Double > Compact

bigaac
bigaac Posts: 72
edited June 2014 in Workshop
Having grown less afraid of hills i'm starting to realise that my 53/39 crank (Shimano Ultegra 6700 10sp) are making life more difficult than necessary and i'm always finding myself looking for a lower gear on climbs.

Friends have suggested I make the change to compact, the question is how easy is it to do? can i just buy a new small chainring? or do i need a whole new crank? I'm assuming it doesn't affect the cassette or Di2 setup?

My current crank is Shimano Ultegra FC-6700 (53/39) http://www.chainreactioncycles.com/shim ... -prod39017

Thanks

Comments

  • wishitwasallflat
    wishitwasallflat Posts: 2,927
    You need a new crank cause the bolts that attach the chainrings to the drive side crank (spider) are different distances apart on double and compact - the BCD is what it's called. Any Shimano compact crank should slot straight in to the bottom bracket you have (Hollowtech 2) the only adjustment you would need would be to lower and re set your front mech. None of it is hard if you have the tools you need u-tube will have video guides on how to change crank sets galore - if you have any common sense and basic mechanical skills DIY it - if not ask a friend or an lbs you trust.
  • bigaac
    bigaac Posts: 72
    OK great, thanks.

    so this should do the job, my bottom bracket is the Shimano BB71

    http://www.chainreactioncycles.com/shim ... -prod39018
  • wishitwasallflat
    wishitwasallflat Posts: 2,927
    I'm not familiar with that BB but its listed as a press fit BB compatible with HT2 cranks and your link is to an HT2 crank and your old double was HT 2 so even without direct personal experience of that particular BB yes it will be fine 100% :!:

    If in doubt check out the second buyers review here

    http://www.chainreactioncycles.com/shim ... -prod61803
  • bigaac
    bigaac Posts: 72
    great thanks :)
  • mr_evil
    mr_evil Posts: 234
    Have you considered changing cassette instead? A 12-30 cassette is much cheaper than new cranks, and usually requires only minimal adjustments.
    https://mrevil.asvachin.eu/
  • bigaac
    bigaac Posts: 72
    Ok, so i've swapped the Double for an Ultegra 6750 50/34 (Currently £99 at Merlin BTW) and fitting was easy enough.

    Just a quick query though - the Chain is rubbing a little on the front derailleur when on the big and small ring of the rear cassette, which is odd as the rear cassette hasn't changed. The Di2 does adjust a little but seemingly not enough, is there any way to adjust how much Di2 adjusts the front derailleur?

    thanks all
  • bigaac
    bigaac Posts: 72
    Its amazing what you find on the internet AFTER you've posted a query on the forums :lol:

    http://www.youtube.com/watch?v=PU2kQp9IeBc

    Still though - i'm interested to hear peoples thoughts on why it would be rubbing all of a sudden

    thanks

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