Compact rings on a standard 105 crankset

h14turbo Posts: 329
edited July 2009 in Workshop
I have a standard shimano 105 crankset running 53/39, could I simply buy compact chainrings and fit them to the original crankset? Also, could I only replace the inner chainring with a 34 or so? Will that create shifting problems?



  • redddraggon
    redddraggon Posts: 10,862
    110mm BCD rings won't fit on a 130mm BCD chainset
    I like bikes...

  • k-dog
    k-dog Posts: 1,652
    Yeah, 2 problems - the rings are different sizes so they don't fit - a compact chainset has a smaller spider so needs a smaller 'bolt circle diameter'. And 53/34 is too big a difference for your derailleur to cope - it would also leave big holes in your ratios.

    50/34 is a decent compromise - you don't lose much at the top but gain lower gears for climbing.
    I'm left handed, if that matters.
  • Wappygixer
    Wappygixer Posts: 1,396
    The smallest ring you can fit to your 39/53 is a 38 if my memory serves me right so getting a 34 on is a no go.
    Just buy a new crankset and sell you old one