The problem is, that by buying stages you are only measuring power from one leg and then multiplying it by 2. In most cases this is neither accurate nor consistent.
Take me for example... I know from last season that my power balance is c. 50/50 at TT intensity. This would suggest that a stages power meter might be effective for me in those circumstances. However I also know that my power balance wavers from 50/50 under different circumstances and sometimes quite significantly.
Looking at my last few rides I see that my 2x20minute efforts today were 49.8/50.2 and 50/50 respectively, however my warmup was slightly left dominated (51.5/48.5) and my rest period was slightly right dominated (49.2/50.8). These aren't huge swings, and so maybe stages might produce similar data.
By contrast, my last club run was 120 moderately hilly km where I misjudged my recovery from a recent cold and spent the day dangling before being telling the group not to wait and limping home. Over the entire ride, my average balance was 52.9/47.1 however the final few kms where I was really struggling were out at 57/43! Just taking my left leg data and multiplying by 2 would have given all sorts of bizarre readings and would be completely useless!
The average power balance on the club run before that was 56.1/43.9, again with the greatest imbalance coming when I was severely fatigued.
Measuring L/R power balance seems to be pretty pointless from a performance perspective (there is no evidence that I know of that says the fastest riders are most perfectly balanced) but it is interesting data to see how power balance is both different for all different riders, but also how different it is in different circumstances (whether within ride variability or between ride variability).
If you know that your power balance is 50/50 then stages would probably provide pretty accurate data. Even if you know that you have a consistent imbalance across all conditions and circumstances then you could at least get consistent but inaccurate data. But if you are like me (or others that I've spoken to) then you are probably neither of those and in that case stages will be worse than useless.
Stages ≠ accuracy argument never wins. Thats how they've built their brand and have a world tour team sponsorship. They know that and the USP is 'minimal, cheap and light'.
The problem is, that by buying stages you are only measuring power from one leg and then multiplying it by 2. In most cases this is neither accurate nor consistent.
Take me for example... I know from last season that my power balance is c. 50/50 at TT intensity. This would suggest that a stages power meter might be effective for me in those circumstances. However I also know that my power balance wavers from 50/50 under different circumstances and sometimes quite significantly.
Looking at my last few rides I see that my 2x20minute efforts today were 49.8/50.2 and 50/50 respectively, however my warmup was slightly left dominated (51.5/48.5) and my rest period was slightly right dominated (49.2/50.8). These aren't huge swings, and so maybe stages might produce similar data.
By contrast, my last club run was 120 moderately hilly km where I misjudged my recovery from a recent cold and spent the day dangling before being telling the group not to wait and limping home. Over the entire ride, my average balance was 52.9/47.1 however the final few kms where I was really struggling were out at 57/43! Just taking my left leg data and multiplying by 2 would have given all sorts of bizarre readings and would be completely useless!
The average power balance on the club run before that was 56.1/43.9, again with the greatest imbalance coming when I was severely fatigued.
Measuring L/R power balance seems to be pretty pointless from a performance perspective (there is no evidence that I know of that says the fastest riders are most perfectly balanced) but it is interesting data to see how power balance is both different for all different riders, but also how different it is in different circumstances (whether within ride variability or between ride variability).
If you know that your power balance is 50/50 then stages would probably provide pretty accurate data. Even if you know that you have a consistent imbalance across all conditions and circumstances then you could at least get consistent but inaccurate data. But if you are like me (or others that I've spoken to) then you are probably neither of those and in that case stages will be worse than useless.