Will Ultegra 8100 chainrings fit dura ace 9100 crankset?

Looking at “downsizing” for a hilly European trip, and this would seem the cheapest option, from Dura Ace 9100 chainset , to swap for Ultegra 8100 50-34 crankset. Are they interchangeable?

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  • daniel_b
    daniel_b Posts: 12,135
    edited January 27

    It's a little confusing, as in the subject you talk about chainrings, which suggests removing two chaingrings (52 & 36 presumably) and replacing with Ultegra chainrings, 50 & 34.


    But then in the text you are talking about chainset and crankset.


    If it's the latter, that will be a like for like swap, you would just have to adjust the position of your front derailleur, and potentially re-index it, although if it's Di2 that's a doddle.

    You might also need to shorten the chain, which would obviously be a pain as you will then want to revert once you are back.

    If you do need to shorten the chain, you would probably be better to buy a chain to use with the 50/34, and just keep it as a 'mountains set'


    If instead, you are asking about whether you can fit individual chainrings onto the 9100 52/36 crankset, that I am not sure about, as it's all to do with the BCD of the rings on there, versus the 50/34 ones.

    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • I think it may be the latter Dan, can the Ultegra chainrings be swapped on to a DA crankset. My understanding is that they cannot, even though it is the four arm design. I have read examples of people trying this across various Shimano 11 and 12 speed variations and the feedback is usually that they are not compatible. I can't say 100% how accurate this is though as I have never tried it myself.

  • super_davo
    super_davo Posts: 1,250

    I have used 105 chainrings on Ultegra and vice versa, and they worked but only if the same generations. So 5800 was cross compatible with 6800 and 7000 with 8000 but there was a tiny difference in shape which meant you couldn't cross the two.

    Looking at pics of 9200 Vs 8100 looks a similar situation.

    But would I want to lay down the vast amount Shimano charge for a new outer ring to be the guinea pig? Not a chance. I would pick up one of the large amounts of 8100 chainsets listed on eBay second hand as everyone switches to shorter cranks. Will probably be the cheapest way to get the rings anyway - if you want to try to fit onto your DA cranks then please do and report back...

  • daniel_b
    daniel_b Posts: 12,135
    edited January 27

    .

    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • This is what I would do. Had a look on ebay earlier and there are 8100 chainrings in 50/34 in good condition knocking about for around £60.

  • skinnydog
    skinnydog Posts: 60

    Sorry for my lack of clarity, it was swapping out the chainrings from the spider. So removing the DA 52-36 chainrings and swapping with the Ultegra 50-34 chainrings.

  • super_davo
    super_davo Posts: 1,250

    And I'm saying probably cheaper to get a second hand complete crankset than the rings, which takes out any worry about compatibility. Once you've got you could swap the rings over to check if it does fit, and if you do... Please report back!

  • The chainrings are compatible but youre likly cheaper buying a whole new chainset as the big chainring in any size is hideously expensive

  • daniel_b
    daniel_b Posts: 12,135
    edited January 27

    £15 / £100 gamble likely (not) worth it?


    Reputable bike shop, if you call them they might even be able to tell you whether they will fit.


    EDIT: thought it was £15 the pair, but it's £15 for the 34, and £85 for the 50.


    I'm seeing complete 8100 cranksets out there for ~£110.


    Alternatively if you are prepared to drop to 105: https://www.bikeparts.co.uk/products/shimano-105-fc-rs520-double-12-speed-chainset-172-5-mm-50-34t-black

    I don't think I would on a DA bike though to be fair, I might be able to be persuaded if it was just for a couple of weeks a year.

    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • skinnydog
    skinnydog Posts: 60

    Thanks for all the replies gents. Appreciated. 👍

  • daniel_b
    daniel_b Posts: 12,135

    @skinnydog Please let us know what solution you end up with, and how you found it, both in terms of the change, and out on the mountains :-)

    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • skinnydog
    skinnydog Posts: 60

    Yeah, will do, although not going till July. ( I like to be organised well in advance 😁) Riding to ferry port at Rotterdam from Venice, via the Julian Alps in Slovenia and Austrian Alps, a 34 inner will just give another get out of jail card.

  • laurentian
    laurentian Posts: 2,609

    If it's just a temporary thing (and you're not too fussed about aesthetics) have you looked at a possible FSA solution?


    e.g.

    https://www.bikeparts.co.uk/products/fsa-omega-10-11x-172-5mm-34-50t?variant=44646710837405&gad_source=1&gclid=EAIaIQobChMIve_Uy5KYiwMVLJVQBh0UAi4fEAQYASABEgJdY_D_BwE

    Wilier Izoard XP
  • Misread your first post. Agree, if you can get a whole cheap crankset definitely better to do this.

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