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Gear changing issues

robthehungrymonkeyrobthehungrymonkey Posts: 616
edited March 2009 in Workshop
I appreciate that this is probably an obvious newbie question... :oops:

I have recently started getting problems with the rear trying to change gears by itself, which is annoying as it's always at a bad time!

There seems to be two particular gears that it does it on, the biggest cog (i think, might be the 2nd) which changes down and then returns to the original cog more often than not. This is especially annoying as it always happens under power on steeeep bits when momentum is important!
It also happens on the 2nd smallest cog, but generally jumps and stays on the smallest cog. Not as annoying, but not ideal.

This all worse, as at the weekend i'm doing my first charity ride (that I can't miss as my Girlfriend's Dad is organising it).

Any help would be great. - Design-Led home furniture and accessories.


  • John.TJohn.T Posts: 3,698
    Check the indexing. It sounds as if the cable has stretched a little.
  • The cable had stretched a few weeks ago, and after adjusting it, seemed to work ok.

    The symptoms then were that it wouldn't go to the bigger cog, this is different. Could it still be the same problem? - Design-Led home furniture and accessories.
  • John.TJohn.T Posts: 3,698
    It could. From your description it sounds as if the chain is slightly out of line with the cog and is trying to change gear. Try tightening the cable 1/4 turn at a time.
  • kozzokozzo Posts: 182
    Did you check hanger?
    Possibly it is misaligned.

    It is almost automatic gearbox :wink:
  • kozzo wrote:
    Did you check hanger?
    Possibly it is misaligned.

    It is almost automatic gearbox :wink:

    Yeah, maybe an early Rover auto or something. Always changing gear when you don't want it to!

    How would I go about checking the hanger? :oops: - Design-Led home furniture and accessories.
  • kozzokozzo Posts: 182
    In LBS
    Special tool is required.

    I had case like this just after crash;
    hanger was touched and with different force of pedaling
    I had jumping gears

    Look at this explanation
  • censored ,

    Can't really afford an LBS trip at the mo. (time, [if you work 9-5 it's impossible to get anything done!] and money).

    I haven't ever crashed my bike, but maybe it's been knocked or something. I'll check that when I get home. - Design-Led home furniture and accessories.
  • John.TJohn.T Posts: 3,698
    Always check the easy things first. It is usually one of them anyway. Faults on bikes tend to occur firstly due to things going out of adjustment, then things wearing out. Crash damage and faulty parts are some way down the line. Unless you fall off a lot.
  • andrewjosephandrewjoseph Posts: 2,165
    Put the bike in a stand (or upside down if no stand), change to second highest gear (second smallest cog on the back) whilst turning pedals.

    turn the barrel adjuster until the chain is starting to change up to the next bigger cog, reverse adjustment until the chain is running quietly. Check everything by shifting up and down the cassette.
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • thanks for all the replies....

    Will got on it tonight. - Design-Led home furniture and accessories.
  • Meds1962Meds1962 Posts: 391
    While you're doing it, make sure that the cable is running freely in the small section of cable outer at the mech end and at the guide under the bottom bracket.
    O na bawn i fel LA
  • I gave the bike a clean and a lube last night but it turned into a complete mission! (lots of hard, not budging dirt!). So didn't actually have a chance to go for a test ride.

    The hanger might have been very slightly bent, but it was hard to tell, i kind of tried to push it the other way a bit. Will see if it made a difference later.

    Thanks - Design-Led home furniture and accessories.
  • AndyOgyAndyOgy Posts: 579
    Rob - I just noticed that you're in East Sussex. Don't suppose you're anywhere near Brighton/Hove at all are you?
    Reason I ask is that I've recently been using a bike repair company called South Coast Bikes. They are a top notch repair company who come and pick up your bike in the evening and return it the following evening. I've called them at 9pm before now. But they have the jig for sorting out a bent hanger and they recently fixed a problem with my gears jumping. They fixed that, trued my wheels, replaced rear brake pads, cleaned/lubed the whole bike and it all came to a little over £30 for labour (plus the brake pads).

    Here's the link to their site:
  • Thanks for that Andy,

    I'm just north of Lewes, so it's not too far. Last summer I paid £65 for a service at my LBS, which was pretty much exactly what you got for £30!

    I think I'll contact them if the problem persists. - Design-Led home furniture and accessories.
  • AndyOgyAndyOgy Posts: 579
    I've been really impressed with them so far. I have a stable of 3 bikes that are all currently running sweet as a nut thanks to those guys. They recently rebuilt my 20 year old Trek and it now runs like new. It didn't even run like new when it was new.
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