Having problems with the Tiagra front mech on my caad8. Thought it was just clogged with crap but I gave it a good clean out today and it still won’t budge. Seems to just be stuck in one position – I have to either have it stuck on the big ring or small ring. If I’m on the big ring it’ll shift down if I kick it inwards with my heel.. any ideas? Getting increasingly frustrated with it now.

Cables seem fine, they don’t snag at all with the mech disconnected. Thinking maybe its the h+l screws but I have no idea what to do with them really.

Pivots are nearly siezed

I’d suggest salt corrosion??
Give it a good soak in GT85 & move it from ring to ring with your hands. Hopefully that will free it up.

I think it’s unlikely to be the H & L limit screws if the mech moves to the small ring when you shove it with your foot.

Does that mean new mech time or is it somehow fixable? I gave it a good blast with GT85 then soaked the whole lot in 3-in-1 to try and free it up but didnt seem to work.

Could be salt corrosion, I used it all through winter.

To be honest, with the amount of effort you’ve put into it already it’s probably just worth getting a new one, a tiagra front mech on crc is a tenner.

Take it off the bike and soak it in diesel for a few days, manually moving it back and forth. Then flush it with some wd40 and work it in by moving the mech again. Then follow up with some chain lube. Really give a good soaking.

get an Ultegra front mech

much more resistant to wet weather / corrosion, without the expense of going to Dura-Ace, which shares the same technology in the coating used on the pivots

Has the little bit that the spring braces against snapped off? Mine did it once in cold weather, just overnight when left in the shed, and seemed very similar in what it did (wouldn’t shift unless kicked).

Like this:
http://citycyclingedinburgh.info/bbpress/topic.php?id=2719l

Mine does this too, the underlying issue is that they’re shit. +1 to replacing with Ultegra!