Front derailleur not fully shifting

[50000tears]

My Shimano 105 front derailleur is giving me shifting issues at the moment. It governs a front 34/50 crankset.

It shifts fine across both rings but not fully either way. When shifted to the big ring it doesn't shift far enough over and the 3 biggest gears will rub the derailleur. When this happens I can usually, not always, force it across by giving the shifter another bump to get it all the way over. When in the small ring it rubs the derailleur when on the easiest gear and I cannot correct this when on the bike.

For both of these shifting problems I can move the derailleur to the right position by hand, obviously pretty useless but shows that it is not a barrell adjustment needed or the limit screws but something else.

Can anybody help with this?

 

[Roadrider48]

That usually is a limit screw problem.
Cable tension?
If not, then a faulty/bent front mech.

 

[50000tears]

I was wondering about cable tension so will look at that first. Is a newish bike and have never dropped it so nothing should be damaged and used to work ok.

 

[Globalti]

Check the cable is working freely and the tension is adequate and adjust the limit screws.

 

[uclown2002]

+1 for cable tension. Needs to be tighter for it to shift further. I've had this exact problem recently when I brought my good bike out of winter hibernation.
If it's rubbing in easiest gear then adjust low limit screw a touch.

 

[50000tears]

Thanks guys I'll give it a crack later.

 

[Unimaginative]

There are a few good videos on Youtube on dérailleur adjustment; I found that starting from the beginning was the only way to sort my front dérailleur out properly.

Put the shifter to the position for the low ring, undo the bolt to release the cable from the dérailleur, align the dérailleur at the correct height and angle, adjust the low limit screw (and high limit screw if you can manage it), wind out any adjusters and then wind in one to two turns (so you can adjust cable tension up and down), put some lube down the outers, yank the cable with your fingers at the bottom bracket a couple of times, then re-attach to the dérailleur being careful to put the cable in the correct place - there is a bump on the frame side that the cable goes above and a valley on the top/outside for the cable to sit in; the cable should be finger-tight tensioned. You can then sort out the cable tension to de-rail the chain onto the big ring (and back) by adjusting the adjusters, making sure to check the movement both up to big and down to small.

 

[Nigelnaturist]

@50000tears if I have read this right its rubbing on front large and rear large and small front small rear, whilst a double should be able to be set up without rub on these gears, its not a good idea in practice as you will be putting undue strain on the chain, however as has been mentioned cable tension does seem to be the issue on the the large front ring, try adjusting the barrel adjuster a little first (clockwise to apply more tension), if this works and it still rubs on small the low adjuster will need adjusting on the front.

 

[50000tears]

Thanks guys. Tried to adjust the cable tension and failed utterly. I know that these small mechanical issues are simple for most but for some reason I lack even these basic skills.

Anyway my LBS has the bike now after I left the derailleur unable to shift at all after fiddling with it, and I get it back tomorrow. Thankfully he is only charging me a fiver so not going to worry too much over that.

 

[compo]

When you get your bike back avoid using gears small front with small back and large front with large back. It isn't unusual for the chain to rub the front derailleur a little when using these combinations even on a correctly set up system.

 

[50000tears]

When you get your bike back avoid using gears small front with small back and large front with large back. It isn't unusual for the chain to rub the front derailleur a little when using these combinations even on a correctly set up system.

I am pretty good with this most of the time and never use the ultimate small/small or large/large combinations.

 

[Graham]

Any chance the front derailleur is simply seized or very stiff? The rivets which are supposed to allow the derailleur to move can't easily be lubricated. After a winter of neglect Mine gradually got stiffer and stiffer and it was a real effort to move onto the big ring. Likewise because it was seizing up it didn't move all the way over when changing down. If you compare an old derailleur with a new one you'll see what I mean if you try to move them with your hands.

Hope the lbs get it sorted.