I currently run Shimano 105/Ultegra/Dura-Ace (2X11) components on my road bike.

  • Chain Dura-Ace
  • Cassette & Crank 105
  • Derailleurs Ultegra

I am looking to replace my cranks when I wear out my next chain and want to experiment with different crank lengths (e.g 165, 170, 172.5, and inbetween etc.) without buying extra Shimano Cranks for $$$. I also want to make the jump up to 53/39 from 50/34 that is on there now.

I know Shimano does not make any adjustable length crank arms.

Do I have any off the shelf options to be able to use my other Shimano components and possibly use a 3rd party crank to get adjustable cranks without spending tons more than what I would on a Shimano Crank set?


---- Update

I'll probably go about trying to see if I can rent or try out a crank arm for a bit to ensure the fit is good and then buy the full ultegra crankset. Just as a bit of a follow up does anyone know if you can buy the right side crank arm on for an ultegra crank set new as I see the left side sold separately, but not the right?


  • 1
    Aren't you confusing crank length and chain-ring sizes? On any of the newer 110mm BCD Shimano cranks you can swap 53/39, 52/36 or 50/34 rings or even 46/36 cyclo-cross rings.
    – Carel
    Commented Dec 25, 2020 at 16:32
  • @ Carel, I modified the wording a bit. I am wondering about crank arm length. I do know on the Shimano cranks the rings are changeable/replaceable. I also was planning if I stayed with Shimano to just go with Ultegra cranks vs. just buying 105 chain rings just as a personal pref. However, ideally I could find something that let me use normal Shimano components chain ring back and gave me some options to try different crank lengths. Thanks Commented Dec 25, 2020 at 16:38
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    SRM Origin Carbon allows to switch between 170, 172.5 and 175 lengths, has 24mm spindle and accepts Shimano chainrings, but doesn't fit your cost requirements. Commented Dec 25, 2020 at 18:17
  • @Klaster_1 True, but it would get the OP a power meter. If we’re going with that sort of thing, then I’ll throw out Powercranks. This is not worthy of an answer, but they were a bit of a thing in the mid 2000s Among the tri crowd. The arms operate independently, so you are basically doing one leg drills the whole ride. There is a very lengthy adaptation process, and honestly I was not sold on the benefits (but I was rehabbing from a unilateral injury, and they helped with that). Some models have adjustable length.
    – Weiwen Ng
    Commented Dec 25, 2020 at 18:57
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    @TudeProductions : The R7000 aren't that expensive ~120-130€/$ when compared to DA probably less if you manage to obtain them without the rings through a friendly LBS or even on loan from a cycle mechanic.
    – Carel
    Commented Dec 25, 2020 at 20:06

1 Answer 1


There are sizing cranks that are primarily used by fitters. They're expensive and heavy and usually intended for a fit machine more than going on an existing bike. Ones I'm familiar with are square taper so getting them on to modern bikes would involve jumping through some hoops, but there may be a 24mm one out there.

Trying all the lengths in a short amount of time and with minimal contrivance would be a good thing to find a fitter's help with. Crank length and saddle fore-aft are numbers that play off each other, so you want to get your fore-aft dialed at the same time if you can.

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    I Googled real quick, and there are at least two parties that offer to rent you a sizing crank. But both are square taper. They are Zinn Cycles and High Sierra Cycles, link for the latter hscycle.com/adjustable-crankset
    – Weiwen Ng
    Commented Dec 25, 2020 at 18:02
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    Renting those sizing cranks would be a less absurd option than the SRM or the Powercranks that were ‘suggested’ in comments on the original question.
    – Weiwen Ng
    Commented Dec 25, 2020 at 19:02
  • @WeiwenNg - That link is very helpful and is what I figured had to exist in some form to help practically determine what crank length feels the best. Commented Dec 25, 2020 at 22:32

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