In The Know Cycling

Choosing the best power meter for you and me as road cycling enthusiasts is now easier than it has been in years. Prices have stabilized, performance has equalized, and options have normalized.

Our road bike power meter decision essentially comes down to how much beyond $/£/€300 we are willing to pay for installation convenience, pedal preference, model compatibility, or power data geekery. Based on those criteria, I’ve found that the best competitively performing and widely available options are power meters in pedals from Favero, Wahoo, and Garmin, on crank arms from 4iiii and Stages Cycling, and on crankset spiders from Quarq and Power2Max.

At the same time, using a power meter has become broadly accepted by roadies as a key to enabling us to ride faster, a status traditionally held by a new bike, wheelset, or other gear that typically costs far more than a cycling power meter does.

While I still want to know all the deets when a cycling friend gets anything new, I know I’ve got to be on my game when a fellow enthusiast shows up for a ride with a power meter on their bike.

In this review, I’ll tell you more about how road bike power meter products are maturing, how to pick the best power meter for your needs and preferences and give you my reviews of the best power meters that fit them. (Click on any of those phrases to go directly to the part of the post that covers that topic.)

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ROAD BIKE POWER METERS HAVE MATURED

In the second half of the last decade, the number of companies jumping into the road bike power meter business with proven, unproven, or announced but undeveloped models tripled the handful that competed for business before then.

Many consumer market booms these days are driven by a new design or application of technology that yields a considerably lower-priced product and reaches untapped demand many times larger than was currently being served.

In the case of power meters, Stages Cycling was the first to put a strain gauge sensor on the left side crank arms of popular Shimano crankset models back in 2013. They sold them for just under $1000 or between 2/3 and 1/2 the price of the best-selling SRM and Quarq power meters that were bolted to the crankset rings (a “spider”) or Powertap models that went inside the rear wheel’s hub.

By doing so, Stages power meters reached the occasional road racer and nerdier end of the enthusiast road cycling segments. These were far larger, more consumer-oriented groups than the pro, triathlon, and top-category amateur racers who were the primary buyers of cycling power meters before, mostly to give their personal coaches the data to improve their individual training programs.

Seeing Stages’ success, many companies both experienced in the cycling market and new to it jumped in. These companies introduced, or at least announced, power meters that used strain gauge sensors on crank arms and spiders and in new places, including pedals, bottom-bracket axles, and even inside shoes.

The relatively lower prices of most new cycling power meters drove those making long-established models to drop their prices once the new entrants proved their technology worked and saw their sales grow.

More roadies bought these new and lower-priced established models and learned how to use them to improve their performance without needing a coach. As there was apparently a lot of profit to be made, the hype machine spun quickly, and new price drops attracted more cyclists, retailers, new models, updates, performance claims, analytical features, etc.

And then, about five years after all of this new product and market energy started, things began to calm down, sort out, and consolidate.

While still growing and certainly not old, the road bike power meter product market seems like a maturing young adult leaving behind a pretty wild time of adolescence.

Specifically, I see that:

Options have normalized: As in any maturing market, road cycling enthusiasts have had enough time to focus on a shorter list of power meters and suppliers that best suit their budget, performance needs, and preferences. Those that don’t have broad appeal have either been marginalized or exited, either through acquisition or getting out completely.

For example, rear hub power meters from Powertap, the company that made what was once considered a benchmark location and product for measuring your power output, are now gone from the scene. SRAM’s Quarq power meter unit bought the company, perhaps to use their greater retail distribution power and engineering resources to revive the brand and its fledgling product line, but have now discontinued the Powertap hub, pedal, and spider products.

For a variety of reasons, the Powertap products and others that tried to get in or stay in were not competitive in the maturing power meter market.

With three at the start and after a boom of 15+ companies introducing power meters, seven companies now serve most road cyclists.

Direct force or strain gauge-based road bike power meters are now only made for pedal, crank arms, and crankset spider locations. And as I noted in the introduction of this post, there are only two major suppliers of power meters for each of these locations.

Others, including SRM, Verve, Specialized, and Rotor, are smaller or niche power meter suppliers either because of their prices, design, performance, or distribution.

Remaining dealer inventory and outdated websites notwithstanding, Easton, Pioneer, FSA, Team ZWatt, Polar, and Watteam have stopped making power meters. Ashton Instruments, Xpedo, Limits, Luck, and untold others announced products that never made it into production.

Shimano, obviously a major player in the cycling drivetrain components business, does make a dual crankarm power meter they include on some of the pricier bikes equipped with its Dura-Ace groupsets. SRAM also includes their Quarq power meters on expensive bikes that are included with some of their gruppos.

Unlike SRAM, Shimano currently appears more interested in using its power meter as a profitable OEM upsell opportunity for the high-end bikes it goes on rather than as another standalone product to sell in the aftermarket. Shimano’s aftermarket products are typically competitively priced, have a differentiated, patented design, and are widely distributed. Their power meter has none of these attributes.

New iterations of existing models will certainly come out over time. Quarq, or another power meter or cycling industry supplier, may add a new product for a location where they don’t currently make one, likely in a pedal power meter.

The cost and complexity of power meter development in a market that has already seen tremendous price compression make me think it’s very unlikely there will be many successful new models coming from companies that don’t already make technically proven, well-accepted, and profitably priced power meters today.

SRM, one of the original power meter suppliers and not to be confused with SRAM, is now making the X-Power pedal system based on Shimano’s SPD mountain bike platform. Notably, this is a different power meter pedal than the overpriced and hard-to-calibrate SRM Look Exact based on the Look Keo road bike platform.

Garmin now makes the Rally series power meters that add the Shimano SPD SL road bike and SPD mountain bike pedal platforms to the Look Keo one they already make (reviewed here). The Rally is essentially the same Vector power meter they made before, only rebranded for a wider range of pedal types.

Favero, which also started with a Look Keo power meter pedal called the Assioma, now makes the Assioma Duo-Shi for SPD SL pedals (except the Dura-Ace). Again, it’s the same power meter they’ve been making all along, adopted for Shimano pedals.

Wahoo followed with the POWRLINK ZERO based on the Speedplay pedal platform.

Performance has equalized: Power meters are often marketed around their accuracy. Claims run between +/- 2.0% or +/- 1.0%. If you are a road cycling enthusiast producing 300 watts, that 1.0% difference is  +/- 3 watts. That amount doesn’t matter to anything other than your bragging rights and is easily overwhelmed by a dozen other things that could affect how much power you can translate to the road, from your wheel’s stiffness to chain lube to you getting a better night’s sleep.

Power meter consistency, or getting the same reading day after day for the same power output, is more important than the absolute accuracy of your power meter readings. However, I’ve not seen power meter suppliers make claims about their product’s consistency.

Fortunately, there have been a lot of evaluations of the actual performance of power meters done by independent testers and publications I trust. The differences they show in the accuracy, consistency, drop-outs, top-end power, temperature compensation, communication to your head unit, and other measures of the best power meter models from the leading companies are nearly non-existent or so small that they shouldn’t matter to almost all road cycling enthusiasts.

I realize I’m taking a risk in speaking for all of my fellow roadies with that last italicized statement. Note that I’m not talking about pro or Cat 1 and 2 road racers or time trialists, triathletes, track cyclists, or their personal coaches. But frankly, I think there are probably many things that are more important to their training and performance, even for them, than these small differences between the best power meters.

There are differences in battery life, another performance measure, and how you recharge or replace your battery, a feature more than a measure. There are also some differences in reliability. I’ll say more about these things in the reviews below.

This is probably as good a time as any to remind you that you want to zero-offset nearly every power meter at the beginning of each ride and certainly when you transfer it between bikes regardless of the type of you are using. If you don’t, there’s no guarantee that it will read your power consistently.

It’s easy. Put your bike outside in the temperature you’ll start your riding in while you put on your shoes, gloves, etc. Turn on your head unit, move cranks or pedals into the prescribed horizontal or vertical position, and push the zero-offset button on your head unit or let it calibrate automatically if your can do that. Within a few seconds, the zero-offset is done and start your ride.

Acceptance has been realized: Once thought to only benefit high-level racers, cycling power meters are now accepted as standard equipment by those who want to train better, ride faster, manage their efforts more efficiently, and do inside rides on Zwift. That means serious amateur cyclists like you and me. 

The best power meters have moved well beyond an analytical aid for personal coaches. As more roadies use training tools and programs like Zwift, TrainerRoad, SYSTM, FasCat, and others (see my training plan review) that track their progress on Training Peaks, a power meter has become accepted as an essential training tool to measure your progress and guide your daily and long term plans.

Do two or three 6-week training blocks well with the help of a power meter, and you could increase your average or normalized power output during a ride by 10 to 20 watts or more. This would allow you to ride faster or save energy at the same speed. That amount of increase is comparable to the drag saving you’ll get from an aero bike or deeper set of carbon wheels at a far lower cost.

When you know what power you can hold for 1, 5, 20 minutes, and longer, you can also use your energy on rides and in events more efficiently. You can monitor how much energy you burn overall and at key parts of a ride. And once you know this, you’ll know how many and how hot to burn those metaphorical matches you have during challenging sections of a route.

A power meter set up on the bike you use for inside rides or built into your smart trainer has also become the tool you need to calculate your power-to-weight ratio. More so than speed or heart rate, your power-to-weight ratio is key to picking out the right Zwift group rides and measuring and managing your efforts during any ride in Watopia and other virtual worlds.

If you are new to training with power, here are two books I’ve read, continue to refer to, and highly recommend. Hunter Allen and co-author Andy Coggan wrote Training and Racing with a Power Meter, which laid the foundation for much of what everyone is doing now with power. Friel wrote The Cyclist’s Training Bible, the original and still the best resource I’ve ever read on endurance training. Friel’s newer book Fast After 50 is for those of you who want to keep improving despite your age.

Unnecessary features have been neutralized: There’s been an argument from some reviewers and suppliers that determining your power by adding how many watts come from your left and right legs is better than measuring your total power from what they produce together or doubling what one leg produces.

While it’s certainly interesting to know how much power each leg generates or their relative strength, I’m unaware of any training prescriptions that come from having this knowledge for riders with normal power imbalances despite having this analytical capability in some power meters for 5+ years.

Unless you are coming off an injury, most riders will have an imbalance somewhere between 55/45 and 45/55. Few will produce 50% of their total power from each leg and a 2% variance is very common. That seems perfectly normal since our legs are usually not exactly the same length and few of us are “ambipedal” or use our right and left feet and legs equally.

While I’m not privy to what some private coaches may be telling their high-level athletes, I’ve not heard or read of training guides, fitters, or power meter suppliers suggesting that you do something different in your bike or strength training, bike or shoe-fitting, or anything else to even up your power output.

No doubt, it’s interesting to know that you might have a 2%, 3%, or even 5% imbalance. But, recognize that you’ll pay nearly twice what you would in the initial purchase price for a pedal or crank arm power meter to have this information that you physically won’t do anything with and may mentally obsess about.

While not comprehensive, my discussions with stores selling road bike power meters show a clear preference for pedal and crank arm power meters with a single sensor that measures and doubles the power you produce from your left leg.

To a lesser degree, other proprietary analytical features built into Garmin and other bike power meter software have been neutralized except for the geekiest enthusiasts or Garmin-centric among us.

Pioneer’s crank arm power meters were differentiated around some very cool-looking pedal stroke and other analytical features. As I mentioned earlier, they’ve left the business. I don’t know how much their feature strategy played a part in their success or lack of it, but it certainly didn’t save them.

As best I can tell, none of the six leading power meter suppliers successfully depends on proprietary analytical features to separate themselves from the others.

Prices have stabilized: As you might expect from any mature business, power meter prices have stabilized. Only six large-volume power meter suppliers remain, of which two make pedal power meters, another two make crank arm ones, and two others make spiders.

Starting prices went down in the last decade from about $1500 to $1000 to now between $300 and $600 for road bike power meters made by the six. The other suppliers exited the business or have remained in lower-volume niches usually with higher-priced products.

With demand continuing to grow and after all of this sorting out and consolidation leaving two major suppliers competing for each power meter location, I think it’s unlikely we’ll see more price declines until demand flattens out or shrinks. Indeed, save for the occasional sale at a specific retailer, I haven’t seen notable price drops in this decade.

HOW TO PICK THE BEST POWER METER FOR YOU

If you’ve been waiting for lower prices or fewer choices, or a better understanding of how a road bike power meter can improve your speed and performance, you probably haven’t been alone. But, with the market maturing in the ways I described above, picking the best power meter for you and your needs has become much easier.

With little to no difference in how well road bike power meters perform, choosing between them comes down to how much extra you are willing to pay for a shortlist of things that may be more or less important to you.

Those things are:

* Price – You don’t need to spend more than about $/£/€300 for a power meter that will give road cycling enthusiasts all we need to get the performance benefits of training and riding with power. As you’ll see below, there are several reasons why you can and, depending on your needs and preferences, might want to spend more, but that $/£/€300 amount is the price floor today.

* Installation convenience – If you ride one bike, then a left-side crank arm power meter is the least expensive way to go. If you have more than one road bike where you want to use your power meter, power meter pedals are the easiest kind to move from one road bike to another.

Want to move your power meter between your road and gravel bikes? A crank arm power meter is your least expensive option. Unless you never plan to put your foot down in the dirt or gravel off-road, you don’t want to use road bike pedals. Even if you have a Shimano GRX gravel crankset on your gravel bike, it uses the same left crank arm attachment fittings as on Shimano road groupsets.

* Pedal preference – If you use Shimano and Look pedals, Favero’s Assioma or Garmin’s Rally power meter pedals will suit you and be the most convenient power meter to move between road bikes. Wahoo’s POWRLINK power meter pedals meet the needs of those that prefer Speedplays.

All of these come at a price premium to a single-sided crank arm power meter.

If you prefer TIME or another road or gravel pedal model, then go with a left-side crank arm power meter as the lowest-priced option and the next easiest one to move between bikes. Dual-sided crankarm and spider power meters are more expensive and take more work to switch from one bike to another.

* Model compatibility – Power meter pedals work with any crankset. There are zero compatibility issues with power meter pedals.

Most enthusiast-level road bikes have Shimano cranksets, and most others have those made by SRAM or Campagnolo. Both Stages and 4iiii sell Shimano crank arms or cranksets with their power meters installed on them. Only Stages sells SRAM, and Campy crank arms with power meters pre-installed, and only for some of their crank arm models.

However, Stages and 4iiii will install their power meter sensors on some of your own gear rather than buying a new crank arm or crankset with their installed power meter sensors. While you’ll have to be without your gear for 2-4 weeks, this can keep your cost down and give you the option to get a power meter on brands of many other road crank arms that you wouldn’t otherwise be able to.

Acceptance among enthusiasts has led to a wide range of compatible solutions.

Spider power meters also require that you use a model compatible with your crankset. Quarq, owned by SRAM, focuses on SRAM cranksets but doesn’t offer much for owners of Shimano and other brand cranksets unless you want to change out your crank arms and bottom bracket.

Power2Max, the other major spider power meter supplier, sells spiders that don’t require you to add new arms for many more brands than Quarq but not for Shimano due to the big S’ unique design.

Velocomp makes a power meter you hang on your handlebars and is, therefore, as compatible as pedal power meters. However, it uses measurement technology that can provide 5% or greater variation in your power meter readings if you regularly change positions on your bike, as most of us do. Further, it costs around $300, the same as the least expensive crank arm power meters. For those reasons, I don’t recommend it.

* Power data geekery – If you want to totally nerd out on power data, you’ll probably want left and right-leg independent measurement capability that is only possible from power meters with sensors in both pedals or crank arms.

Spider power meters give you total power and have an algorithm to estimate L/R metrics based on how you torque the spider during your pedal stroke. While I’ve found the calculated balance is within 1-2% of what you’ll get from independent measurement over the course of a ride, it’s not a true L/R measurement for those of you that insist on it.

There are various pedal balance, efficiency, and “smoothness” analytics over different time intervals you can measure if you have L/R power measurement.

Favero Assioma pedal power meters also provide Garmin’s Cycling Dynamics suite of metrics captured exclusively on Garmin head units. They can show you things like how much time you spend standing vs. seated, how much power you are putting out in each part of your power stroke, and where your power is distributed across your pedal.

It’s all very interesting data that may excite the geek within us. However, we cannot do much with this data other than perhaps become obsessed with it. And it costs more to feed that part of our habit.

And yes, I have independently left/right power meter cranks. But, after a few summers of reviewing and playing with them, I’ve found worrying about a percent or two difference between my left and right leg is a major distraction to my training focus and the pleasure of riding my bike. I do nothing differently with that knowledge and nothing in the Cycling Dynamics suite that would influence my training.

I will note that some enthusiasts have a power meter but don’t train to any kind of plan that uses it. This renders their power meter a worthless and expensive toy. Don’t be that guy or girl.

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REVIEWS OF THE BEST POWER METERS

As I wrote in the opening of this post and detailed in the sections above, no performance differences should matter to most road cycling enthusiasts between the six market-leading and widely available road bike power meter options.

Instead, you should choose among them based on how much beyond $300 you are willing to pay for installation convenience, pedal preference, model compatibility, or power data geekery.

Below, I’ll review the leading pedal, crank arm, and crankset spider bike power meters against those criteria.

Other cycling power meters made for roadies either serve more narrow groups of enthusiasts or are higher-priced or both.

PEDAL POWER METERS

Favero Assioma Duo (left), Garmin Rally RS200, Wahoo POWRLINK

A power meter built into a road bike pedal is the easiest to install and transfer between bikes. It is also compatible with any road crankset a cyclist might own. This makes pedal power meters like the Favero Assioma among the most attractive options for enthusiasts who want to use a power meter. This is especially the case if you have more than one bike or different model cranksets on the bikes where you want to measure power.

And while there’s no significant performance or training benefit or prescription for roadies from measuring and analyzing independent left and right power sensor data, power meter pedals are equipped to do so in ways that fewer crank arm power meters outside Shimano ones can and that spiders can only estimate algorithmically.

Favero makes the dual-sided Assioma DUO-SHI power meter spindles to use with your own Ultegra or a handful of lower-tier Shimano road pedals for about US$660/£8780/€600. You replace the spindles on your current Shimano road pedals with the spindle and attached power meter pod that comes with the Assioma DUO-SHI.

If you already own Shimano pedals, the Assioma DUO-SHI is about 2x the price of the least expensive, left-side only 4iiii and Stages crank arm power meters or the cost to have their sensors installed on your own left crank arm.

They aren’t made for Dura-Ace pedals and aren’t sold with a single or left-side-only option.

The Assioma DUO-SHI has a wider spindle than the one it replaces in your Shimano pedals. With a width or “Q-Factor” from the outside edge of your crank to the centerline of the pedal of 65mm, it’s about 10-12mm wider on each side than most pedals or power meter pedals.

This difference was much discussed and me-thinks incorrectly judged negatively for the DUO-SHI when it first came out. Fitters I’ve talked to estimate that over half the riders they’ve worked on, especially those that are tall, have large feet or have tight hip flexors from sitting in an office chair day after day need spindles longer than the common 53-55mm Q-factor of other power meter pedals.

Placing Shimano, LOOK, or Speedplay cleats more inside or outside on your shoes can give you up to 5mm more or less width than setting them right in the middle. So the effective ranges are more like 50mm to 60mm for most and 60mm to 70mm for the DUO-SHI.

This short video segment from a Peak Torque review of the DUO-SHI explains this in more depth.

Oh, and if you also ride a gravel bike or mountain bike, know that cranksets used on those bikes already push your feet out much more than the 10mm or so difference you’ll get with the cleats placed in the middle of the road shoes you use with these power meter pedals.

If you are uncertain about what Q-factor is best for you and whether that should affect your power meter pedal choice, I encourage you to talk with your bike fitter. Your knees will thank you, and your power output will be more efficient (aka higher) with the right width.

Favero also makes the Assioma UNO US$495/£450/€440, which are Look KEO-style pedals that have a left-side-only power meter pod attached to their spindle. At that price, it is 50% ($150) more expensive than the lowest-priced crank arm option.

If you want Look KEO pedals with left and right sensing power meter pods, Favero sells the Assioma DUO for US$760/£595/€690. These are more than 2x the lowest-priced crank arm option and also more expensive than the DUO-Shi option for those of you who have Shimano road pedals.

Favero’s Assioma DUO-Shi and DUO power meters become price competitive against higher-end Shimano crank arm power meter models, and those made for SRAM and Campagnolo crank arms. They are also less costly when compared to spiders, where you have to add some combination of crank arms, chainrings, or bottom brackets to make them compatible.

Garmin’s single-sided US$650/£580/€650 Rally RS100 (Shimano) and RK100 (Look) power meter pedals are over 2x ($350 more) the price of buying or putting a sensor on your Shimano crank arm. They are also slightly more than the dual-sided Favero Assioma DUO-Shi and not much less than Assioma DUO. At US$1100/£970/€1100, the Rally RS200 (sensors on both sides) is 1.5x to 2x the price of the dual-sided Favero Assioma models.

Again, if you don’t have Shimano pedals, you need to buy them for the Assioma DUO-Shi. The Shimano Ultegra PD-R8000 pedals, the highest level and most expensive ones that work with the DUO-Shi, cost US$200/£133/€129 through these links to Competitive Cyclist, Power Meter City 10% off w/code ITKPMC10, Planet Cyclery, Merlin, and Tredz 10% off w/code ITKTDZ10. These are all stores that I recommend because they have very competitive prices, top customer satisfaction ratings from fellow cyclists as reported by independent services, and a great selection of gear for road cycling enthusiasts.

Even if you add in the cost of these pedals, the Assioma DUO-Shi are better priced than the Rally pedals.

As with the Garmin Vector, the Rally uses a coin cell battery accessed by a battery door. Poor seals on the Vector models led to high-reliability issues reported both by users and dealers. In my testing, Garmin has solved this problem with the Rally.

While the Rally’s claimed battery life is roughly 2 to 3 times Assioma’s 50 hours, the Rally requires a less commonly available button cell battery. By contrast, you can recharge your Assioma batteries at the same time you recharge your head unit, lights, or electronic shifting batteries.

With the introduction of Wahoo’s POWRLINK ZERO in February 2022, Speedplay pedal loyalists finally have a power meter to call their own. Like Favero’s design, the POWRLINK power electronics sit in a pod on the spindle between the crank arm and pedal itself.

At US$1000/£850/€1000 for the dual-sided POWRLINK and US$650/£550/€650 for the single-sided version, it is priced similarly to the Garmin Rally power meters. Battery life is a more-than-ample 75 hours, and, like the Favero, they recharge using clip-on power cables. The POWRLINK gives you the power and cadence data you need but doesn’t calculate the suite of pedal-specific metrics that Garmin and Favero do but that no one knows what to do with.

While a couple of trusted independent testers had access to it for 6-12 months before launch, most of us are just getting our initial season of experience with it. The POWRLINK performed well – accurate and consistent – on my test rides and those of the longer-term testers. Wahoo has proven its power measurement experience from its smart trainers and has significantly retooled the Speedplay line and manufacturing facilities since acquiring the business. This makes me hopeful, but still waiting to verify its long-term reliability over the course of several seasons.

SRM started selling its first-generation EXAKT Look KEO-based pedal power meter in 2018, but it is far higher priced than the Assioma and has been shown to give inconsistent power meter readings in independent testing. SRM appears to have moved on from this joint project with Look and is now focusing on a new SPD mountain bike power meter pedal system but it’s very, very hard to find at stores.

Powertap, purchased by Quarq, stopped making power meter pedals in 2020 after a couple of generations of models that didn’t perform as well or weren’t as price-competitive as Favero’s.

With Favero and Garmin giving you both Shimano and Look power meter pedal options and Wahoo offering a Speedplay one, most of us roadies can now find a competitive power meter pedal solution to suit our pedal platform preference.

But, if you don’t have a pedal design preference and are attracted to the ease of installation and universal compatibility that pedal-based road bike power meters offer, I recommend the Favero Assioma UNO (Look) or DUO-Shi (Shimano) for its superior price and proven long-term reliability. If you are a Garmin fan but don’t want to pay the premium, I suggest getting a crank arm power meter.

I’ve written a dedicated review of power meter pedals if you want to go into more depth.

To order the Favero Assioma power meters, you can click on these links to Competitive Cyclist, Power Meter City, Amazon, and others in Know’s Shop, all stores I rate highly for their competitive pricing and customer satisfaction.

The Garmin Rally is available at these links to Competitive Cyclist, Planet Cyclery, Power Meter City, Tredz, and Know’s Shop.

You can find and order the Wahoo POWRLINK ZERO at these links to Competitive Cyclist, Power Meter City 10% off with code ITKPMC10, and Tredz 10% off w/code ITKTDZ10.

CRANK ARM POWER METERS

4iiii (left) and Stages Cycling power meters

For as little as US$300/£299/€342, left-side crank arm power meters from 4iiii and Stages Cycling give you the lowest price options to ride with power while still giving you all the performance and metrics most road cycling enthusiasts would ever need.

While their claims differ, actual differences in their accuracy, consistency, battery life, or other performance measures are hard to see from tests conducted by independent parties. Even with the differences that probably do exist, they are so small or insignificant that they are unlikely to affect your training and performance.

4iiii and Stages Cycling have been making power meters for years and have become very reliable after several model iterations. They use readily available CR2032 coin cell batteries and last 100+ hours, in my experience.

Installation and Transfer: While not as easy to install and transfer as a pedal power meter, crank arm power meters are easier to set up than a spider power meter.

Here’s a video on how to replace a left-side crank arm and an entire crankset. As an enthusiast with no wrenching experience and indeed never having changed a pedal, crank arm, or crankset myself before getting my first power meters, I can assure you this is all quite doable in short order.

It is also wise, and I’d highly recommend using a small torque wrench when fastening your left crank arm. This ensures you don’t over- or under-tighten your crank and, equally important, that it doesn’t move around on you. After installing or transferring, you should run a zero offset like every day before you ride, even if you don’t make any changes.

Most crank arms tighten with less than 15NM (clearly noted on the crank arm), requiring a much smaller, very portable, and inexpensive wrench.

Measurement and Analytics: With power sensors on both your left and right crank arms, you can get independent power measurement, pedal balance, efficiency, and “smoothness” analytics. But, if you want to fully geek out on the Cycling Dynamics metrics, you’ll need a Garmin Vector or Favero Assioma pedal power meter.

Pedal Preference and Model Compatibility: Crank arm power meters also don’t limit your choice of pedals the way a pedal power meter does.

However, there are limits to the range of models that crank arm power meters are compatible with beyond Shimano cranksets, the most widely used ones among roadies.

And that crankset model range is probably the biggest difference in choosing between a 4iiii and Stages power meter.

Depending on the crankset model, you can buy a crank arm or crankset with power meter sensors already pre-installed on them or send the crank arm or crankset you already own to 4iiii or Stages to have the sensors installed at their factory.

Both companies sell Shimano 105 ($300), Ultegra ($350), Dura-Ace ($450), and GRX 810 ($350) cranks with their power meter sensors pre-installed to one or both of the arm’s inside surfaces.

I do recommend 4iiii and Stages left side crank arms for Shimano groupsets. However, I don’t recommend right side Shimano crank arm power meters from 4iiii, Stages, or anyone else supplying them including Shimano. There is something about the design or manufacture of the newest Shimano Ultegra and Dura-Ace models that independent testers have found produce inaccurate power meter readings.

Stages also sell left-side only crank arms with the pre-installed power meter sensors for SRAM BB30, GXP cranks, and  Campagnolo Chorus, Record, and Super Record 11 and 12-speed models. These sell for a good deal more than the Shimano ones, with SRAMs running $500-$570 and the Campags ranging from $600 to $850.

If you own one of the more common Cannondale, FSA, or Easton models, Stages also makes pre-installed left-arm power meter cranks for some of their models.

Now, if you can part with it for a few weeks, you can get one of their power sensors factory installed at 4iiii or Stages onto your own left-side crank arm. And it will only cost you $300 to do so regardless of whether you own a 1st, 2nd, or 3rd tier of Shimano, SRAM, or Campagnolo.

Both companies will also factory install sensors on some Cannondale, FSA, and Praxis left arms you may own.

If you want sensors factory installed on both crank arms, 4iiii will do it for $500 on the same range of Shimano cranksets I listed above (but I don’t recommend it for the right side Shimano arms) plus some SRAM, Campy, FSA, and Praxis cranksets. Stages will factory install dual-sided sensors for $550 on the three road groups.

You can click on these links to see the complete list of crank arms and cranksets that Stages and 4iiii (left, right, both) will factory install their sensors on.

You can get a 10% discount on 4iiii products when you link to one of my top-ranked stores Power Meter City and use the exclusive code ITKPMC10 for In The Know Cycling readers. They are also available using these links to Merlin, and Tredz 10% off w/code ITKTDZ10, and others in Know’s Shop, all stores I recommend.

For Stages power meters, order using these links to stores I recommend including Competitive Cyclist, Power Meter City, 10% off with code ITKPMC10, Merlin, Tredz 10% off w/code ITKTDZ10, and others in Know’s Shop.

SPIDER POWER METERS

Power2Max (left) and Quarq power meters

Spider power meters that bolt onto your chainrings are one of the original power meter designs. Because of their design longevity, spiders are often viewed as a power meter benchmark, have been improved to provide amongst the highest accuracy rates, and are available for a wide range of crankset models.

Road, time trial, triathlon, and track racers, along with traditional roadies of all stripes, often favor spiders for their proven record over many years of experience.

Power2Max and Quarq power meters serve the broadest range of road cycling enthusiasts and crankset models with the most competitively priced products. They are both highly reliable.

Others you may know – SRM and Shimano – make significantly higher-priced spider power meters that serve smaller customer groups. Still others – FSA, Team Zwatt, and PowerTap no longer make spiders, though you may still see some for sale.

A spider can be the best, cost-competitive solution to fit your current drive train situation and how you intend to use a power meter. You’re a good candidate for a spider if you plan to focus your power meter measurement principally on one bike, already have a crankset model that only requires you to add the spider to get you going with power, don’t much care about independent leg power measurement or pedal stroke analytics, or want to use your preferred Shimano, Speedplay, Look, Time or other pedal models.

If some of those situations don’t describe you, a pedal or crank arm power meter will likely be a less costly and more suitable way to go. Here’s why.

Installation and transfer: A spider power meter takes a little more work (though not a ton) to install than the other types. If you’ll be using it mostly on one bike, not a problem. Install it yourself if you are handy and have the tools. Have a friend or shop install it if you’re not.

To move your power meter spider between bikes, you’ll need to move the entire crankset, similar to the way you would one with power meter sensors on both crank arms. It’s certainly doable but it will take 15-20 minutes out of your riding time to make the switch and clean up once you get good at it. This compares to 5-10 minutes to switch your pedals or left crank arm. The video in the section above on crank arms shows you how.

You’ll also need to have the same bottom bracket on any bike you want to put your power meter-equipped crankset on.

Price: Since a spider or spider power meter connects the drive-side (right) crank arm to the chainrings, it is made for specific crankset brands and, sometimes, models. Depending on your crankset, you may only need to buy the spider. That’s the least expensive solution and can cost no more than US$400-$500

To put a Power2Max or Quarq power meter on your bike, you may need to change out your crank arms. With some, you’ll also need a different bottom bracket and/or chainrings. That can boost the price to between US$600 and $800 or more and leave you with an entirely new crankset that doesn’t perform as well or look as integrated with your groupset as the ones you replaced.

Model Compatibility: The need to change crank arms is why Power2Max and Quarq power meters are not a great solution for Shimano crankset owners. Shimano now makes its own crankset power meter for Dura-Ace and likely Ultegra models in the future. SRM has long made a Dura Ace spider power meter. However, both a far more expensive than a dual pedal or crank arm solution.

Instead, spider power meters are typically more cost-effective if you have a SRAM crankset or one made by Specialized Cannondale, Rotor, FSA, Easton, or Praxis.

Power2Max makes spider-only power meters for the widest range of cranksets including those who already own many Rotor, SRAM, Cannondale, or Specialized cranksets and won’t need to change their crank arms. These sell for US$490/€490 and up for their NGeco models that claim 2% accuracy and use a coin cell battery that should last you an entire year before needing to be replaced (400 hours). You don’t get estimated left/right power balance or pedal smoothness with the NGeco spiders but for $50/€50 each, you can buy a software upgrade that will give you that data.

For twice the price, US$940/€990 and more depending on the model, you can get a Power2Max NG that claims +/- 1% accuracy, gives you faux left/right balance, pedal smoothness, and torque efficiency data, and a rechargeable battery that goes about for a season (150 hours) between charges.

Both lines of spiders can also be delivered with new crank arms for FSA, Rotor, Easton, and Campagnolo cranksets.

You can get Power2Max products when you link to one of my top-ranked stores Power Meter City. They are also available at the company’s online store here.

Quarq, owned by SRAM, has a more SRAM-centric product line. They make spiders for the full range of SRAM’s newest electronic Red and Force 2x and 1x AXS groupsets and their older mechanical Red and Force and cranksets.

Beyond a spider power meter made specifically for those of you with Specialized S-Works carbon cranks, Quarq takes a more agnostic approach than Power2Max in serving other crankset owners.

Rather than try to fit their spider to your cranks, Quarq sells you the spider along with their Quarq or SRAM cranks. While their non-AXS spiders alone are competitively priced at US$399, you’ll need to add roughly US$200 to $400 for Quarq, Force, or Red level crank arms if you don’t already own a SRAM crankset. And, if you don’t have one, you’ll also need a DUB or EXP bottom bracket (US$40) to go with those cranks.

Quarq’s DZero (5-bolt) or DFour (4-bolt) spider power meters fit the chainrings used in most of the leading cranksets that you may own. You can also add rings to go with these spiders for another US$180.

It’s a modular approach that starts competitively but gets more expensive if you don’t own SRAM cranksets. But, Quarq’s long track record of performance and reliability, and its large footprint at SRAM dealers make it a solid option if a spider power meter is a good solution for your situation.

Pedal Preference: If you have a strong pedal preference, and it’s not for the Look Keo design, the spider power meter doesn’t limit you in the way the Favero or Garmin power meter pedals do.

Measurement and Analytics: A spider power meter measures your total power rather than adding your left and right power (dual pedals and crank arms) or doubling your single-leg power (left-side pedals and crank arms).

After all, there’s only one spider, and it’s bolted to the chainrings and torqued at a given cadence by both crankarms and pedals to produce a power reading.

Instead, Quarq and P2M road bike power meters use algorithms to estimate your left and right leg power balance. They promote “dual-sided power metering” and “separate left-right power balance” even though they don’t measure it directly from power meter sensors from the left and right sides.

Some reviewers say these spiders mirror true independent leg-measuring power meters in side-by-side tests, while others say they don’t. My experience riding simultaneously with the spider, dual-side crank arm, and pedal power meters shows a 1-2% difference in the estimated and measured left/right power balance values after 1-2 hr long rides on various terrain.

This is one of those po-ta-to vs. po-tah-to differences that shouldn’t result in, as the lyric goes, deciding to call the whole thing off. For me, the reasons I’ve reviewed above are more important ones when deciding whether or not to buy a spider power meter, unless your inner geek tells you otherwise.

Through this link at Power Meter City, you can also get an exclusive 10% discount on Quarq power meters using the code ITKPMC10. They are also available using these links to the following stores I recommend: Competitive Cyclist, Planet Cyclery, Merlin, and others in Know’s Shop.

* * * * *

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Thanks, and enjoy your rides safely! Cheers, Steve.