Front 105 shifter wont drop going uphill.

Jumpy

Hi All,

I thought I might get some insight here before I put the bike in for a service.

The left 105 shifter I have appears to be set perfectly. I have adjusted it so it changes perfectly on a flat surface. However it will not drop gears while cycling uphill. Its infuriating at this point as no matter what adjustements I make it will simply not work.

It will change perfectly if I stop pedalling, but this is not ideal when climbing.

I had a member of the road crew at the Rebel Tour tell me that this is a known problem with this batch of 105s but I can find no other evidence online, also my local shop says he has never come across this.

This started happening in the middle of the Sean kelly. It is not something that has been on the bike since purchase.

Home:Ballyhoura

I presume you already know that you should ease off the power when changing gears. This is not always easy when cycling uphill but try and put in a couple of power pedals beforehand so you can slightly ease off to give it a chance to do the business. It becomes natural after a while, but also try to anticipate gears you will need before hitting a hill so you don't get caught out! (This is just one thing that sprung to mind if you are 100% sure you have it set up perfectly using the limit screws etc)

short circuit

The front derailleur is the one which has the more stressful job of shifting under load. It is not recommended to shift it going uphill. Not sure if it really is a problem or just a "feature".

When you shift going uphill, is the cable going slack and the derailleur refusing to fall ... or does the derailleur move, but not enough causing chainrub in the big chainring.

Jumpy

short circuit wrote: »

The front derailleur is the one which has the more stressful job of shifting under load. It is not recommended to shift it going uphill. Not sure if it really is a problem or just a "feature".

When you shift going uphill, is the cable going slack and the derailleur refusing to fall ... or does the derailleur move, but not enough causing chainrub in the big chainring.

It clicks and thunks like its working normally but the chain does not drop.

I have to change up again then back down while not pedalling.

This worked as expected up until the Sean kelly, during a fairly small climb. It has not worked since.

papac

I had a similar problem years ago and it did my head in for ages. Turned out the derailleur had spread a little bit.i.e the sides-the bits that push the chain- were further apart than they should have been.I squeezed them together gently with a pair of pliers and it worked fine again.

Not saying this is your problem but worth checking I'd say.Maybe you could measure with known good one against yours with calipers or a good rule.Afair I only had to squeeze mine in a few mm.

Seems possible to me that changing down under load when the chain is reluctant to move might actually bend the derailleur cage open a tad.

Turbulent Bill

I had front derailleur shifting problems with a new 105 group too, turned out the cable tension was too high. Mine happened all the time though, not just on hills.

I think the same 105 front derailleur is used for doubles and triples, so it's possible to mis-shift onto a non-existent ring if it's not setup correctly. Whatever you do, don't force the lever - a friend broke his shifter that way, expensive to replace. I'd give it to a competent LBS to sort out.