage a couple of mm - just enough to stop it rubbing.

I would start again from scratch just to get the tension right etc and go from there.

If you need instructions this is what I use:

So first , with the cable de-attached. Put the chain on the small front ring and 25t (or biggest) back cog. - Make sure to click the downshift lever into its lowest postion.

Adjust the inner limit screw (closest to the frame on the front derailleur) so the gap is 1mm from the chain and the front derailleur's plastic plate,and not rubbing on the chain.

Clamp the cable (finger tight cable tension- not too much). Then shift the chain onto the 11t cog (or smallest) at the back, and shift the front onto the big ring. There should now be some chain rubbing on the cage if you spin the cranks.

Then wind the inline barrel adjuster (adding more cable tension) until there is a 1mm gap between the outer cage and chain, and no chain rub. Look down at the front derailleur cage as you do it.

Then wind the outer limit screw in until it just touches the stop. (start off with the outer limit screwed out, if its screwed in too much it wont shift up)

Now shift the chain onto the small front ring, and the rear onto the second to last smallest cog. Then click into the front small ring trim position. Now whilst in the trim position - add more tension again with the barrel adjuster until there is no rub. Leave a gap of 2mm from the chain and the outer cage. This will eliminate any slop in the trim position and make it feel more positive to click.

Now it should all be set. Check all gears and trim settings. Make sure the chain isnt being thrown over off the big ring.

If that doesn't do it it's more likely to be the cables or the mech than the shifter IME - they get gummed up easily - but that's a good thing because both are easier and cheaper to replace.

itboffin

Good advise to start again and wgphwn you do make sure your barrel adjusters aren't open or closed too much.

leepowell

Thanks guys. I did start again over the weekend, and all has resumed to normal. Thanks!