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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 articleSet Crank Arm Length for Power Meter Pedals

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, PowerTap P2, Garmin Vector 3 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!

Favero Assioma

Image of Favero Assioma DUO Power Meter Pedals

Garmin Vector 3

Garmin Vector 3 Power Meter Pedal

PowerTap P2

PowerTap P2 Pedals

SRM LOOK EXAKT

SRM LOOK EXAKT Power Meter Pedals
Josh Matthew

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10 Comments

  1. Avatar
    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
      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. Avatar
        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
        Sorin

        1. Power Meter City
          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. Avatar
          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.

          Benjamin.

          1. Power Meter City
            Power Meter City

            Absolutely. The Assioma app works perfectly as well!

  2. Avatar
    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
      Power Meter City

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

  3. Avatar
    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
      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!

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