"Another" shifting problem...

parkinpants

Been having erratic shifting on my road bike for a while now and finally got round to taking a proper look.

The best I can get it after adjusting the barrels is...
- perfect descending from top cog to bottom cog, and...
- perfect ascending from bottom cog to top cog EXCEPT I have to push the lever a little bit further than the 'click point' on every single click. So I don't have to push all the way to the second click, but I always have to patiently guide it further than the click point until it moves.

If I retune it so that it ascends properly to the 'click point', it struggles to descend on each gear (suggesting too tight)

I replaced the gear cable and outers about 6 months ago. It was shifting okay at first, but probably went off kilter about 4 months ago.

I do have a fault with the mech in that the thread for the barrel adjuster is worn so the barrel adjuster isn't threaded in, it just sits on it loose, which 'maybe' affects the angle at which the cable enters the mech. I'm not sure if that affects anything?

Any ideas welcome.

gozzy

Ditch the barrel adjuster and fit an inline maybe.

parkinpants

thanks, never seen those before but will try them out, seems daft buying a new mech just for that (if that even is the issue)

gloomyandy

Did you use a long enough loop of outer for the last section of cable run to the rear mech? This often has to be longer than "looks good", if the curve is too tight the cable can bind a little in it and this usually causes problems when going from large to small cogs.

Also if the barrel adjuster is that worn maybe other parts of the mech are as well (like the return spring).

Finally have you checked that the mech is aligned properly? Could the rear hanger be bent?

crankycrank

I'm not clear if you have any adjusters for your cable now. It may be just a case of not having a precise adjustment available due to your stripped adjuster threads. If no other adjusters, you can just screw a nut onto the mech adjuster barrel to make it functional again. The threads can be repaired as well if you have the tools and knowhow but depending on what make/model it is it may be cheaper to buy a new one if you have to pay a shop to fix the threads but as I mentioned a nut on the adjuster will work. You usually need a only a 1/16 or 1/8 turn to get it just right for both up and down shifts. In addition to gloomyandy's suggestions some more things to check. Possible frayed cable, housing ends not cut cleanly, worn cogs and chain (when both are worn shifting tends to hesitate), loose chainring bolts, B-tension screw needs adjustment, rear mech pivots need cleaning/lube, double check your cable routing through all the guides.

parkinpants

thanks for all the suggestions...

Yes, I still have two barrel adjusters (one on the underside of the frame, one on the shifter)

I think the outer is a decent length. It's been that length for 2 years and always been fine before. However, the missing barrel adjuster does make it curve too tight in my opinion, so I'll see if these 'inline' adjusters help it to stay in place.

The rear mech is nothing special. It's just a Tiagra, and it's 2 years old now along with the chain and cassette. I'm not sure what mileage I should expect but it's done over 2000 miles (yes same chain).

I'll try the inline adjusters first and then take it from there.

gozzy

If you've got a barrel adjuster on the shifter then there's no need for an inline one, the one on the shifter will do the job. You only need one adjuster for each mech.

arlowood

I would suggest that the main problem you face is that stripped thread for the rear mech barrel adjuster. As you state it is causing problems with the cable and outer routing at the rear mech itself.

IMHO that final barrel adjuster point is crucial to give you a stable basis for adjusting the cable tension and fine tuning the indexing. After all most mech/indexing set-up videos rely on that barrel adjuster to pre-set the right tension when doing any basic indexing. Even with the existence of adjusters at the shifter and elsewhere, you may still struggle with the fine tuning if the cable and outer can move around on the rear mech.

If I were you I'd bite the bullet and replace the rear mech - a Tiagra one will only cost you £22 and will save you endless faffing about

http://www.chainreactioncycles.com/shim ... lsrc=aw.ds

or keep a close watch on the classifieds

darkhairedlord

Probably the cold weather. The normally fluid mix oil, water, grease, wear debris etc tends to dry up and harden off, this in combination with a stiffening of cable outers and liners prevents the cable releasing as quickly as normal. Same problem at the pivots in the rear derraileur.