Thoughts? Gears shifting down but not up at rear

OSOH

Hi, just wondered if anyone could help, I don't have a clue with anything technical but am hoping someone may have more of an idea of what's going on. Apologies if the terminology is wrong, but I hope I can give people an idea of what I mean!

I've got an old mountain bike with thumb shifters, push one way to move up through the gears, other way to move down. However it's not working that way!! I can't move up through the gears at the back, the shifter clicks but the chain remains on the largest cog. If I move the mech(?) by hand, I can move up through the gears that way, if I have tried with the shifter first; for example, 3 'upward' clicks of the shifter and I can manually move the mech/chain up 3 cogs, but the shifter won't do it by itself.

I'd appreciate any thoughts on what this may be, as it's annoying me. The bike is a Raleigh Activator 2, though guessing that won't be much help.

Thanks for reading!

festa2

Sounds like its cable related, Could just need a bit of tension if its a bit slack, turn the barrel adjuster on the shifter anti clockwise a few clicks at a time and see if it helps also the inner cable may need some lube to free it up..

oodboo

Replace the inner and outer cables. It's a fairly easy job and should only cost a couple of quid.

The Rookie

Check to see if the cable is still tight between the adjuster and end clamp at the rear mech, if it is, then it's cables, if not then it's the pivots and/or spring at the mech that need sorting.

Neal_

I had a similar problem with a new rear mech which had stiff pivots so the mech spring couldn't overcome the friction. Thoroughly clean and lube the rear mech and replace the inner and outer cables as it'll be friction causing the problem.

OSOH

Thanks for all replies. I've just re-read my original post, and realised it doesn't - apart from the title - mention that the gears will shift fine the other way (i.e. smaller to larger cogs) using the shifter, does this alter the advice that would be given as the problem only occurs going one way? I do have some cables which I could probably fit, but it would be a major task for me as I've not done it before (bike shop/mechanic isn't an option), so just wanted to make sure people still think it may be the cables.

Thanks again for people's suggestions, much appreciated!

steelie600

sounds just like a seized rear derailleur to me tbh. give it a bloody good clean and lube it up and work it by hand till its free.

oodboo

If it's going one way (against the spring in the deraileur), but not the other then it sounds like the cables are causing too much friction for the spring to overcome and change down to the smaller gears. New cables and clean your deraileur while you're at it.

OSOH

OK thanks, will have a go at derailleur then try cables then! Wasn't sure whether suspect would be derailleur, cables or shifter - from replies it seems it's been narrowed down, was really hoping it wasn't a shifter fault after problems with one previously!! Sounds like good news.

Thanks again, wasn't sure how serious this issue was likely to be but sounds like it'll be less major than I thought. I suspected either replacement derailleur or shifter...not worth it...but hopefully a much simpler solution!

nicklouse

Do the cables first. 99% of the time it will be the cables.

OSOH

I probably will end up doing the cables, but will have a go at the derailleur first as it'll be simpler, and if by some chance that does solve the problem then it'll save me a lengthy job doing the cables and fiddling around. Plus I need to find my spare cables before I can do anything!!

Thanks again for all suggestions, will post back when I've had a go at it.

nicklouse

Well as you should be removing the mech to clean it and I bet the cable will be nicely frayed...... Get cables before you start and do the cables is only a few minutes job.