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SRAM Rival AXS Power Meter: Hands-on and First Rides

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In the world of cycling drivetrain gear, both SRAM and Shimano have three core pricing tiers for their wares. In Shimano’s case that’s Dura-Ace, Ultegra, and 105. While in SRAM’s case it’s RED, Force, and Rival. These companies release their best and fanciest stuff at the top end, and then roughly every 1-2 years it trickles down to the next level, and so on. Rinse and repeat for decades.

Today, SRAM trickled down the eTAP AXS to their ‘budget’ range – Rival. This marks the first time that SRAM Rival has seen wireless shifting, but also the final layer of that three-layer chip dip to become fully wireless. It also marks the end of mechanical shifting for Rival, as well as marking the beginning of disc-brake only offerings, as Rival won’t come in a rim-brake version.

But perhaps more interestingly for some readers here, it introduces an entirely new type of power meter for Quarq, SRAM’s power meter brand: The Rival AXS power meter. Unlike past Quarq spider-based systems, this spindle-based system is more akin in functionality to a left-only single-sided power meter. Essentially, you swap out your left crank arm plus the spindle, which includes the power meter inside of it.

Now I’ll circle back with a full review of the SRAM Rival eTAP AXS gear after a bit more riding, but I figured I’d explain the power meter for now.

Rival AXS Power Meter:

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To begin, let’s look at some quick specs, and then we’ll take a closer inspection of the unit:

Claimed Accuracy: +/- 3% (but it’s actually +/- 1.5% doubled)
Measurement point: Spindle
Dual-sided: No, left-leg power only
Added weight: ~40g
Protocols: ANT+ & Bluetooth Smart
Zero offset supported: Yes
Battery type: AAA Lithium
Battery Duration: 400 hours
Waterproofing: IPX7 (thus 30-minutes at 1-meter deep)
Pricing: $249 for upgrade kit, or $349 for complete crankset including chainrings

Now the key thing there is that it’s a left-only power meter – all spindle-based power meters are, like the ROTOR inPower, because they’re effectively only measuring the torque from the left on the non-drive side. That below with the hole, is the spindle, that piece that connects your two crank arms together:

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This is different than the rest of Quarq’s power meters, which are spider-based and measure total power (but can vaguely estimate left/right balance). Then of course there’s dual-sided power meters, like the PowerTap power meter pedals that Quarq acquired, and recently discontinued.

Ultimately, the Rival AXS power meter from a power composition standpoint is similar to a left-only Stages or 4iiii unit (or any other single-sided company). They take that power and simply double it. So, if your power balance is roughly equal, it’ll roughly work out. Whereas if it’s skewed lower or higher, that skew would be exaggerated when doubled. But more on that later.

The entire point of the Rival AXS power meter is that it can be installed on any Rival AXS equipped bike, theoretically easily. From a bike shop standpoint, that’s certainly true. Though, from an end-consumer standpoint, swapping out a spindle and a crank arm (and first detaching the drive-side crankset) is hardly 1-minute type work. Here’s what the upgrade kit looks like (sorry, I haven’t disassembled the test bike yet, for reasons that’ll become obvious in the next section):

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The left-arm (non-drive side) has a small battery compartment in it, which holds the AAA battery. You can untwist the cap to access it. That battery pod then plugs in to the far side (drive-side) of the spindle internally. If I shine a flashlight down there I can see the connector.

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At that point you can pair it up to any head unit that supports power meters, from Garmin/Wahoo/Hammerhead/Stages/etc… and use either ANT+ or Bluetooth Smart. For ANT+ it supports unlimited connections, and for Bluetooth Smart it supports a single concurrent connection.

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You can also use it with apps like Zwift, TrainerRoad, Rouvy, The Sufferfest, and more. As long as they support ANT+ or Bluetooth Smart power meters, you’re good to go. And of course they do – they all do.

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In addition, the Rival AXS power meter can be paired up to the SRAM AXS app, where you can check settings and save it to your virtual bike.

At this point, it was time to get out on the road and testing. From a basic usability standpoint, it’s no different than any other power meter. It’ll transmit total power (wattage) and cadence (RPM). It won’t transmit power balance, since it can’t measure that.

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And here’s a quick look at the type of information you’ll see afterwards from your bike computer:

With that, let’s dive into the data itself.

First Rides Data:

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So I’ve got a few rides on this, and it’s been a mixed bag. On my first ride, I threw on a pair of Rally RS200’s. I did some settling, a boatload of zero offsets of all the units, set the install angles for Rally, went outside, waited for temps to settle, etc… And then I rode.

And then the data wasn’t good. The Quarq Rival was some 40-50w lower than the Garmin Rally pedals. Now, if I know anything about power meters, it’s that first rides after installs can be iffy while things settle. But never this iffy. If I know more about power meters I know that in general, more things can go wrong with pedal-based power meters than other places. Thus, my initial assumption was to assume that Garmin Rally was acting up. But I’ve moved these pedals around A LOT over the last few months, all without issue. So over the course of 30 minutes, while riding, I did a slew of troubleshooting steps on both units to try and get them to agree. Nearly 2 hours later, I couldn’t. They just had to agree to disagree.

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And of course, that’s the problem with only two power meters – you never know who exactly is right. Of course, with a 50w split, one could probably do a Virtual Elevation pass on this and get a good ballpark estimate which one is right. Instead, I just sent off all the data to Quarq and said: You sort this out.

They sent me back a small set of data points to try, and the next day I went back inside and got it all set up on a KICKR and did some additional zero offsets of all the units, including a suite of zero offsets on the Quarq at four positions. After all that was done, I started pedaling. And all three units (now including the KICKRV5) agreed mostly happily.

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There was a second or so lag on the Quarq Rival, but nothing I was worried about at the moment.

So then, without stopping the bike computers, I took the bike off the trainer and went straight outside for a short test loop of a few minutes. Sure, temp comp might not be perfect, but frankly it’d be quick enough that neither unit’s materials would shift that fast anyway. As you can see, the data here looks pretty good too. Same slight lag on Quarq, but nothing to focus on at the moment:

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Ok then…fixed, I guess?

I got on a conference call with SRAM/Quarq to discuss, and ultimately none of us can know which unit was incorrect on the first ride. However, they did look at the numbers I gave them from the zero offsets, and there does sound like there’s a bit of concern there – specifically on alignment between the four position offset numbers.

Thus, out I went again an hour ago for another loop – this one about 40 minutes, inclusive of some gravel terrain as well. And at first, things weren’t ideal (an 18w difference on ~200w, with Quarq reading lower). However, at about the 26ish minute marker I woke up and realized I was in the small-ring up front, and shifted to the big ring. At that point, the difference shifted to 30-40w offset.

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That’s weird.

So, switching over to a PowerTap P2 pedals and back out for another loop. Equally far off 40-50w total power.

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But then one of the SRAM engineers brought up an interesting point, looking at the previous data set with Rally – the left-side of that set actually matched the left side of the Quarq/SRAM Rival. And since left is doubled, in theory those matched (this set is against the Garmin Rally pedal set):

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That’s both good and bad for Rival. It’s good in that from a technical standpoint, their left side matched Garmin’s left side. It’s bad in that for some absolutely bizarre reason, my left leg balance has gone to crazy town on this bike. My normal balance floats at 50/50 for most rides, +/- 2% either direction. Yet, for all but the trainer ride (which, isn’t explainable), my leg balance on this bike is way askew.

My best guess here is that this bike is too small for me (it is, considerably), and thus, my pedal stroke is substantially different. If I look at my regular bike data from earlier this week, I’m just fine balanced at 50/50 for the ride.

So then, what about that PowerTap P2 pedal ride test and the balance there? Well, it decided to split the difference. Yes, my left/right leg balance is definitely offset according to the P2 pedals. But then the SRAM Rival power meter went even further than that. Doubled-up, I hit at almost 60w off.

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At this point, I’ve tossed the data back to Quarq to let them sort through and think about. I agree with them that there’s definitely some odd me-specific balance thing occurring here, but I’m also seeing in the P2 dataset it being more off than can be accounted for. More testing is needed, though, I suppose it does highlight the rare scenario where even if the accuracy is perfect, that a left-only power meter still has obvious limitations.

Wrap Up:

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Ultimately, it’ll be interesting to see where this goes. I do love the concept of low-cost power meter accessibility. And perhaps more importantly, the ability for a consumer to quickly and easily just insert a power meter into their bike in a minute or so – all for $250. Sure, there’s the left-only limitation. But one of the things I’m ever-so-slowly warming to over time and doing years of power meter accuracy testing, is that I’m less convinced that on the whole power meters are as consistently accurate as people think and hope they are. And that for most people, even with slight shifting leg imbalances, I don’t think it’s as critical an issue. Certainly, there are use cases where it is – for example, aero testing just can’t handle those sorts of shifting tolerances. Or, bizarrely, whatever is happening this week for my leg balance on this specific bike.

In other words, looking at the larger the data sets of power meters and trainers I have over the last 10-12 years of testing 2-4 power meters on every single ride year after year, the more I’m coming to the conclusion that there are so many ways for power data to be inaccurate on any given day from any given vendor, that the left-only doubling thing probably is a wash in the end. Obviously, that doesn’t apply when a unit is 30-40w off, but when we’re talking sub-10w, that’s less precise as people might believe. That said, why on earth on this bike I’m seeing a massive left/right power difference is interesting.

Ultimately though, I like affordable access to power, and I like accurate power. Finding the right blend can be tricky. With that – thanks for reading, and more to come in the full review.

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58 Comments

  1. VJGoh

    For a power meter this price, I just want it to be sufficiently accurate, and I don’t care if it’s not perfectly accurate. I have a B-bike that doesn’t have a power meter, and if I could throw something cheap on it that could get me in the ballpark, that’s all I want. I’m willing to accept that and do most of my hard training on my bike with the spider-based power meter when I want to be sure that I’m getting the best numbers to analyze or send to my coach.

  2. Mayhem

    Do if one already had a Rival DUB crankset, the upgrade kit requires you swap out the spindle and hence the left arm too? Weird that they didn’t just make every Rival spindle (or even all Red and Force spindles too from now on) directly compatible with the power meter.

  3. Martin

    Why not test with other pedalsbased powermeters? To check if the difference remained the same.

    • From the review:

      “I will swap out the pedals for another brand/set on the next test. I was trying to aim for stability after the trainer test seemed to go well, and then obviously, things went not-well.”

    • Martin

      Ahh ok, missed that 😀 Great to hear.

      I would be using this mainly for Zwift Dual recordings, so accuracy is important in some sense. Interesting to hear more about the further tests.

  4. Am I right in thinking this will only work with a Rival AXS crankset – I can’t retrofit it to an existing non AXS Rival Crankset?

    • Geraint

      I’d be interested to know this too. At this price, if compatible with regular Rival, I’d buy one today.

    • j

      Same here, particularly for Force AXS DUB crankset. Based on past SRAM compat I’m gonna guess…no go.

    • Chad McNeese

      We need an official answer via SRAM but from what I can see, the crank arm hole to spindle interface sure looks similar to me. Maybe they changed shape and/or sizing just enough to keep them isolated, but we won’t know without info from SRAM.

      EDIT: Seems I may have found an answer on the SRAM site, and it looks promising.

      “Is Rival eTap AXS compatible with SRAM RED or Force eTap AXS parts?”

      “Many parts are cross compatible between SRAM RED, Force, and Rival eTap AXS such as: 12-speed Flattop chains, 12-speed cassettes from 10-28T all the way up to 10-36T, 1x cranksets, 2x cranksets (be sure to use the correct wide spindle crankset with the wide version front derailleur), shifter controls, and power meters. See the compatibility map on the service portion of the SRAM website.”

      link to support.sram.com

    • It’s definitely compatible with other AXS cranksets – it says that on the documentation. What I’m wondering though is if it is compatible with non-AXS.

      I’ve just bought a Ribble CGR SL with SRAM 1X Rival, and I also need to replace the crankset on my SRAM eTap (not AXS) TT bike

    • Ok further research I think the answer is no, for my case at least. Existing rival cranksets are GXP, new are DUB – wider diameter spindle.

    • The Rival AXS power meter utilizes a DUB spindle. Therefore any DUB drive side crank arm is technically compatible with this DUB non-drive side crank arm and power meter. In other words is you have a DUB crankset that is either RED or Force this Rival power meter will fit.

  5. Mike H.

    Not sure if anyone else is seeing this, but I had to refresh the article multiple times on Chrome because some add kept popping up in the middle of the screen and squeezing all the text off to the left side of the main content area.

  6. acousticbiker

    Thanks as always, Ray!

    I have a non-AXS Rival drivetrain on my gravel bike with Easton EA90 crankset and BSA bottom bracket. Would I be able to install the upgrade kit by simply replacing my current left crankarm?

  7. John

    This will be interesting for bikes without sufficient non-driveside chainstay clearance for even the skinniest crankarm-based powermeters (4iiii, Stages, etc.)

    It’s a shame these will only work with SRAM’s proprietary dubstep bottom brackets and Flattop chains/chainrings. At least it creates additional options for bikes with SRAM AXS Wide 43-30 cranksets.

  8. Barry

    It’s nice to see another lower price point option. The price of some of the recent SPD-based power meters was kind of shocking.

  9. Just a quick heads up to folks that I added another data set from another ride this afternoon into the accuracy section, which opens up a different can of worms. Well, two cans of worms.

    Cheers!

  10. John Tobin

    “More testing is needed, though, I suppose it does highlight the rare scenario where even if the accuracy is perfect, that a left-only power meter still has obvious limitations.”
    Except it isn’t that rare. In our household we’re two for two with left-only power providing junk numbers. There’s a thread on Slowtwitch with several posters documenting poor data from left-only meters due to leg imbalances. And the imbalance varies depending on power level, among other things. The guy that invented the Virtual Elevation technique, RChung, recently posted on ST that the single-sided power files that are sent to him have proven to be too noisy to use the technique.

    Quarq has a good reputation and we’ve had good luck with the three spider-based Quarqs in our household. But this device appears to be a step in the wrong direction.

    • Oh definitely – I’m fully in the power balance is variable camp. I’ve talked a lot about variations throughout a ride especially, and at differing power levels. But this sorta imbalance is crazy high. This isn’t 1-2%, or even 3%, it’s significantly more. I just had never considered bike sizing or fit to be a potential contributing factor here at a major level.

      And yup, Robert and I have talked at length about this topic before.

  11. Douglas

    Thanks for the review. Is this upgrade left crank als compatible with my force AXS Wide crank?

  12. The Real Bob

    I think you are right Ray, and I came to that conclusion long ago. Single sided power is enough from most cyclists other than specific use cases. I have a couple of 4iii single sided, Garmin Vector 3 duals, and a Giant dual sided. I use them all pretty much equal. While its cools to see the Vector pedal stuff and the individual leg power, its really not all that useful, but I am not a racer anymore. 3s Power and TSS type of stuff are enough. I really only got my first power meter for the training load stuff LOL.

    My question Ray is what does this do to 4iii? Their single sided power meter is 349? I think people would rather go for a major brand vs 4iii for the same price.

  13. Hicham QASMI

    It’s great news, but…

    Come on man, 125 EUR for a cassette,
    200 EUR per shifter. 125 EUR the rear derailleur. No backward
    compatibility with 11 speed. Fyi the current price of the 11 speed
    cassette is 40 EUR. An 11 speed rear derailleur is less than 75 EUR.
    That’s a huge jump!!!! Our wages is not increasing that much.
    I am a road racer, amateur. I spend hundreds, if not thousands in components
    per year with an average of 1 crash per year, and 99% of the time, as
    collateral damage because somebody in front of me got involved in a
    crash.

    I personally think it is unreasonable. And that’s why I am not moving to electronic 12 speed.

    This is bloody insane. SRAM is unintentionnally killing the amateur sports.
    We’re not all sucessful business people making 10,000 EUR per month with a
    budget of 10,000 EUR per year for cycling. The amateur cycling universe is supported by retired, low wage people. I hope SRAM will get that some day (that’s
    why the sport is dying faster is the US than in anywhere else).

    Don’t mistake me, I love SRAM gear: I think the mechanical shifting is superior to Shimano and Campa. I loved the cross compatibility across 11 and 10 speed (not need to change the wheel hubs nor the derailleur). All my gear is in SRAM. But, come on. Get a bloody graps of reality !!!

    No racing means no possibilities for passionate people, so, in the end, it means death even at the grass root level.

    This is basically a groupset to punish the normal people: only one leg only power meter, no compatibility with Force and Red. For all the power meters you bought so far that are 11 speed compatible: just throw them in the land fill. SRAM seems to be shameless. So now, only Campa and Shimano are offering cross compatibility in their 12 speed range. If I were extreme, I’d say this is bullshit. I am trying to understand SRAM, but come on, what’s going on here. This is at odds with their 10 years long practice of reusability and cross compatibility. How can anybody appreciate this in practice? (except if you ride only for 200 miles per year, which is understandable but not the majority of regular people)

    Hicham
    An inspired biker from Paris

    • I agree, if you’re looking to buy a groupset for an older bike and upgrade – it’s not gonna work out financially.

      But that’s not the market here. The market here is new bikes. SRAM says there are new 2,500EUR carbon bikes today with SRAM RIVAL AXS fully equipped. So full wireless on a carbon bike for 2,500EUR?

      I agree, replacement parts are silly expensive (as one who just purchased a 12sp cassette for this bike to put this on a trainer properly), but I don’t think one can imply this is for high end ridres only. After all, if you’re spending thousands per year already on replacement bike parts – that’s frankly way more than I ever spend on physical bike components per year.

  14. Leroy

    This sounds like a super enthusiast (aka red user) communicating to a bunch of other super enthusiasts (aka also red users) about how a product not intended for them, wouldn’t be good enough for them.

    I am not a big road rider but just being able to look at my left leg power week-on-week sounds like a pretty cool if I wanted to know I was getting stronger.

    I dunno, I guess I dont know enough about this to know if the data would still be useable. Can you put these parts on your bike and see how the comparison goes (if the test bike is too small)?

    • I’m hardly the guy who’s going to recommend buying top-end shifting or bike components. I think it’s mostly silly.

      I’ve written a lot on left-leg power over the years, though mostly within various reviews. In short, the challenge with left-leg power is that it’s not always consistent in terms of balance. Excluding this bike for a second, if you look at my daily riding and balance, I tend to be mostly fairly balance in my normal power range (roughly 200-315ish watts). Once I get above my FTP for sustained periods, I tend to see my power balance shift a bit. The same is true for when I get fatigued on much longer rides, it shifts. Interestingly, below my normal power range (easier pedaling), it also shifts.

      I did not at all expect to see that too small a bike it shifts, that was an extreme.

      All this matters because if your power shifts based on intensity, or some other factor, then it’s hard to do any comparisons.

      Now, my counterargument I was attempting to make above, is that I’ve seen enough power meters (all of them) have their bad days. And since I’m in the lucky position of knowing with 2-4 power meters per ride which one is having a bad day, then I can discard that unit for that ride. If I were someone with only one power meter, I suspect many of one’s PR’s might not be, and vice versa.

    • Hicham QASMI

      Hi Ray,

      I appreciate your post.

      On the dual side versus one side conundrum, here is my perspective and personal experience. Let’s say your ftp is 280w-300w (realistic for normal people below 50s year old). The best gain per year year could be typically 10 watts (in a real 20 minutes test for instance). That’s a 3%.

      Now most people on average have a typical imbalance from 1% to 2% between the right leg and the left leg (you can correct that with training but it is very hard and you need to be very patient, it takes years to correct that). Indeed, if you ever consulted a chiro or an ostheopath or a podologist, you have probably heard them saying ‘oh your other leg is longer than than this leg by 0.25 cm or less or more). So it makes sense. It also depends on your history and your natural imbalance. (personnally I am a former high level team handball player, left handed, with such an imbalance).

      The single sided power meter can be infinitely precise as much as it can, but it won’t change the natural body imbalance (about 2% typically for most people). So in the end, if you’re average, you cannot know precisely if you made progress on a yearly basis, because your progress lies in the uncertainty of the body imbalance and in your habit imbalance. The more fit you are, the less progress you will make, the less the single sided power meter will tell you. For this to make sense, you need also to keep in mind that your imbalance will also tend to be random, depending on your shape and on the cadence you ride at. I am not even considering people who like to measure their sprint power (by the way most strava segments are short and are about sprinting or efforts at vo2max …)

      So basically, single sided power meter are not much useful. I’d recommend for people who are not willing to think about this (this sounds like a headache I know…) not get a single sided power meter at all. Because the power meter won’t be able to measure where their fitness really stands.

      Hicham

    • I agree with everything you said.

      Except, I’m just adding that: In general, people put far too much trust in their power meters providing day to day accuracy. I’ve got great examples of super reputable units that just disagree on a random day for no reason: Quarq DZero vs Tacx NEO 2 or 2T spiking 3-5% different from any other day. Or a Favero Assioma pedal doing the same. Or a KICKR V5 doing the same. I can literally comb through all my data and find this for virtually every power meter.

      My point is that I don’t think, on the whole, the industry is yet to the point where one can assume that a PR day of 5w higher or even 10w higher is a legit PR. It just just be another random day in the power meter world.

      I’m not saying single-sided is the answer for everyone, but I am saying that the vast majority of people who say single-sided is useless, would probably be surprised to find out how quietly inaccurate their power meters and trainers are day to day over months/years.

    • Will

      You raise a good point about power. I think in this Zwift cycling era too much credence is given to power, W/kg or FTP as an absolute measure of everything. To the point where some might think you can declare your W/kg FTP at the beginning of a race and it will predetermine your result. For anyone who does TT outdoors will know that’s not the case. Day to day variation in yourself (fatigue, temperature, mental, etc) is far greater than any power meter accuracy issue is my experience.

    • ChrisTexan

      I’d consider there are 2 aspects (if not more) to the power meter utility.
      Item #1 is absolute training “fitness”… whether we agree on the state of the tech at this point, hopefully we’d all agree that the purpose for “status of fitness” purposes, is a consistent, reliable, output over time to see gains/losses, etc.
      For that perspective, dual-sided, and reliably accurate, is pretty much paramount (unless you are going from really unfit to really fit over time, in which case a few percent won’t matter until near the “really fit” end of the curve).
      I think for this, the argument against single-sided is pretty obvious, ignoring the other potential “variances” in any PM being discussed above.
      BUT for item #2, long-term, or even ride-to-ride, accuracy isn’t as paramount (but still important) AND single-sided is “goode enough”… and that is “during-workout” performance tracking/control. If your FTP is roughly 300, and you are doing a long ride, getting a bit tired, and not noticing that the elevation is slowly climbing, you might start going into the 310s, 320s, etc. If your goal is to hold a steady 290-300 range, single or double-sided will get that job done (again, assuming technical accuracy is reliable, not covering that).
      So for someone wanting to plan workouts/efforts around “power zones” and need a way to ensure they are staying in-zone, single or double isn’t critical, so long as it’s reasonably accurate (and you aren’t otherwise injured or have some overall issue like Ray has experienced here throwing off L/R balance in a major way). It’s a different use case.
      If you train all the time with a single-sided PM, balance doesn’t matter (again assuming nothing throws it off physically). Based on time spent training, you learn “when I ride above 300, I blow up after an hour, but if I ride below 280, I can ride for hours without problems” then single-side, double-sided, is irrelevant, you just need to know what you are doing in general to stay where you need to be for a given scenario.

    • Wouter

      I read  all the comments, but I could not get to a conclusion. All of the discussion about inbalance and the reliability of single sided power meter is leaving me with a  question.

      I am an amateur (ethousiastic bike rider) and I would like to see progress (or decline) in my power numbers. I do not care too much about absolute numbers in single rides, but is a single sided powermeter sufficient to see a trend over time? Or are the numbers too inaccurate for this purpose?

    • Will

      Yes, a single sided power meter is sufficient for most people to track progress.
      Even more so if you then use that power to moderate race efforts. Then it’s those race times together with power that you track.

  15. Matt T LeGrand

    Not sure why your numbers were off Ray. Sounds like you’ve had a rough couple of days. When I look at my secret footage of you on the bike, the bike seems to fit you perfectly: link to gph.is

    • Hahaha…

      I almost wrote ‘circus bike’ in the post, but decided against it. That pic is great!

      (To be clear, the bike is perfectly fine and nice, just perhaps not entirely my size – which, I’m 100% used to. In general, as long as the ride is under about 2.5hrs, I can usually ride just about anything no matter the size. Beyond that, it gets a bit tougher for me. I think for any bike industry person, it’s pretty much known that you might show up at an event and have a bike that’s not quite the right size. Shrug, a day on a bike is still better than a day not on a bike.)

    • andre

      That test bike looks pretty awesome in (polished?) aluminium and the carbon wheels. Probably a one-off for demo purposes to show off the colormatching SRAM stuff?

  16. ChrisTexan

    This may seem like a stupid obvious question, but if I don’t ask, I’ll always wonder (I haven’t read comments yet, sorry if it’s been asked already)…
    Are the crank lengths the same?
    As in, did you only replace the left-side crank with the PM crank? (or is it a full, hopefully matched, set?)
    If they sent you a 172.5 and you have a 170 or 175 on the other side, that would totally explain a significant left/right skew due to the leverage ratios for a spindle-based meter.
    Just a thought! If the PM assumes both sides match, and the drive side is providing more leverage (power ultimately if you are biomechanically “adapting” without realizing), you’d definitely see that at the pedals, but the PM can’t see it so assumes that left=right.

  17. Tyler

    My interest in power meters is maybe different than this product would allow, but I appreciate Ray and any other experts weighing in on this usage case.

    I have a right leg injury, and am mostly interested in a power meter, to potentially quantify and help me correct any pedaling imbalance. Primarily, to avoid/prevent injuries/strains from poor ergonomics on super-long (150 mile+) rides. But also, to potentially increase overall power.

    Do you think power meters (and their software) are good enough to assess this sort of thing, and coach me, in real time, to better form?
    If others have similar experience, I’m curious if total power output increases after addressing imbalances.

    I currently sort of relate power meters to HR monitors, while swimming: not enough real world data to provide actionable real-time feedback. But, maybe I’m wrong.

    Thanks for any and all info.

  18. Tom Kaufman

    This review — and the resulting comments — perfectly illustrate why Ray’s site is so good (and so helpful). Actual substance. It’s painful how rare that is in 2021. As I read all the other AXS “reviews” that came off embargo last week, most read like cut n’ paste from press release content, with a few others going a bit further and providing high-level commentary about the importance of bringing the price down on electronic shifting. But an actual substantive review with honest to goodness data about the quality of one of the more important parts of the release? Just here.

  19. Anne

    Did the power discrepancy get resolve? Maybe this is new technology and not strain gauge so it does not work well. Is the power measurement on the spindle or the left crank arm with the electronics inside the spindle?

    • Yes and no.

      One step forward, one step back. We think part of the discrepancy is that for whatever reason my legs on that bike are doing crazy balance things, likely due to fit (size of the bike). That explains one set, but not the last set, which shows that even accounted for that, there’s still a substantial gap.

      SRAM/Quarq is having me hold off on further PM accuracy testing as they can do some more digging. Which, is fair.

    • Anne

      What I am really curious about is if you know if power measurement is in the spindle or on the arm itself and the wires then go internal to the electronics. Is technology new or strain gauge? Very interested in this as my husband claims spindle is the best place for torque measurement and inline 6 engines are the best for balance. Neither one of us have ever had an issue with power balance so we no longer use left/right power and we would rather have a system dedicated to the bike rather than hassle with changing pedals bike to bike.

    • In the spindle, via strain gauges.

      I’m not sure one way or the other in terms of the ‘best place’ for power measurement at a technical level. I can say that in terms of total power, the spindle isn’t a good place, because it’ll only ever measure the left side. So while some people are perfectly symmetrical across all power ranges and any fatigue shifts, most aren’t from the data I see.

    • acousticbiker

      Any updates on this, Ray?

    • No updates yet, still on hold.

  20. Andrew

    Not sure if you’re inquired of this, but is SRAM able to provide a powermeter hub? If so you’d have three points to test off of.

    • Yeah, I don’t even know if it’s possible to build a PowerTap Disc XDR hub. I’m not enough of a bike mechanic to ensure all those pieces actually fit together or not. In theory, that was what the G4 that PowerTap previewed at Eurobike the summer before SRAM bought them, was for.

      I think in my non-bike-mechanic theory, I can take this:

      XDR: link to sram.com
      +
      Disc hub: link to sram.com

      Then add a 12sp AXS cassette, then build a wheel around it, then…magic?

      I honestly don’t know. Maybe someone here does.

  21. Alexander Hahn

    So, if this lovely Powermeter has Dub… is it compatible with my 12x GX-Eagle ode X01 MTB Crankset? Would love that Option for my XC-Fully 🤓

  22. Sue

    Thank you for this review. It has been helpful. I recently entered the gravel discipline after being a roadie for 30 years. Of course I wanted to track my TSS and watts on the gravel bike as I switch from trainer to road bike to gravel bike. Finding consistency across three different power meters and bikes has been challenging. My Stages crank arm based PM on my road bike is pretty accurate, as is my Tacx Neo Trainer… so when I got the gravel bike, I had 4iiii install a PM on my left 165mm crank arm. For months, the values coming from the 4iiii PM have been off the charts. I am able to ride zone 2 for and hour and get a TSS of 100 (and leap tall buildings in a single bound). So I consulted the engineers at 4iiii, sent them data files from all three bikes/PM sources and while there was a significant difference in the 4iiii values, their engineers maintain their unit is accurate. I am not sure whether it is because I ride a small bike w 165mm crank arms or if the 4iiii doesn’t jive with my Garmin 1030 but I had the PM removed/refunded and have been scouring reviews such as yours looking for the best solution for accurate/consistent power measurement. I have SRAM Force D1 DUB, 30/43 eTap on my gravel steed and the folks at SRAM have confirmed the RIval AXS Upgrade is compatible. I can not use a spider-based PM as my crankset is too small (43/30). Sadly the SRAM site says the Rival Upgrade Kit for $250 is not available until August 2021. My question is if they’re all essentially left crank-arm based PMs anyways, would I be better off with a Ralley 100 or 200 (which I can buy now for an arm or a leg) or wait for the Rival PM AXS Upgrade kit. When looking for accuracy, consistency, compatibility and just gravel bike power values, is it too much to ask that my PMs produce similar values across bikes and disciplines?

    • Paul S.

      Pretty much, yeah, it is too much to ask. Once the surface becomes rough, everything becomes much harder. Your power meter “feels” all of the forces on the crank/pedals, not just the forces that your legs produce. Somehow they have to filter out the noise that the surface produces from the signal that your legs produce. Is every PM manufacturer using the same algorithms to do this with the same parameters (or are they even doing this at all, since most PM’s are meant for paved roads)? And think about “pumping”, where mountain bikers produce a forward force using wheel sized scale corrugations in the surface they’re riding by shifting their bodies up and down (easy enough to figure out how this can produce a net forward force, not so easy actually doing it). The cranks aren’t turning, but a force is being produced. How is a power meter even supposed to measure that? So yeah, producing a power meter for gravel and mountain isn’t the same as one for pavement, and inconsistency is to be expected.

  23. Jpcopxc

    Would this crankset work on an 11speed? With the great price and smaller gear options this is the most attractive option out there for getting a power meter.
    Thanks

    • I’m still struggling to find a clear answer for this. I THINK that it will work (with a DUB BB of course). As the spacing is the same on an 11sp chain as a 12sp.

  24. Hannes

    Hey Ray, do you have any experience with a power meter in combination with an oval chainring? Does it affect the accuracy of the measurement? Greetings from Italy

    • Most crank/pedal-region power meters won’t “work” properly with oval chainrings. Physically they’ll work, but they don’t account for the math differences, and thus, they’ll inflate your power numbers, but it’s variable based on cadence.

      Favero claims too work (I haven’t seen independent any numbers one way or other other if it actually does), Power2max claims to as well (very non-confident in this claim). ROTOR does as well (very confident in this claim however).

    • Hannes

      Ok, thanks for the answer. then I better keep my „fun“ gravel bike free of those performance upgrades :/