I run the Pioneer power meter, which is also on the crank arm for the non-drive side. I had to upgrade the rear brake to make it all clear. I have heard the same is necessary for Stages, not sure about 4iii.
For reference, I found a narrow TRP rear brake for under $100 that did the job, but the tri-rig is another option.
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TEAM F3 Undurance
For reference, I found a narrow TRP rear brake for under $100 that did the job, but the tri-rig is another option.
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TEAM F3 Undurance