id2d

Hi

I just bought a second-hand bike and am trying to adjust it but quite new to bike mechanics.

on the left I have a thumb-shifter with 3 settings.
to move it into 3rd gear takes a monumental thumb-push which still has my thumb aching hours later.

I tried the barrel adjusters but any movement either way seems mess up the shifting.

When I watch the gear shifting I see that the front derailleur moves into the correct position when the thumb-shifter has travelled halfway through its journey. The rest of the movement to the point where the the thumb-shifter locks does not move the derailleur at all and is just hard effort on my thumb.

Any help greatly appreciated.

mconlonx

Could be anything: bad cable/housing, high limit screw set too tight, maybe either of these combined with a FD that's not aligned to the chainrings properly.

Check here for help: Park Tool repair help -- front derailleur adjustment.

FastJake

Ah, the joys of front indexing. How is the position of the FD in the 2nd position? My guess would be too much cable tension, but if it's correct in position 2 that's not the fix for it. It's possible your shifter isn't matched to your derailer.

dsbrantjr

id2d: You are not alone, I have 2 bikes with a similar issue, one with new Shimano hardware and one with the original Suntour. The best I have been able to do is to loosen the high limit screw somewhat but not enough to spill the chain to the outside. It still takes a firm push to get the shifter to lock. It seems to be better if I use a snappier motion rather than a gradual shove. If I loosen the barrel adjuster the shift to the middle isn't far enough over. I just live with it.

id2d

hi

Thanks for the feedback the bike is a Claude Butler D24 which seems to have all original parts.

Shifting between all gears seems to work perfectly with everything aligned when it should be at the current tension but if I loosen they don't which is why I don't think that's the problem.

It's just that last bit of push I have to give to get the shifter to lock in 3rd that takes all my strength.

Jeff Wills

OK- exactly which model bike, front derailleur, and shifter are you asking about? If you don't know how to describe them, post pictures.

Regarding your problem: with Shimano parts, there's two different amounts of cable travel used. There's derailleurs and shifters made for each, and mixing them creates problems like you describe.

FBinNY 

I'll bet two beers that the cable is mounted to the inside (toward the fulcrum) of the anchor bolt. This effectively shortens the FDs lever arm, increasing the cable response ratio beyond the original design spec. and causes over-travel that you're restricting via the outer limit screw.

A bit of over-travel is designed in, but anything beyond that causes what the OP is describing.

BTW- sometimes the same problem is caused by mis-matched components so you have a front derailleur with too much cable response for the levers. If the cable is already to the far side of the pinch bolt, come back and I'll offer some Plan B solutions to spare that left thumb.

pat5319

A lot of these things have a "friction" setting may help

Jeff Wills

The OP was describing a shifter that takes a thumb-push and has 3 settings, which to me is a Shimano-type "Rapidfire" shifter. These don't have a friction setting.

FBinNY 

I'm still waiting to find out who's buying the beers.

id2d

Thanks everyone for the replies.

When I have spare moment I'll take some pics of the setup and then if nothing looks amiss I'll just have to go though a complete re-adjustment of all the screws/bolts etc.

Looigi

One thing I've come across that can cause this is Gatorade contamination of the shifter cable guide under the BB.

curly666

Have you tried lubing the cables?