I have the opportunity to spend a few pennies on something for the bike and I was wondering about buying a left crank only power meter. I have the power meter in my Elite Direto but frankly as the sun starts shining training indoors is depressing. Is it worth it or should I just wait and save for the considerably more expensive dual sided (not likely this year)?
1 Like
I’m very happy with my Stages left-only power meter but I also got a great deal on it compared to any full-power solutions.
8 Likes
I would not hesitate going left only depending on what your needs are. I purchased a left only 4iiii Precision and it has been great getting TSS and power numbers for all rides both inside and out. I am a bit of a data nerd. I tested it against the Neo when I first purchased and average/normalised power over an hour ride was very close. I do not race so super accurate/left right balance etc would be interesting but not needed.
6 Likes
Love my 4iiii. Been superb for me
6 Likes
Velonews tech mod episode 12…all about power meters…listen and you will see left only is the best deal for the money…btw 4iii left only here…
7 Likes
I’ve got a couple of Stages on my mountain bikes and they have worked well. Mountain biking you can get some power spikes if you are left leg forward on descents, but I would think that would be less of an issue on a road bike.
The main thing you lose with a left side only is the ability to assess power difference between legs. For most riders probably not such a big deal, but if rehabilitating an injury it might be.
3 Likes
I have a Stages meter on my road bike and ancient Elsa R with only Ant+ on my CX bike which was too cheap to pass up. If I didn’t have a smart trainer I would realize more value in the Elsa R which measures left and right. However, I’m more irritated that it doesn’t use Blueteeth so I’d love to sell or trade it for a single side meter. If you are looking for a Stages I recommend only gen-3 for it’s better connectivity through both Ant+ and BT. I should note that Stages replaced my gen-2 meter with battery life problems for free, outside of warranty.
2 Likes
Left only is perfectly fine.
I was listening to some of the older Ask A Cycling Coach podcasts on auto play, so can’t say which episode it was, but Chad was basically saying, even if you have an imbalance, which 99.99% of people would have, because, hey, we’re human and not perfect, that it’s near on impossible to train to remove the imbalance. So all that dual is really going to tell you is what power what leg is putting out.
The most important thing is consistency - FTP numbers only relate to you. Power output only relates to you. If you use the same tool, and using that tool, over time, enables you to increase your power, your FTP, 10%, then it’s 10%, irrespective of the power meter measuring one leg or two, or measuring 10% lower than another brand. Your other leg isn’t getting left behind in the development stakes, else you’ll find you will only fit in one leg of your jeans… 
Power output numbers from the sensors only really matters if you’re mixing brands and types of power meter (like DC Rainmaker, or GPLama).
Go for single sided, and you’ll be more than happy. 
11 Likes
4iii, Powertap P1s, Assioma Uno
Unless you are pro who really, really, really needs to know left-right balance single-sided will be fine.
Knowing L/R balance is only useful to me as a strange edge case. I have Powertap P1s on my TT and a Stages on my road bike (I have a special snowflake reason for this which I won’t bore you with), so I know my balance is left heavy and that it gets worse as I get fatigued and/or at higher watts. When I get home from a road ride and see a scary NP/TSS from the single sided meter, I know I can discount it a bit and not worry so much about having blown my TSS for the week.
Like I said, strange edge case there. Single sided is a great investment and I think double sided is a marginal (but cool and fun!) gain given the cost. I’d jump on single sided if I were you to make the most of your riding year. Make sure you use powermatch indoors though to make the indoor and outdoor rides more comparable in the context of training even if your trainer is more ‘accurate’ in balance terms.
Single sided is fine. The only thing you’ll get with double sided is more numbers to over-think. (TFIC)
3 Likes
Hi BaronGreenBack,
(Full disclosure, I work for Avio, we make PowerSense left crank power meter)
Left crank only power meters are certainly the most affordable way to get power data and the power data you get is excellent and will give you all the same numbers as SRM, Powertap, Vectors etc.
As you know from using your Direto, power is by far the most reliable data to get you stronger on the bike and there’s no alternative to being outside!!
Didn’t Chriss Froome won TdF using leff only stages power meter… ?
2 Likes
Thanks for all the info. I have the sensor with the Direto so I can work out if I have any imbalance before I set up the power meter. Only issue now is crank clearance. It’s showing as just a little too tight close to the bottom bracket.
No. They were on LR for a long while before they hit the market.
2 Likes
*May give you the same numbers. There’s some shitshow power meters out there that I wouldn’t mention in the same sentence as others.
1 Like
He won his first two Tours on left only. First testing of the dual sided Stages was in 2016 but Froome didn’t use it that year.
Mike
1 Like
Dang. Let’s hope Froomedog is 50/50 on the pedals or the data is junk 
They’re on Shimano power meters now.
Interestingly the article I linked suggests that Sky requested dual sided because they thought they might be missing out. Turns out it didn’t made any difference to what they were doing.
Mike