Chain ring BCD

The Rookie
The Rookie Posts: 27,816
edited March 2012 in Workshop
Hi all, first post in the road section, so please be gentle...

The daughter has just brought her MTB back from Uni and taken her commuter, however due to the steep hills (Aberystwyth) she is struggling on gearing, she has an 11-28 Cassette out back which is the largest ring size the 105 rear mech will cope with, so we want to drop her small ring at the front, it is a Truvative Elita crankset (ISIS) taken we believe from a Boardman and is running a 32T inner (+42T/53T) on 5 arm, she is trying to measure the BCD (when you wish it was 4 arm!) but anyone any idea what it's LIKELY to be (outer BCD is 130mm) so we can compare measurements to it please?

Simon
Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

Comments

  • nicklouse
    nicklouse Posts: 50,673
    guess what i will say?

    sheldon has a great way to measure it.

    http://www.sheldonbrown.com/gloss_bo-z.html#bcd

    and a crib sheet.

    should be 74mm
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jomoj
    jomoj Posts: 777
    pretty sure it will be 74mm, standard for road triples
  • The Rookie
    The Rookie Posts: 27,816
    Was sure it would be 74mm, but thanks for that link Nick, hadn't thought of doing it that way (pretty stupid of me!)

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • John.T
    John.T Posts: 3,698
    http://www.spacycles.co.uk/products.php?plid=m2b0s149p290
    Any of these down to at least the 26 will work fine. 24 may but I don't know anyone using it so can't say for sure.
    My Fleet.
  • The Rookie
    The Rookie Posts: 27,816
    Thanks for the link John, good prices!

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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