Converting ultegra cassette from 11 to 12-28?

siddy1972
siddy1972 Posts: 180
edited January 2015 in Workshop
Hi all,
Given that ultegra10 speed doesn't come in 12-27 flavour, I was wondering if it was possible to convert my 11-28 to a 12-28 by buying another cassette (say 12-25) and dropping the existing 11 & 12 tooth and replacing it with the 16 and the 12 from the new cassette? Seems like it should work, or am I missing something...
Thanks

Comments

  • markhewitt1978
    markhewitt1978 Posts: 7,614
    I've looked into this in detail before and as far as I could tell yes, it would work, as long as the transition between the two cassettes takes place at the same ratio it would have been switching between if you see what I mean?

    However I decided it was too much effort and bought a 12-30.
  • siddy1972
    siddy1972 Posts: 180
    Thanks for the reply. The real driver behind this plan is to eliminate the 15 17 jump that I hate. I never spin out the 11, so I figured swapping the mostly redundant 11 for a 16 was the best answer. Hence a 12-30 wouldn't really solve the problem...
  • keef66
    keef66 Posts: 13,123
    siddy1972 wrote:
    Thanks for the reply. The real driver behind this plan is to eliminate the 15 17 jump that I hate. I never spin out the 11, so I figured swapping the mostly redundant 11 for a 16 was the best answer. Hence a 12-30 wouldn't really solve the problem...

    There's a 105 10 speed cassette (5700 series) that does 12-27, which according to Shimano Tech Docs includes the magic 16T sprocket. Might be a gram or two heavier than Ultegra but it's probably the easiest way of getting the sweet spot you're after.

    I know this since I have one in a box in the garage. Wiggle also claim to have them in stock...
  • markhewitt1978
    markhewitt1978 Posts: 7,614
    Here's the comparison I did last year

    11-28 11-12-13-14-15-17-19-21-24-28
    12-25 12-13-14-15-16-17-19-21-23-25

    Take the 12-25 cassete and put the 21-24-28 from the 11-28 onto it (those three are fixed together anyway)

    That gives you
    12-28 12-13-14-15-16-17-19-21-24-28

    The key point is that the transition between the two cassettes is at the 19-21 point same as it is on the original configurations, which (correct me if I'm wrong) means the pickups etc should all be still in the right places.
  • siddy1972
    siddy1972 Posts: 180
    Oh yeah, hadn't thought if it that way...much easier method to get what I wanted. Can't work out why Shimano dropped the12-27 in Ultegra but kept it in 105 and DA?
  • markhewitt1978
    markhewitt1978 Posts: 7,614
    siddy1972 wrote:
    Oh yeah, hadn't thought if it that way...much easier method to get what I wanted. Can't work out why Shimano dropped the12-27 in Ultegra but kept it in 105 and DA?

    Or why 12-30 is available in Tiagra and Ultegra but not 105?

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