what size BB to fit a chain guide?

swampi101
swampi101 Posts: 210
edited September 2009 in MTB workshop & tech
Hi all,

I currently run a single ring with bash up front, and the chain has a tendency to slip off when changing gears. I want to fit a chain guide to keep it on but since I dont have ISCG mounts it will have to be BB mounted, and thats where Im stuck.

I think I know what chain guide I want but Im unsure of what size BB to get so it will fit with no problems. my current BB is 68mm wide with 113mm axle. would I need a 73mm wide BB or does that stay the same? Im confused as to whether the axle length or BB width changes :?

Comments

  • nicklouse
    nicklouse Posts: 50,673
    what is your current BB?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • swampi101
    swampi101 Posts: 210
    RPM Power Pro, ISIS drive
  • nicklouse
    nicklouse Posts: 50,673
    just remove one spacer from the drive side.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • swampi101
    swampi101 Posts: 210
    there isnt a spacer :?
  • nicklouse
    nicklouse Posts: 50,673
    well most ISIS BBs come with 3 spacers allowing use with 68 and 73mm bb and with or without a bb mount mech/device.

    so really any will do Except yours.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • swampi101
    swampi101 Posts: 210
    ok thanks Nick :)
  • swampi101
    swampi101 Posts: 210
    I just had an idea, Im probably not the first one to think of it but oh well.

    Stupid question but would using 2 bashguards work as a chainguide? i.e. get longer chainring bolts and put a bash on either side of the chainring. my bash seems quite close to the chain so im thinking it would actually keep the chain on without buying expensive guides. probably lighter too.

    EDIT: also though of using 2 old front derailleur mounts to fit a taco bash guard to, and then adjust it so it is level with the actual bash ring but on top... if you get what i mean. it would have to be within 1-2mm of the chain to work as a chainguide but i reckon it could work :)

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