I recently purchased a LR power meter–I've had a left only on 3 of my bikes before this, and they've given consistent ratings. My first ride on the new one produced much lower power ratings. There seemed to be something wrong, and they sent me a new one. Same things' happening. In both cases, the meter is reading about 65-35 for balance. (65 left, 35 right) I have never had an accident or noticed my legs being much different in strength. I know that SOME imbalance is very common, but 65/35 seems extreme. What I'd like to know is how likely it is that this is my true balance versus the power meter (which is a new product; won't name companies).

If I'm truly that lopsided, is there anything I can/should do?

Also if anyone has suggestions about how to resolve this question, I'd appreciate the advice.

1. Can you do a static torque check?

2. If not, you'll have to do a dynamic check. That's a bit more of a PITA.

I don’t know how to do either. Do they require fancy equipment?

Find a buddy with a powertap wheel and an extra head unit and compare the output (won't explicitly address the balance question but will help you determine whether the right leg is underreporting... might be easier than any technical procedure). I'd say that's an extreme difference

A static torque check usually requires some weights of known mass -- like barbell plates. However, in your case, since the discrepancy is so large, you might not need laboratory accuracy; you could probably just use your body weight. Balance first on the left pedal and then on the right, and check the torque reading to see if they're close. [Edited to add:] Since the discrepancy is so large, just put your bike parallel to a wall with the front wheel wedged into a corner with cranks horizontal. Then put your head unit in torque mode and stand on the left pedal, with maybe the backs of your fingernails of your left hand against the wall to support you. You don't want the weight to be supported by your hands, which is why you're using the backs of your fingernails on the wall; they're just for balance. Then do the same thing for the right pedal. The whole thing should take about 2 minutes.

If you can't do that, then you have to do a dynamic test. Ride up a steep hill first at slow slow speed; then at fast speed. Then go to one of the online power websites, like analyticcycling.com, and see whether the power for your speeds is about right. If the hill is steep enough, you don't have to worry about aerodynamic drag.

Simplest would be to have a friend ride your bike. If they get similar imbalance numbers to you it is probably the meter.

Beat me to it. I would try this too. Also I would try to ride another friends bike with a pm to check there if you could.

65/35 is extreme. Get a buddy to test also, but I'd wager quite a bit that something is messed up. I broke my femur & those numbers represent my initial imbalance on the first rides after the break.

What'd you find?

As for your first question, the answer depends on whether you're achieving your cycling goals. If so, no, there isn't much you should do -- if you weren't previously aware of such an asymmetry (and you've verified it), it wasn't affecting your cycling goals.

The noted cycling coach Alex Simmons has been using a power meter for years, and competed at a very high level both in road and track racing. Then, several years ago, he had an unfortunate accident that eventuated the amputation of his left leg above his knee. He has a pretty severe bilateral asymmetry, and also power data from both before and after the incident. There isn't much he can do about his asymmetry so he just focused on training his total power. It took him couple of years of serious rehab but ultimately he was able to surpass his pre-incident FTP.