105 front mech not trimming

[DWiggy]

I have a 105 front mech and it's giving me jip.

Shifting from small to large ring is ok along with the trim function in that direction.

But trimming back down to the small ring doesn't seem to work, if I half click the small lever there is an audible click and also the tension on the shifter cable decreases but the mech stays put , it should move a fraction towards the small ring to help reduce noise/chain rub (it's in the Shimano docs) when in a crossed combo (I know you shouldn't be there but hey ho)

Any ideas?

Ps I have replace inner and outer cables which massively helped with the stiffness of operation. I'm thinking the mech itself may need replacing?

 

[Smokin Joe]

Take it off the bike give it a good clean and lube first, front mechs don't often go wrong mechanically.

 

[DWiggy]

Take it off the bike give it a good clean and lube first, front mechs don't often go wrong mechanically.

Sounds like a sensible idea, I'll give it a go

 

[Roadrider48]

As long as the cable tension is set ok the problem will be the limit screw setting. It can be a small adjustment to get it moving correctly.

 

[DWiggy]

As long as the cable tension is set ok the problem will be the limit screw setting. It can be a small adjustment to get it moving correctly.

I've set the low so chain in small front lg rear with .5mm gap on the inside and the same small rear lg front with .5mm to the outside but there is no barrel adjuster on the cable! I might have to install one, it might help me out?

 

[DWiggy]

A further note when in the front lg cog the cable tension it quite high, I can twang the cable and get a note!? Is this normal?

 

[Smokin Joe]

A further note when in the front lg cog the cable tension it quite high, I can twang the cable and get a note!? Is this normal?

Yes, the cable is under tension because it is holding the mech against the spring (Which causes it to shift back down when the tension is released. You say the trim function is causing the problem, I take it the shift down to the small ring itself is actually ok?

 

[DWiggy]

Yes, the cable is under tension because it is holding the mech against the spring (Which causes it to shift back down when the tension is released. You say the trim function is causing the problem, I take it the shift down to the small ring itself is actually ok?

Yes all working fine it's just the trim towards the small ring

 

[Smokin Joe]

Then it's not the limit screw (Which never needs adjusting anyway once set) but a stiff cable (Which you've replaced) or most likely in your case a dirty mech.

 

[shouldbeinbed]

agree, if you've set everything up as you say then the only variable left is inside the mechanism, bit of grit or something hard in just the wrong place is most likely from what you say. Real outside bet could be something odd with the lever mech but I'd have the derailleur off and properly cleaned first.

 

[migrantwing]

Cable tension!

I had the exact same issue. There was the 'click' but no movement, just as you describe. Too much or not enough is what you have to figure out. Turn barrel adjusert one way, see if it helps. If not, go back to the first setting and turn the other way. It won't take much of a turn.

 

[DWiggy]

Cable tension!

I had the exact same issue. There was the 'click' but no movement, just as you describe. Too much or not enough is what you have to figure out. Turn barrel adjusert one way, see if it helps. If not, go back to the first setting and turn the other way. It won't take much of a turn.

Unfortunately my bike doesn't have a front mech barrel adjusted fitted, might add one to see if that help, cheers.

 

[migrantwing]

Unfortunately my bike doesn't have a front mech barrel adjusted fitted, might add one to see if that help, cheers.

In that case, try adding or letting a tiny, tiny, tiny bit of cable in or out at the front mech cable bolt. Only a mil either way. Grab the cable with some needle nose pliers or similar and control how much pull or slack you allow.

 

[nxn2020]

Got exactly the same thing on my allez sport with sora fitted, now off to have a play! interested to find out what's wrong now!

 

[nxn2020]

Had a little play now, found that the cable was a tiny bit too tight. Didn't touch the front mech or lever just slackened the cable so that on its loosest point it was just short of floppy. That's a technical term for not tight for the uninitiated! Hope this helps you.