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Banner image for our Set Crank Arm Length for Power Meter Pedals article

Set Crank Arm Length for Power Meter Pedals

Banner image for our Set Crank Arm Length for Power Meter Pedals articlePower Meter Pedals Crank Arm Length

When using meter pedals, your bicycle computer or head unit needs to know how long your crank arm is in order for it to properly convert the force you are generating into watts. The default setting on power meter pedals such as the Favero Assioma, Garmin Rally, or SRM LOOK EXAKT is 172.5 mm. If this is the length of your crank arm, you’re in luck. There’s nothing for you to do here. If your crank length is not 172.5 mm however, your power will be off. You could expect a power difference of about 1% based on the difference in crank length. So if your crank arms are not 172.5 mm, you will want to set the correct crank arm length.

Setting your crank arm length is easy to do. It just requires that, once your power meter is paired with your head unit, you select the appropriate crank arm length on your head unit. So don’t forget to set your crank length when installing a set of power meter pedals. It’s a quick and simple way to ensure your new pedals give you accurate power data!

Josh Matthew

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  1. Rodgcil

    Hi there. I have the assioma duo which I installed to my spin bike.
    The crank length in my assioma app was set to 150 mm. i tried to change to 175 mm (using the assioma app) but every time I do it, it takes forever to change the setting. The next time i check it, it is still at 150 mm. What can I do?

    1. Power Meter City

      Hi there. If you are using a bike computer, you can try changing it there. I’m not sure why your app keeps reverting back to 150. A bit of a strange problem and I would send Favero a quick note so they can look into that for you.

  2. Ivan Murdock

    I have a SRM PC8 – it will let me set it to 170 – says success but if I go back in it defaults back to 172.5 – Not sure why

    1. Power Meter City

      Hi Ivan. Thanks for the message. Yea, that’s a glitch in the PC8, it shouldn’t be doing that. You can try to do a hard reset by pressing and holding the PRO, MODE and SET keys simultaneously for three seconds. If that doesn’t fix the issue, I’d recommend reaching out to SRM for further guidance. Thanks!

  3. Michael Tate

    I do want to note that there are some head unit manufacturers (Wahoo in the case I’m aware of) that only allow you to set your crank length between 165mm and 180mm. So if you have short cranks, you’re SOL.

    1. Power Meter City

      Hi Michael. Yes, you are correct – thanks for the note!

  4. David B

    Does the power meter pedal receive the crank length setting each and every time it pairs with a head unit? I’ve got Assioma Duo and Garmin Vector 2 pedals on different bikes, so different bike profiles on my Edge 510, one with 172.5 and other 175. I guess the safe thing to do if I realize I paired the pedals with the wrong bike profile on the Edge 510, is select the correct bike profile, then unpair and re-pair the pedals again? Really love the Assioma pedals I purchased from Power Meter City!

    1. Power Meter City

      Hi David. Yes, you only need to set the crank length in the computer one time for each pedal and it will save the setting. We’re glad to hear you are enjoying your Assoimas!

      1. Sorin

        I have the same problem:
        – I have Assiamo Duo with default length for crank 172.5, while I have 170 on the bike. And with Garmin 520 Plus I have no option to set the crank length.
        I just can calibrate – pedals on vertical positions.. but I am not supposed to do that every time and not sure either if the crank length is detected automatically
        Please advise
        Thank you

        1. Power Meter City

          Hi Sorin. The Garmin 520 does indeed allow you to set the crank length. Specifically, you navigate to the sensors menu, select your pedals and then go to Sensor Details > Crank Length. Once you do this, it will be stored and saved in the 520.

        2. BATICLE

          Or you can just use the Assioma app on Android or iPhone to set the correct crankset lenght, it works the same than if you were using your head unit.


          1. Power Meter City

            Absolutely. The Assioma app works perfectly as well!

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