Well the good news is…you have a lot of options. I guess this is also the bad news as it can make deciding more difficult! 🙂 Ok, here goes:
Left Crank Arm Power Meter
4iiii and Stages Cycling both make crank arm power meters for Shimano R8000.
You swap out your current left crank arm for the new power-equipped one and you are good to go.
Please note, whenever you are installing a left side power meter crank arm, you need to confirm you have 10mm of clearance between the left crank arm and the chainstay in order for the sensor to clear. Please see the image below.
Pros: Affordable, easy to install, don’t have to change crankset
Cons: Measures left leg power only
Crankset Power Meter (Spider Based)
This is a new crankset (power meter spider, crank arms and spindle), excluding chainrings. power2max makes wonderful power meters. They measure both left and right leg power, are reasonably priced and are as good as it gets in terms of reliability. If you select the 24MM spindle option, it will fit your current bottom bracket exactly like your Shimano crankset (no need to change bottom brackets). In addition, if you select the Shimano 4-Bolt spider, you can even use your Shimano R8000 rings on it.
This too is a new crankset (power meter spider, crank arms and spindle) and can be purchased with or without chainrings. The INspider measures both left and right leg power, comes in a variety of crank arm lengths and can be set up in a 1X or 2X chainring configuration. This power meter can also be purchased with a 24MM spindle so it will fit your current bottom bracket without any changes. You can use your current Shimano chainrings on it or buy new ROTOR rings.
Pros: Moderately priced, VERY reliable, measures both legs
Cons: Have to change your crankset
Crankset Power Meter (Crank Arm Based)
In addition to making left side crank arms for Shimano, 4iiii and Stages also make complete dual-sided R8000 cranksets. With these power meters, you get a new Shimano crankset with a power sensor attached to the inside of the left and right crank arm. Therefore, they are able to measure power from both legs as well as tell you how much power each leg is producing individually.
Please note, as with the left side power meters above, you need to confirm you have 10mm of clearance between the left crank arm and the chainstay in order for the sensor to clear.
Pros: Measures both legs, provides independent left/right power
Cons: More expensive
Power Meter Pedals
Power meter pedals can be installed on any crankset. We have several models to choose from.
Pros: Easy to install, works on any bike, can move from bike to bike, don’t have to change crankset