Chainring. Swap

Discussion in 'Bicycle Mechanics and Repairs' started by Thomson, 15 Apr 2019.

  1. Thomson

    Thomson Well-Known Member

    Hi total bike noob here.

    Looking to buy a cannondale 2019 synapse Tiagra disc.
    Comes with a fsa megaexo bottom bracket and a fsa omega alloy 50.34 chainring. I would like to swap the chain ring for a Shimano Tiagra 4700 50.34 chainring. Just so it matches and keeps the group set the same.

    Would this be possible? If somebody could find out or help it would be very much appreciated as I havnt a clue.

    Many thanks.
  2. The mega Exo Bottom bracket spindle hole is 30mm, the hollowtech 2 spindle ( Tiagra ) is 24 mm. You’ll need reducer shims or a full bottom bracket adaptor.
  3. Smokin Joe

    Smokin Joe Legendary Member

    It would as RR says, but there would be absolutely no point to it. Even pro teams don't always stick to the groupset chainset.
    Cycleops likes this.
  4. Actually I think the mega exo is a 24mm spindle on this bike. I don’t know if the lengths of the mega exo and Shimano spindles are the same though.
  5. OP

    Thomson Well-Known Member

    Thanks for the replies. I know there’s probably no need to change it but I would just like it to match that’s all.

    Thanks both off you :-)
  6. Last edited: 15 Apr 2019
    Thomson likes this.
  7. OP

    Thomson Well-Known Member

    Thank you rr
  8. ianc6472

    ianc6472 Member

    I have a 68mm/122.5mm Bottom Bracket with 3 gears, I want to change to a single chain ring.

    My question is, as my BB is shot, do I need a smaller BB spindle size?
  9. Are you asking if the spindle length needs to be shorter?
  10. FWIW I used an FSA adapter to convert my BB30 Cannondale so I could use HTII, and it's never been an issue :okay:
    Racing roadkill likes this.
  11. ianc6472

    ianc6472 Member

    Yes do I need a shorter spindle?

    Logic tells me that I will need a shorter one! But I’m not sure that the new Chain ring would, should be in the same place as the smallest ring from the old 3 set?? That would also be logical wouldn’t it??? Or does it matter as the chain moves over 3 different positions anyway!

    It’s got me beat as the only way of knowing is to try all of them, or is there a logical method of working it out?
  12. A 117.5mm spindle would be ideal, but the one you have will still work, but the ring will be a bit further from the stays.
    ianc6472 likes this.
  13. ianc6472

    ianc6472 Member

    Thanks for the reply, my choice is 113mm, 118mm or get a new 122.5mm so middle of the road it will be then.... or maybe I will try my old shot 122.5mm first for size to see where I’m at, then go from there. Thanks again
  14. The 118mm will give you a better chain line.
  15. ianc6472

    ianc6472 Member

    I have an 8 speed on the back so I’m aiming for about middle of the set. Decided the plan is to measure it from the old BB, but I’m sure your right it will be 118mm
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