Forum home Mountain biking forum MTB workshop & tech

drivetrain problem

andy83andy83 Posts: 1,557
edited June 2008 in MTB workshop & tech
was riding to work this morning and realised the chain was rubbing a little on the front derailler

when i got to work checked the limit screws but they were fine adn then realised that as i turned the pedals the chain seemed fine one part but then moved over and was rubbing on the derailler.easiest way to describe is when left pedal is nearer the front wheel it is fine for half a turn until it gets nearer the back wheel when it starts to rub on the derailler for half the turn. havent had much time to check but on way home could hear a creak and it seems like its coming from the actual pedal but cant actual tell whether its that or from the crank area. unfortunately havent got access to my workstand til tomo to put the bike in and test it properly

when i got back from work i leant against the wall and pedaled backwards and it felt that half way round it seemed like the whole crank seemed to jolt and then continue. other problem is i cant see any noticable movement from the crank coming away from the bb or frame just that the chain seems to be moving across. could it be somethig from the rear end of the bike and im just dismissing it

now the thing is dont think its the pedals due to the chain moving, and i put the bike together myself and have done maximum 40 miles since it has been rebuilt

is it a case of stripping the chainrings and cranks off and putting them all back on tighter, or should i take it to the lbs and just bite the bullet and let them sort it out. feel fairly confident taking it apart and putting it back together or could it be that summin is bent?

thanks in advance

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Sometimes the chainrings can run very slightly off centre. The creak could be something else entirely, finding it is a process of elimination.

    Try adding a quarter of a turn of tension to the cable.
  • andy83andy83 Posts: 1,557
    cheers for that

    did seem a lot worse after i adjusted the screws today

    the pedals are just cheap wellgo ones and personally think they have gone as can see rust around the bearings allready lol

    as i say cant see any visibile movement from the chainrings but the chain is moving, just concern me a little when i was peddling backwards and seemed like it was shifting, kind of moving at one stage like it was

    i know that new bikes have a 2 week service just to readjust the gears etc, could it be a case that this is what i need to do as all the parts are brand new and spose they have been given time to bed in now. rode like a dream at the start, but seems to have slowly started to rub, surely if the crank was lose i waould be able to see movement?? i grabbed the cranks and put a fair amount of forsce on and there was no movement whatsoever or creaking when i was doing this, only creaks when i put pressure down on the pedal in a certain direction
  • supersonicsupersonic Posts: 82,708 Lives Here
    yep, parts bed in, cables settle - often everything needs a readjustment!
  • skylinerskyliner Posts: 613
    Try tightening your chainring bolts and crankbolts unless you've got HTII cranks. Then you'll need to check the torque on the pinchbolts.
    The jolt you feel sounds to me like the crankarm is loose and if so, may be irreparably damaged. But try tightening it first.
    It's nice to be important, but it's more important to be nice.
  • andy83andy83 Posts: 1,557
    http://www.pinkbike.com/photo/2079041/

    that is a picture of my chainrings. as i say when i tried to move the crankarms side to side etc to see if there was any movement it just wouldnt budge at all. hopefully it hasnt caused too much damage if the crank arm is loose, only rode 3 miles tops with it rubbing. cant find mine 8mm allan key or octalink crank removal so need to go and buy them again.

    also havent got any torque wrenches so do you think that it is best to just take it to the lbs and get them to give it a good once over? just pay a service charge then they can just tighten everything up and check for any play in parts etc.

    the jolt is hard to explain but doesnt seem like the crank arms actually move just a weird feeling and once again not sure its the crank arms cos when i dont the same action just holding the crank arms didnt feel no jolt but but the chain still seemed to shift

    would it be likely i have bust the crank arms after only a few miles??
  • andy83andy83 Posts: 1,557
    tried to take some pictures to explain what i am trying to say lol, tried to include the crank arms to help explanaition

    this is when the chain rubs

    http://www.pinkbike.com/photo/2092519/

    http://www.pinkbike.com/photo/2092525/

    and this is when it doesnt

    http://www.pinkbike.com/photo/2092527/

    http://www.pinkbike.com/photo/2092521/

    thanks for looking people

    think i will just take it the lbs though as aint a lot of time and really need it next week, just want to know if it looks like a adjustment problem or my cranks are knackered

    cheers
  • andy83andy83 Posts: 1,557
    anyone any ideas before i take it the lbs??
  • x-islex-isle Posts: 794
    Hmm, it looks like maybe the chainring is bent? When the pedals turn, if you look down on the top of the chainrings, do they look warped?
    Craig Rogers
  • andy83andy83 Posts: 1,557
    na they are brand new

    have took it to the lbs to be serviced and they said they will sort out my discs which are a bit bent and strip the bottom bracket and chainset to give it a good once over, thought it best as all the cables need adjusting

    was a little worried that someone had knocked it at work but it doesnt seem bent at all, anyhow hopefully all should be ok when i pick it back up monday.

    bloke in shop said its very unlikely to be a damaged crank or bottom bracket, prob just needs a good once over
  • supersonicsupersonic Posts: 82,708 Lives Here
    Does it only happen when pedalling hard (ie not itn the stand?). Cranks and frames do flex slightly, often enough to cause this.
  • andy83andy83 Posts: 1,557
    yea thats what the bloke in the bike shop said, might not be able to get the creaking gone might just have to put up with it, only creaks when oi pedal, i am a 16 stone bloke lol

    anyway they are gona sort out the disc and give it all a good clean, including taking bb out etc which i aint got time today as working weekend so can pick it up monday so dont mind this once, feel bad though i learnt how to do it all myself now paying someone lol
  • andy83andy83 Posts: 1,557
    ok i have took it to the lbs and got it back, however the creaking is worse but bb all tightened and crank and pedals tightened. there is no play or movement of the crank which is a positive but the noise is worse, also quite annoyed they aint set the gears properly, can do it myself but i have paid for serivce

    should i take it back and get them to redo the gears and check the pedals

    the pedals are only cheap wellgo £10 jobbies, could it be they are knackered after only a few weeks, im a 16stone lad so bit of weight going on. do i need new pedals asap or will they be ok til the end of month due to lack of funds. could it damage the crankarm if i continue, its on the left hand side crank

    thanks in advance
  • andy83andy83 Posts: 1,557
    so anyone know if i need new pedals, forgot to say it does look like there is a little rust on the pedal where it goes into the crank arm

    decided im going to take back to the shop anyway as why should i adjust the gears when i paid for a service lol
Sign In or Register to comment.