Front mech woes

[trio25]

I went out on the winter roadie yesterday and it wouldn't change into the small chain ring at the front, it wasn't really a problem as the ride was basically flat. So today I'm trying to fix the problem. It seems to be at the mech, basically I change at the levers, the cable goes slack but the front mech doesn't move. I've tried cleaning it, putting a bit of lube on. But no idea what to try now. Was hoping to do a long ride today, now thinking this is not likely to be on the cards.

 

[tyred]

If you're satisfied it's clean and oiled and free, I don't know the correct term but there is a limit stop screw to adjust how far it can shift in without throwing the chain. Have a look at this first. Logically if itwas working before it should still be okay but when mine stopped changing into the small wheel, the limit stop needed adjusted. Can't explain why though.

 

[fossyant]

Can you move the mech by hand.... does it move freely - if not it's the mech, if it does, there is a problem with the cable.

I'd say it needs a good soak with WD - winter bike, possibly corroded/seized pivot

 

[trio25]

No its not moving freely by hand. I'm thinking that might be the problem, it has had a fair few hard miles over the last couple of winters.

 

[Christopher]

sounds like it has seized. I'd unbolt it from the frame, leaving the cable attached as that seems to be okay, then drop it into a tin (like an old baked-bean tin) filled with degreaser (like diluted Muck-off), leave for a few hours, drain the mech and try and uncrack it (get it moving) by hand.

If that does not work then I'd chuck it and get a new one - front mechs are really cheap unless you get the fancy ones.

If it does work then use nice fine oil (I use sewing machine oil, lovely stuff) on the pivots, remount, check limit screws and shifting.

 

[trio25]

Doesn't seem to be working, a new one might be in order.

 

[mickle]

They do seize, Deore are the worst for it.

 

[peanut]

did you check the cable guide under the BB ? they get a lot of crud during the winter and frequently sieze up with rust and grit. Check also the cable runs are nice gentle curves and not bent where they enter any cable guides

 

[fossyant]

Trio checked moving it by hand - it didn't easily.....so that won't affect the cable travel on a road bike !

 

[peanut]

Trio checked moving it by hand - it didn't easily.....so that won't affect the cable travel on a road bike !

they have a strong spring and tiny turning moment so are very difficult to move when connected, certainly never easily anyway however point taken.

If it was working before I'd be inclined to check the cage hasn't been knocked out of alignment or buckled .
They are so cheap its hardly worth spending much time with really. I can't see the pivots rusting up myself .If they did there would be virtually no movement at all

 

[trio25]

There is virtually no movement and it is hard to move at all. Anyway took it to the bike shop today and after telling them everything I had tried they said I needed a new one, they don't have one, so one is arriving on wed and will be on the bike for me by lunchtime. Nice to have a good shop nearby!

 

[marcdominic]

What solvent would anyone recommend to free a seized front mech over the weekend. It was replaced (Shimano XT) in 2006 after the original (1999 Kona Caldera Shimano XT) also seized.

I’ve heard diluted ‘Muc-Off’ might do it. Anything I need to be aware of whilst soaking…? I’ve new cables (outer and inner) to fit if I can get it working…

 

[Christopher]

If the mech is free of cables then just drop the whole thing in muc-off and cross your fingers!

 

[gbb]

If the mechs simiar to a Sora, this happens nearly every year to me...
On the mech is a largish dome headed bolt, this is where it pivots. Its rearward facing on the Sora. Undo the bolt a little (with an allen key), squirt in some WD40, manipulate the mech by hand until it frees up, then tighten the bolt.

 

[jpembroke]

I had a seized 105 front mech - it had been left in the parts bin in the shed for a while. I sprayed it with GT85, attached it to the bike and spent some time just pulling the thing until it freed itself. It's fine now.