HawkeyeCubs34

Does anyone have any experience using the P1S powertap pedals? They are power tap's new and more affordable power pedals, but single sided. If not, any opinions on single sided power meters?

Seattle Forrest

Your L/R balance probably isn't exactly a 50/50 split. And it probably changes as you ride.

Whether that makes sense or not depends on how important the money and data quality are to you. Power meters used to cost a lot more than they do now, and a lot of cyclists would tell you it used to make sense to consider a single-sided PM but no longer does. Of course, it's your money so it's your call.

Garmin's Vector pedals used to cost $1,700 and the left-only version was $800. Now, REI sells the dual-sided pedals for $1,000 and occasionally they go on sale for 20 % off.

Between all the PMs on the market, you can measure your (complete) power output for less money than P1s costs.

noglider 

If my legs are significantly differently powered, I want to know, but I suspect I would know without a power meter in each pedal. I suspect a one-sided meter is close enough for me. For whatever it's worth, I don't race.

Seattle Forrest

@noglider

I didn't know before I got a power meter that I'm left leg dominant. It's around 55/45 L/R, it happens on every bike I get on, but doesn't happen when I run. A left-only power meter would double the error.

noglider 

Interesting. What are the negative implications of uneven power?

SpeshulEd 

I have the P1 pedals (dual sided). They're great, would highly recommend them, especially if you have multiple bikes. DC Rainmaker went nuts for them, which is what lead me to them.

My legs are slightly different, and with the two pedals you can measure torque and pedal efficiency for each side, not sure if that's possible with the single sided unit. Still, if you don't care that it's slightly off, I can definitely see an advantage in saving a few hundred dollars.

Seattle Forrest

I dunno. To be honest I don't know if anyone does.

Some fit problems will cause a power imbalance. They'll also probably cause pain when you ride long enough. Fix the problem and both symptoms will go away. (Think of a saddle pointed the wrong way or tilted, like if one rail is bent.)

But some (most?) people just put our more power one leg for whatever reason. Maybe they favor one leg and it's slightly stronger than the other.

Anyway, you could put a lot of time and effort into correcting an imbalance, or, if it feels natural and isn't causing any problems for you, you can live with it and train to get stronger as a whole.

But if you're going to invest in a power meter, especially a single-leg one, it's good to be aware that some or many people don't put out even power through both legs. Now a P1s is cheaper than a P1 so maybe it's worth it to you. But on the other hand, if you don't need a pedal-based meter, there are even cheaper options that measure all the power you put out.

Here's a PowerTap hub with DT Swiss 240 internals for $300. It's just the hub so not the full cost of using it. You can get a used PT wheel in that ballpark. Power2max has a crank for $630.

noglider 

I paid attention on my ride this morning. Most of my riding miles are commuting. My route is about 27 miles round trip, which I do about two days a week. If I'm not fooling myself, I think there is a possibility I work harder with my left leg.

I'm not likely to buy any power meter, at least not soon. I am interested in building and maintaining strength, but I'm not eager to spend that kind of money. I track my distances and speeds with ridewithgps.

HawkeyeCubs34

Thank you all for your feedback. Power Tap stated that they will be coming out with a right side upgrade pedal some time in 2017. The idea seems to create a power meter for those who have a budget, but leaving the option open to have a dual sided power meter down the road.
If it's off by 10 watts for being single sided, then it's still better than not having a PM IMO if you can't quite fork over the cost of a dual sided PM. I would get the chain ring PM but it's not compatible with my bike and crankset.

SpeshulEd 

As long as you don't need/want both sides and don't mind a bit of inaccuracy when compared to other meters, you'll be fine. For the most part, the one-sided number will always be consistent with you. You'll learn your ftp and zones. If you move to dual-sided or a different power meter, your numbers might be off slightly, but they're easy enough to update.

gsa103

For the most part none. Team Sky ran single-sided Stages for a while, didn't seem to hurt them. I'm guessing the also cross-calibrated with double-sided or hub mounted meters prior to races.

There have been several studies that looked at the implications of asymmetric delivery, and basically revealed nothing. If I recall one study looked at efforts to balance power resulted in a power drop, since the stronger leg output was reduced.

For most riding, your power split is relatively constant (other than sprinting/standing vs sitting). One person might be 45/55 another might be 55/45, so they could read vastly different for the same total power. The split will basically be the same on a day-day basis, so if your power meter reads 300W, it'll also read 300W tomorrow for the same effort. This is why Team Sky could use it for training/racing.

As a training/racing tool, single-sided seems to be fine. The main downside is that double-sided meters are getting pretty cheap, so the cost savings isn't huge. When Stages first came out, it was half the cost of crank based meters, so it was significantly cheaper than a double-sided meter (PowerTap was cheaper, but required custom wheels). Now the savings is frequently only ~$200 compared with $600-$800 when Stages appeared.