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Front derauileaur

Discussion in 'Bicycle Mechanics and Repairs' started by zummerzet_lou, 26 Feb 2008.

  1. zummerzet_lou

    zummerzet_lou New Member

    Location:
    Christchurch, UK
    Hiya,

    Am completely useless at adjusting my gears so hope you can help.

    I have a specialised sirrus 2007 .... and the front deraileur (sp?) is rubbing against the chain. Have attempted to adjust using the high and low screws to move it across I can either stop it rubbing, but doesn't go up to the top chainring, or it rubs.

    Is this easily fixed, or would it be better to just pop it into the LBS?

    Lou
     
  2. simonali

    simonali Über Member

    Location:
    Wiltshire
    Have you tried twiddling the cable tensioner thingy on the shifter? That might tune it out.
     
  3. OP
    OP
    zummerzet_lou

    zummerzet_lou New Member

    Location:
    Christchurch, UK
    Yep . didn't seem to make any difference what so ever

    I should also add that I use my bike daily, but not really cared for. I KNOW I should take more care of it, but dark winter nights don't inspire me to clean, oil etc.

    I did initially think the scraping noise was grit in the chain, so have cleaned the chain, and gearing as best I can with a sponge, brush and hot soapy water but if definately needs a good clean - muc-off or something similar?
     
  4. frog

    frog Guest

    My old favourite. Bikes rides all OK and fine then all of a sudden you're having trouble getting the chain to move over to the outer (large) ring. If you adjust you get it on the outer ring ok but then it won't change down to the inner ring :tongue:

    You need a new chain. To change gears the derailluers rely on a certain amount of side to side regidity in the chain to deflect it from one ring to another. When it gets worn instead of deflecting with the cage it runs smoothly around it, and missing the jump onto the next ring.

    Change the chain now and that will save you some wear on the rings and cassette into the bargin.
     
  5. OP
    OP
    zummerzet_lou

    zummerzet_lou New Member

    Location:
    Christchurch, UK
    Is there any way to adjust it just to ride 8 miles Wed and Thur as I need to get to work?

    It's probably due a new chain ... but what should I adjust to try and stop it rubbing on the front derailer?
     
  6. domtyler

    domtyler Über Member

    Take it to the bike shop and get it cleaned up and serviced. It has looked after you all winter, now it's your turn to look after it.
     
  7. Paulus

    Paulus Getting older by the minute

    Location:
    Barnet,
    If it wont go onto the large chainring, even though you have adjusted the limit screws, the problem could be the cable tension. It is not tight enough.The cable may of stretched and there is not enough tension in it to move it sufficently on to the chainring. Move the chain onto the smallest chainring so that the cable is at it's slackest, adust the adjusters so they are at right in, then undo the cable clamp nut on the front mech and pull the cable until it is taught. Do up the nut and try again adjsting the cable as neccesary.
     
  8. frog

    frog Guest

    Depends on what sort of adjustment you have. If it's something like a Shimano Sora all you have is two limit stops at either end of the swing in and out. All other adjustment is done by shorting/lengthening the actual cable where it attaches to the changer.

    You should only get the scraping when you have tried to change to another ring and the change hasn't happened because of what I mentioned above. Selecting back to the ring you came from should stop the sound.

    If you still have scraping noises then it might because you are in the wrong gear on the cogs at the back and changing up or down a gear might lessen the noise.

    From what I remember of the problem you will loose the larger outer ring, all you get is no change up and a scraping noise. You should still be able to change down to the middle and inner rings. If you have scraping then it might well be because you are on the smaller cogs at the back. Changing down will lessen the racket.

    As a quick and dirty set up I'd put the chain on the smallest ring and biggest cog and adust the inner limit screw until it goes quite. Try the rear gears up to about 5 or 6 and you should start to get some rubbing on the other side of the front cage. Move the chain onto the middle ring and then you should be able to all the way down and up on the rear cogs. If not it might mean you have to limit yourself to staying off the largest and smallest cogs at the back. That will be the range of your gears until you get the chain sorted and the outer stop positioned correctly.

    So, essentially, you loose the outer ring and the top three or four gears and possibly one of the lower ones as well.

    Forget about using the outer ring until the lbs have given it a going over
     
  9. OP
    OP
    zummerzet_lou

    zummerzet_lou New Member

    Location:
    Christchurch, UK
    thanks .. will put all your advise into action this evening .. did try LBS but they are snowed under with bikes.

    All gears work, and I can change freely between all of them, tis jut the noise I'm trying to elliminate .. will see if it's OK on the middle front cog, and a combination of rear ones just to get me to work .... and I may have to get the park tools website up at the weekend and strip and service it myself as it's long overdue.
     
  10. Monkey Boy

    Monkey Boy New Member

    If you don't switch from big to small ring very often then the front mech can seize up.....like mine has done! Try spraying with WD40 and give it a good 'wiggle' over the next few days to see if she'll free up a bit.
     
  11. 02GF74

    02GF74 Über Member

    you donlt say if you have 2 or 3 rings at the fornt.

    probably repeating as what hasd been said already.

    There are two end stops on the derailleuer that limit total travel.

    The cable tension pulls the chain onto the big ring so if you cannot do that then either the top stop is screwed in to far or t here is not enough cablke tension.

    Cable tension is adjusted by a round ferrule on the shifter (I am assuming mountin bike) but road STI have similar arrangement on down tube.

    If there is too much cable tension,then the chain cannot be dropped onto the smaller ring.

    So it is a matter of setting the end stops first so the chaing does not pop off eitehr ring, then set the tension.

    3 chain ring shifters have an itermediate posiiton for the middle ring and this is set soley by cable tension.

    If you can use a screwdriver and a hex allen key, there is no need to seek anyone else';s help, let alone pauy for it.

    I have found that eventually the small wires making up the cable break, almost always at the derailleur screw and this affects tension so the symptoms of chain rub as you describe occur.

    phew, I;m really tired after typing all that out.
     
  12. OP
    OP
    zummerzet_lou

    zummerzet_lou New Member

    Location:
    Christchurch, UK
    Thanks everyone .. I now have something that is usable for Weds and Thurs commutes.

    Thinnking about it, I have been having gradual problems for a while, and just put it down to not evough lube.

    It's a sirrus comp, with a triple at the front .. and although I can select each of the 3 chainrings, at the extremes seems to be when the chain rubs the chainguide - at least I know what to avoid now.

    Think it might be time for a new chain, and definately a strip down and thorough de-grime!

    Bike is getting packed ready for it's emigration to NZ in a couple of weeks or so, so might put the serious service till after it's arrival (and we are settled in to where-ever) and just keep her going for the time being .. I WILL be back!! ;)

    Lou
     
  13. simonali

    simonali Über Member

    Location:
    Wiltshire
    Fiind out if bike parts are cheaper over there or not. Might cost you more cash!
     
  14. 02GF74

    02GF74 Über Member

    Now it may have already been said but when you get the cahin rub, what gears are you in?

    although you have 7/8/9/10* gears on the cassette, you should not and in some set ups cannot select all of them with each of the chain rings at the front.

    The middle ring should be usable with all of them but the outer ring (biggest) with the smaller ones whilst the smallet inner ring with the biggest sprockets.

    So there may not be a problem after all.?

    * delete as applicable.
     
  15. bonj2

    bonj2 Guest

    this should be all you need to know, it details the procedures step by step.
    http://www.parktool.com/repair/readhowto.asp?id=75

    It's important to start from scratch and do everything in order, rather than to assume you can skip a certain step 'cos it 'should already be right'. it might not be!