Advice on Power Meter
 

Good Morning All,

I am looking for my first power meter, looking for the most affordable options as I am on a budget. Currently using Shimano 105 R7000 groupset.172.5mm length crank set. Thoughts?

Used.

What modes specifically?

I'm glad I got a dual-sided power meter (Stages LR), because if I had gotten left-side only (and then it just doubles it) my power measurements would have been too high. Apparently I favor my left side by 3-10% depending on the difficulty of the effort.

How much are you willing to spend? The Stages LR is currently a bit over $700. A used single-sided power meter could probably be had for just a couple hundred.

Note that a lot of power meters are out of stock right now, likely COVID related issues with inventory.

While I'd like to think used is the way to go, what I've been seeing is that people are paying nearly new prices on eBay for used power meters which makes no sense to me. I personally would rather pay an extra $50 for a new, warranted power meter than a used one that may or may not work.

Competitive Cyclist has a one-sided Stages 105 for $300. I have a Pioneer Ultegra that I've been very happy with but I don't think the colors will match...

Used SRMs are a great option.

Stages for $300 seems like a good deal too.

I hear good things about Asioma.

https://store.stagescycling.com/closeout-cosmetic-blems
As far as I know shimano hasn't changed their spline interface so it doesn't have to be a r7000 and match. Just has to be the same length.

Depends on how budget-constrained you are -- wired SRMs and PT hubs are out of fashion but rock solid. Everyone seems to want pedal or crank arm PMs so used hub and crank spider PMs are cheap. I know a guy who got a PT G3 hub in January in a wheel with a still usable tire for $225; the former owner bought a pedal PM. We checked it out and it reads accurately, and the wheel was true. If he ever wants a pedal or crank arm PM, he can keep this as a backup, or as a control, or to do aero testing.

Used SRMs are a good option. Even wireless ones can be found on the cheap.
One downside with SRM, except Origin, is that battery is not replaceable or rechargeable. So you have to send it in every couple years or so. Which is 2-3 weeks without a power meter.

I got a 5800 4iiii left arm power meter for a pretty good price. I’d say 4iiii is a good bet (I have the coin cell one). Stages also recently reduced their prices significantly.

I’d like to warn against left only power meters though. I can’t actually confirm if this is true, but at lower power levels (under threshold), my left leg “drags” a bit. But my left leg kicks in hard at or above threshold. So if I’m trying to do a certain amount of power just under threshold, or if I’m spinning kind of fast, the PM will read low. I’ll make a slight increase in effort, and my left leg will kick in, and the power reading will jump.

So if you want a PM for pacing reasons, or to do longer intervals under threshold, I would recommend something that reads overall power.

Anyone know anything about iQsquare?

I bought a pedal based PM because I wanted the portability that comes with that - no issues of brake type or different BB standards, plus I can bring just the pedals and go rent a road bike in Utah vs bringing my own. I bought a dual sided because I felt like single sided was too much $$ to spend to still not know what I'm putting out.

Then I injured my feet and ankles, badly, one side worse than the other. Now that I'm mostly recovered, the L/R data is valuable to me.

The damned thing is, you don't know if you need two sided until you've got it, and then you find that you do or don't. I was convinced that I had more power in my right leg then left, so I bought the 2 sided Favero Assioma pedals (great power meters, btw). With those, I've NEVER seen a ride where the imbalance was greater than 52/48, and there are times that each leg has provided greater power over the course of the ride. So I didn't need 2-sided, except to learn that I don't have an imbalance.

I like these, I will probably give them a shot.

I learned rather quickly that dual-sided means next to nothing to me. If I'm over 70% intensity, it's 50/50. If I'm under 70%, it's 51/49.

This is true, but the batteries last about 5 years of regular use, so it's not a frequent requirement. Also, when they replace the batteries, they check the system and calibrate it, so you know your PM is still accurate and working well.

I have the same thing except opposite legs. The difference in power output is greater the further below threshold I'm at. At a threshold pace it's usually just 2-3% different between my legs, but I've seen as high as a 60/40 L/R split on efforts well below threshold. Since those efforts aren't meant to be high power I'm not sure if this is a problem I need to work on or not, and I had no idea I rode that way until I got the PM. I totally agree on the left-side-only option being insufficient, though, and as Seattle Forest said, if you really want to know what you're doing then it's dual-sided all the way.

I just got a Stages and it's great. They work with any hollowtech II crankset, all the way back to DA 7800, which is what I happen to have on my TT bike. It was an inexpensive and easy way to get power, especially since it does both BT and Ant.

There are lots of things you can do with a power meter and some require more accuracy, while others require less. Most (?) riders just use a PM for training FTP, and training FTP is one of the least demanding things you can do with power data, so most riders can get by without needing much accuracy. Unfortunately, if you're new to using a power meter, you rarely know what you're going to do with it a year or two down the line. This is partly why I think getting an inexpensive used power meter that's rock solid and gives good quality data is almost always a good idea as a first PM. You'll learn what to do, you'll see whether you have some oddity in your pedaling that would have screwed up your data, and you'll figure out whether you want to do more than just training your FTP.

Hopefully not throwing this post onto a total rabbit trail... What do you do if your right and left power measurements are off? Single leg drills? I think most of us are asymmetric as far as our muscles are concerned (i.e., I'm right handed so I favor my ride side which is noticeably stronger.) Unless I plan on somehow correcting the asymmetry, I'm not sure it matters if I know it's there(?)

It depends on why there's an asymmetry, how big it is, and what you need the data for. I do some things with a power meter that require accuracy across the entire range of power from low up to high, so even if I weren't going to try to "train" it away, variable asymmetry would screw up my calculations if I just assumed the asymmetry were static. That said, what I do isn't terribly common, so I try not to fool myself into thinking that everyone has the same needs as I do. This is just an example that it depends on what you're trying to do.

The reason it matters is because the asymmetry can change depending on output. So if you’re on rolling terrain, you might see your power output jump on steeper sections because you crossed threshold torque. Instinctively, you’ll shift down, but then your power reading will drop like crazy and you’ll find yourself doing 400W when the target was 180. Ask me how I know.

There’s not much evidence that I know of to suggest that you should try to correct it, especially if the asymmetry goes away at higher efforts. If you’re well below threshold, your body doesn’t really fatigue any quicker using one leg way more than the other - you’re just burning fat. In fact it’s probably more efficient (because otherwise you wouldn’t be doing it).

I used to worry about L/R imbalance, but now choose to ignore it. Why? Two of my four power meters provide L/R imbalance; one consistently says my left side is stronger (53/47) while the other says my right side is stronger (46/54). (The overall power for all four meters is within 1-2%.)

I’m using the PowerPod V3 Lite and it works fine for my purposes. It was $199 and with a software upgrade (for a cost) it offers way more capability than I need. I am using it to see improvement in power output so as long as it is consistent I’ll be happy.

That's kind of disturbing.