new bike drivetrain issues

_joe_
_joe_ Posts: 8
edited April 2010 in MTB workshop & tech
right, i am just building up my new bike, and am having issues with clearances, parts fouling around the bottom bracket

The frame is a 2003 rocky mountain switch, and i am running a truvative box guide, a 68/73x118 truvative dh bottom bracket, and husselfelt crank arms.

the first issue, is that with the boxguide inplace, the drive side crank cant be bolted up or turn as the granny ring bolts foul on the boxguide adjustment bolts,

the second issue is on the non-drive side (and possibly the drive side) the pedal end of the crank arm is fouling on the chainstay.


my first thought is to grind off the granny ring bolt holes on the crank arm, so that it clears the boxguide, but this wont solve the chainstay issue, would this all be solved by running a bottom bracket with a 128 spindle?

any help appreciated.

Comments

  • supersonic
    supersonic Posts: 82,708
    A longer axle would help yes: what chainline have you got, and what is recommended?

    Many people file the tabs down too.
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • peter413
    peter413 Posts: 5,120
    You need an e-type BB if you aren't using ISCG mounts on the frame
    Transition Patrol
    Cube LTD 29er

    Glentress Trailfairies
  • _joe_
    _joe_ Posts: 8
    an e-type bottom bracket? i am using an e-type chain device as it has no iscg tabs.

    i am not sure what chainline i have, will the longer axle stop the crank arm fouling on the chainstay?
  • _joe_
    _joe_ Posts: 8
    right looking into what i have got, i am running an e type bottom bracket, which is fine.
  • nicklouse
    nicklouse Posts: 50,675
    we are talking ISIS BB here?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • nicklouse
    nicklouse Posts: 50,675
    118mm axle should give you a 51mm chain line.

    so BB mount box guide. the 3 bolts on the device remove the washers does that help.

    if not then you will have to look at a longer axle or a different device.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • _joe_
    _joe_ Posts: 8
    yeh its isis drive. i thought about using the boxguide mounts in the other direction, but that didnt work. ill grind of the tabs on the crank tomorrow at uni as i wont be using them, and ill get another bottom bracket i suppose, the extra 5mm each side should make it clear the chainstays and the chain device tabs should it not?
  • nicklouse
    nicklouse Posts: 50,675
    but you may find the chain line crap in the big rear cogs.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • _joe_
    _joe_ Posts: 8
    thats true, can you think of any other way around the issue?
  • nicklouse
    nicklouse Posts: 50,675
    ok first forget the device bolts catching and see if the arm can be fully tightened. then if yes measure the overlap. how much do you need to lose where...

    in other words what do you need to do to get the current parts to work (maybe they will not)

    so measure your front ring chain line. if it is OK then what do you need to grind.... will it work or fall apart. if fall apart new bits will be needed.



    it will/could take time and parts to get it sorted. start of with getting the parts fitted correctly but maybe not working. then you can see what needs to go...

    hard to put in words but easy to see when working on it.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • _joe_
    _joe_ Posts: 8
    yeh i see where your coming from and it all makes sense,

    when i tighten up the crank arm, there is a 2mm overlap with the chainstay, so this issue should be solved by the bottom bracket spindle length change, but obviously this would affect the chainline, what is the best way of measuring my chainline?

    All that would need to be filed/ground off would be the protruding granny ring tabs on the drive side crank arm, the only reason i suggest this is that i have seen it used before.
  • nicklouse
    nicklouse Posts: 50,675
    well the config you have now should give the correct chainline. so if grinding will fix it do it.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • *AJ*
    *AJ* Posts: 1,080
    Could you not use a washer between the chain ring and the spider to adjust the chainline back in slightly? assuming this does not make your chainring foul your device.
  • nicklouse
    nicklouse Posts: 50,675
    yes you could. chain ring washers are about 70p each.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • _joe_
    _joe_ Posts: 8
    right, the correct length bottom brakcet is now in, and i used a grinder to get rid of the tabs on the crank arm. i now have no fouling issues which is nice.

    the issue i have now is that even when the bolts on the cranks are done up as tight as possible there is play in the crank arms.

Categories