Front derailleur poor shifting down

rob39

All of a sudden my front derailleur struggles to shift down. Shifts up OK but only moves a fraction when trying to drop into the small ring. Nudge with my shoe to drop it down. Running Shimano 105 5700

arlowood

rob39 wrote:

All of a sudden my front derailleur struggles to shift down. Shifts up OK but only moves a fraction when trying to drop into the small ring. Nudge with my shoe to drop it down. Running Shimano 105 5700

Down change to the small ring relies on derailleur spring returning to its default position. If you are having problems with a down shift then something is stopping the spring doing its job.

Several possibilities but most likely is the inner cable is snagging somewhere either due to fraying or some problem with the cable outer. Might be worth loosening the cable from the derailleur and checking if it moves freely. Give it a good lube at the same time with oil or teflon spray.

lesfirth

I agree with the above reply.I had this problem ,the cause was the inner cable had worn a groove in the plastic guide where it makes a tight turn under the bottom bracket and the cable was jamming there.When you have the problem check if the cable is slack on both sides of the bottom bracket .

Bobbinogs

Yepp, very good responses above. Basically, if the FD is not shifting down then the spring is failing to overcome the resistance. Hence, either the cable has too much friction for some reason or the FD action is restricted in some way (the pivot points need lubing or the spring is too weak, etc.). I would suspect the former but not rule out the latter. Either way, unfasten the cable and investigate.

k-dog

This time of year my prime suspect is always just the derailleur gummed up - autumn crap followed by damp salty roads are very good at that.

I've had most success taking the derailleur off and giving it a good clean and lube until it moves freely.