middlechain ring compatability

kieranb
kieranb Posts: 1,674
edited April 2009 in MTB workshop & tech
Hi, I have an old shimano hollowtech chainset, rings needed replacing so i bought some new FSA chainrings. I had checked the BCD beforehand and so was fitting them tonight, got the inner on ok, got the outer on ok but the middle ring wouldn't fit? The bit where the holes are for the bolts was too large(going inwards to the centre too much), if I measured the diameter of the circle formed by the inner edge of the metal it came to 88mm but the tabs or whatever they're called, on the spider need them to be 90mm apart.? Is this typical and if so, will shimano only do? then I had thought these were interchangeable once you got the BCD right (+ number of arms)

thanks.

Comments

  • nicklouse
    nicklouse Posts: 50,673
    time to get the file out.

    shimano keep changing the diameter of the shoulders. while others crank makers use the same size for both.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown

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