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Gear changes

dormer88dormer88 Posts: 109
edited September 2012 in Road beginners
Having had my bike about a month now. The gear changes dont seem to be as fluid as they once were?

Could this be a number of reasons or a simple fix?

Posts

  • ProssPross Posts: 25,424
    Cable stretch possibly? Or possibly the cables are dirty.
  • dormer88dormer88 Posts: 109
    That as simple as a general clean? Which of the cables would need tightening? They dont look slack but must admit never paid a massive amount of attention to it
  • ShutUpLegsShutUpLegs Posts: 3,522
    dormer88 wrote:
    That as simple as a general clean? Which of the cables would need tightening? They dont look slack but must admit never paid a massive amount of attention to it

    The cable that goes to the rear gear changer thingy
  • Mikey23Mikey23 Posts: 5,306
    Cable stretch I would assume. My bike shop did a free service on mine after 100 miles for this reason and showed me how to do it thereafter
  • dormer88dormer88 Posts: 109
    Cheers guys! Will pop in to my LBS and get them to have a look
  • ProssPross Posts: 25,424
    dormer88 wrote:
    That as simple as a general clean? Which of the cables would need tightening? They dont look slack but must admit never paid a massive amount of attention to it

    Start off with the tension. There should be a barrel adjuster where the cable enters the rear mech
    . Simply turn that (by hand) anti-clockwise a quarter turn at a time. This should make the cable tighter and the gear changes crisper. If the gears start jumping you have adjusted too far. The cable stretch would be tiny so not something that would be apparent to the eye.

    To clean the cable simply remove the rear inner cable from the outer on the section near the rear mech, wipe the entire inner cable with degreaser and (assuming the inner cable isn't plastic coated) apply grease and rub it in.

    EDIT Stretch is the most likely cause and look at that first, even pretensioned cables can stretch a bit. It's still worth knowing how to clean / lubricate the cable though as this should be part of your regular maintenance.
  • dormer88dormer88 Posts: 109
    Cheers Pross, have given it a tweak. Will give it a go in the morning at report back.
  • dormer88dormer88 Posts: 109
    Hi guys, went out an tried it today! Felt no better so tweaked it abit more it's now jumping and won't move up
    Into the higher gears! I have tried to loosen the cable as much as possible and move it back through but the cable length seems to have got smaller and won't return to its original length past the bolt I turned!
  • rsandsrsands Posts: 60
    you need to start from scratch and set your high and low end screws first. can the bike get into both high and low gears?
  • thescouselanderthescouselander Posts: 549
    edited September 2012
    I think you might have overdone it - you'll need to start again. Screw the barrel adjuster all the way in (clockwise) and change into the smallest/highest gear at the back - give the leaver a few extra taps to be sure its at the end of its travel. Next give the gears two taps so you should be on the third smallest/highest gear at the back and give the pedals a few turns. At this point the chain might be on the second smallest gear so you will need to turn the barrel adjuster a bit at a time until it changes to the correct gear - once its there its just a matter of fine tuning.

    If the bike previously went into the highest and lowest gears I'd leave the limit screws until you've tried the above.
  • dormer88dormer88 Posts: 109
    Il give it a go cheers! So the chain should be at the top
    Ring at the back? Currently when I try to change to a higher gear it goes down to the smallest ring
  • dormer88 wrote:
    Il give it a go cheers! So the chain should be at the top
    Ring at the back? Currently when I try to change to a higher gear it goes down to the smallest ring


    The highest gear = the smallest one at the back.
  • dormer88dormer88 Posts: 109
    Have tightened it up moved the gear to the lowest clicked it in twice but It doesn't move off the smallest ring! Tried loosening the bolt but still no movement!
  • dormer88dormer88 Posts: 109
    Can no get it to the 3rd ring from the top?
  • Sounds like the cable has slipped. If you keep changing up (towards the smallest cog) does the cable go slack?
  • ProssPross Posts: 25,424
    What is the position of the barrel adjuster now? Is it still screwed in nearly as far as it goes? If so just put the lever back over to its limit again as if trying to move it on to the smallest sprocket (highest gear) and then go back two clicks again. Then keep unscrewing it until it does eventually jump onto that 3rd smallest sprocket. It should go as it did previously unless you have slackened off the cable by undoing the actual bolt that connects the cable to the mech (if that is the case loosen the bolt again pull the cable tight whilst re- tightening and then go back to using the barrel adjuster). Once it is on the 3rd smallest sprocket fine tune with quarter turns. If the gears jump up onto a bigger sprocket then the cable is too tight so turn the barrel adjuster slightly clockwise, if it won't move onto a bigger sprocket when selected the cable is too slack and turn the adjuster anti-clockwise. Google Sheldon Brown gear adjustment for a better description with pictures.

    BTW 'higher gear' means a smaller sprocket on the cassette and the larger front chainring (i.e. harder) 'lower gear' is smaller chainring / larger sprocket. Basically the bigger the difference between the number of teeth on the front chainring and the number of teeth on the rear cassette the bigger the gear. It will be harder to turn the pedals but you will go further for each pedal turn and therefore faster at the same pedalling rate.
  • dormer88dormer88 Posts: 109
    Jee, thanks for the help guys but all that has gone way over my head! To the LBS for another waste of £30 as I really don't know what I'm doing! Cheers though many thanks
  • CiBCiB Posts: 6,098
    rsands wrote:
    you need to start from scratch and set your high and low end screws first. can the bike get into both high and low gears?
    No. No. Just no. You haven't changed anyything that would require the limit screws to be adjusted. Leave these alone, unless you're very confident that you know what you're doing and why.

    Undo the clamp on the mech that holds the cable in place and spin the pedals to turn the gears - the chain should sit nicely in top gear. Drop some oil down the outer cable and along the inner and slide it back & forth a bit till it has a nice smooth sliding action. Then grip the inner at its end with fingers or pliers and pull whilst moving the gear lever as if changing into top gear (smallest rear cog) so that you're sure the indexing in the lever is at the end stop.

    Now refit the cable to the mech, after adjusting the barrel adjuster and the rear mech cable adjuster to something around their mid points. Once it's all back together do coarse adjustments on the back and fine at the front (barrel) adjuster. £30 saved for a bit of thought & effort.
  • dormer88dormer88 Posts: 109
    CIB and PROSS! Thank you very much indeed! Done and dusted....hopefully!!
  • oldwelshmanoldwelshman Posts: 4,733
    ffs for something so easy seen some censored advice here. Lots of videos on you tube show how to do it.
    In a nutshell, change fron ger to be on largest chainring.
    Change gear on the back until on hardest gear.
    If it is set up already you can check the tension on the cable down the down tube (this is where the cable runs from the levers, under the bottom bracket area.
    the cable should not be very slack and should not be very tight (hope that makes sense)
    If it is very loose or very tight, just slacken the cable fixing bolt on the rear changer, adjust the barrel adjuster clockwise until fully in, and pull the cable to be finger tight before re fixing the cable.
    The quick way to check the limit screws is to turn pedals (hope the bike is in a bike stand) and pull the rear changer cable (by the down tube) with your hands and check that the gear can go all the saw to the big rear sprocket without going into the spoke :D if you cannot reach the large sprocket then the limit screw needs adjusting (I suspect it is ok as it worked before).
    When you release tension the chain should go back to smallest rear sprocket.
    Now you can adjust gears.
    Change up and check all gearsw are reachable, probably will not get to large sprocket or it may rattle and probably have to turn adjuster barrel one turn to increase tension.
    Shimano are easy to do and normally can do just but setting up cable fixing and one turn.
    After this set up, I usually sellect a mid gear, then adjust the barrel clockwise until gear change , then back counter clockwise until it changes two gears (count turns).
    Then I turn clockwise half the number of turns so this sest it in between so should be perfect.
    Hope this makes sense lolits easier to show someone than describe it.
  • CiBCiB Posts: 6,098
    I think we need a sticky that says simply "do not attempt to resolve gear change issues by starting with the limit screws. Please do not suggest it as a means of resolving gear problems".

    The potential for damage is huge if you get it wrong. If someone's asking how to do the equivalent of tying your shoelaces, knowledge of limit screws and the implications is likely to be on the low side so starting by fiddling with limit screws is a bad idea.

    In this scenario the gear change had become sluggish overtime. Nothing had changed that warrants screw adjustment.

    </grumble>.
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