Whats wrong with my front mech/shifter

birdy247

My chain got thrown off about 6 times today. It happens when in the big ring at the front and shifting down to smaller cogs at the back.

i have alos noticed that it is getting tricky to get the gear lever to get it into the small ring at the front. i have to shift a few gears at the back, and then it suddenly pings the front mech very viloently. Not sure if this is a shifter problem or mech problem.

i am running shimano tiagra (shifters are about 1 year old).

It almost seems the the front mech is either extreme one way, or extreme the other way i.e. chain rub in small ring, and shooting the chain off in the big ring.

Any advice welcome before i start spending money!

Thanks

sungod

try adjusting the front mech...

http://www.parktool.com/blog/repair-hel ... djustments

you'll find shimano's own instructions here...

http://techdocs.shimano.com/techdocs/index.jsp

if things are dirty it can also cause problems, either binding in the front mech itself, or the cable, the front mech is moved to the small ring position by a spring, if the cable is sticky/binding in the outer then it can degrade shifting

while you're about it, might as well check the rear mech adjustment and chain length as well

birdy247

Thanks, How would I stop the cable/mech being sticky? Is it a case of completley removing the cable and getting a new one, + degreasing the front mech spring?

how often should cables be changed?

Thanks

sungod

first try adjusting, if it still doesn't work...

take off the front mech, give it a good clean, then lube the pivots

otherwise, if the front mech moves freely with the cable undone, and/or you can feel the cable sticking, then try cleaning the outer

but for front mech it is less likely to be sticky cable than the rear, you can try squirting solvent into the outer from the top if it does seem to be sticking, but tbh this is less likely

if the cable end is frayed, don't pull it out of the outer as you probably won't be able to get it back through, or if you do, it'll damage the liner

cables can last a long time, depends on conditions, if they're not damaged then no need to change

birdy247

I have looked at my front mech and think it may actually be bent. I have attached a photo to confirm.

It is a shimano tiagra.

Thanks

sungod

it does look like it's a bit bent

take it off, give it a good clean/lube, and you should be able to straighten it out ok

birdy247

What would you suggest is the best way to straight it? A hammer job on the area that is bent?

Also, what do you think would cause this?

Thanks

Pross

Looks like it is going too far over, screw it down a bit with the limiter.

sungod

birdy247 wrote:

What would you suggest is the best way to straight it? A hammer job on the area that is bent?

Also, what do you think would cause this?

Thanks

finger power should be enough, but if there are dents in the straight bits might be harder to sort out

tbh if it's too far gone, a replacement shouldn't be that expensive

something has whacked it, foot, bike falling over, caught on lamp post when locking up, etc.