After looking for some power meters, I decided to buy a pair of Garmin 3 for my road bike, but I have read about the problems in accuracy when using oval rings. In my case I have a Rotor QXL. Can someone please confirm that vector 3 works well, with no problems with this kind of rings? Or it drops wrong or inaccurate metrics with it? I'm interested in cycling dynamics, but I don't want to spend such amount of cash for a product that won't work as expected. Thanks.
Going by the ovality quoted on Rotor's website (16%) and assuming you arranged the oval rings to maximize the pedal speed at the top and bottom of the stroke (when torque is minimal) you could expect Vector to over-estimate your power by up to 2.56 percent. In reality, the error will likely be slightly less. The error factor will be fairly constant and you could likely substantially reduce that error simply by entering a slightly shorter crank length.
The torque and power calculations used by Vector 3 presume a constant pedal speed through the crank cycle. When this is not the case, the system will either under or over report power depending on how the crank ring is aligned with the pedal arms.
Going by the ovality quoted on Rotor's website (16%) and assuming you arranged the oval rings to maximize the pedal speed at the top and bottom of the stroke (when torque is minimal) you could expect Vector to over-estimate your power by up to 2.56 percent. In reality, the error will likely be slightly less. The error factor will be fairly constant and you could likely substantially reduce that error simply by entering a slightly shorter crank length.
The torque and power calculations used by Vector 3 presume a constant pedal speed through the crank cycle. When this is not the case, the system will either under or over report power depending on how the crank ring is aligned with the pedal arms.
OK, then I will expect a bit less accuracy with this rings, but seems nothing to worry about. How can I calculate the best setting for my crank length? I'm using a 175mm rotor 3d+. If I understand, seems that adjusting a bit less arm length will give me an average between the "fast" and "slow" ring side. Is there any table or formula for people using this kind of oval rings? Maybe will be a good idea because there are many people using rotor or similar oval rings. Thank you very much.
