THE BEST POWER METER FOR YOU

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 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 ARE MATURING

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 the need for a coach. As there was apparently a lot of profit to be made, the hype machine spun up quickly and new rounds of price drops attracted more cyclists, retailers, new models, updates, performance claims, analytical features, etc.

And then, about 5 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 and 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 and Powertap, the company that made what was once considered a benchmark location and product for measuring your power output, are both 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.

Power meter options have normalized

With 3 at the start and after a boom of 15+ companies introducing power meters, 6 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 powermeters. 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 built with their Red gruppos.

Unlike SRAM, Shimano currently appears more interested in using their 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.

The cost and complexity of power meter development in a market that has already seen tremendous price compression make me think it 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.

More recently, Garmin introduced their Rally series power meters that adds the Shimano SPD SL road bike and SPD mountain bike pedal platforms to the Look Keo one they already make. Favero, which also makes a Look Keo power meter pedal, will likely add SPD SL and SPD ones as well. Wahoo has also announced a Speedplay power meter they plan to introduce this summer.

As a fan of the Shimano pedal systems and an avid user of Speedplay pedals, I’m looking forward to testing out the new SRM, Garmin, Favero,/ and Wahoo power meter pedals and seeing the results from other independent testers. But knowing how good companies with strong engineering teams have struggled out of the gate with power meters, notably Garmin, Shimano, Look, and Polar, I’m tamping down my excitement for these new power meters until they’ve been ridden a few seasons.

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 put translate to the road from your wheel’s stiffness to chain lube to better 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 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, or track cyclists or their personal coaches. But frankly, I think there are probably a lot of 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. Within a few seconds, the zero-offset is done and start your ride.

Acceptance has been realized: Once thought to principally 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.

The best power meters have moved well beyond an analytical aid for personal coaches. As more roadies use packaged training programs like TrainerRoad, Sufferfest, FasCat, and others 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 are capable of holding 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 are burning 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. Freil’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 not aware 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 or power meter suppliers recommend 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 business that is maturing, prices of power meters 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 a whole lot 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 us 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 don’t have a strong preference for one of the major road pedal types, Favero’s power meter pedals based on the Look Keo pedal platform will suit you and be the most convenient power meter to move between road bikes. Garmin has just recently introduced a Shimano SPD-SL power meter pedal and Wahoo is developing one based on the Speedplay platform but neither have been thoroughly tested by independent sources I trust or have been through a couple of seasons of field testing.

If you prefer Shimano or Speedplay to Look, and I rate Shimano higher and have had good luck with Speedplay pedals prior to their new owner Wahoo’s update, 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 side crank arm and spider power meters are more expensive and take more work to switch from one bike to the next.

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

A majority of 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 from them with their power meter sensors already installed. 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.

Stages crank arm power meters

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 alas, 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 pedals 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, there’s not a lot we can do with this data other than perhaps become obsessed about 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 summer of reviewing and playing with them, I found it more productive and time-efficient to leave the right crank on my primary road bike and use the left on my gravel bike.

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, there are no performance differences that should matter to most road cycling enthusiasts between the six market-leading and widely available road bike power meter options.

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

 

Power meter criteria comparison

 

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

Power Meter Pedals

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

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 is what makes pedal power meters like the Favero Assioma amongst the most attractive options for enthusiasts who want to use a power meter. This is especially the case if 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.

For US$460/£449/€514, the Favero Assioma UNO pedals with a left-side only power meter is 50% ($160) more expensive than the lowest-priced 4iiii and Stages crank arm power meters or the cost to have their sensors installed on your own left crank arm.

Favero’s Assioma UNO and DUO power meters (sensors in both pedals) become price competitive against higher-end Shimano crank arm power meter models and those made for SRAM and Campagnolo crank arms. They are 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 US$650 Rally RS100 (left-side sensor) power meter pedals that use the Shimano SPD-SL pedal platform is over 2 times ($350 more) the price of buying or putting a sensor on your Shimano crank arm. At US$1100, the Rally RS200 (sensors on both sides) is 1.5 times ($380 more) the price of a dual-sided Favero Assioma.

The Rally power meters were also introduced only in March 2021 and have yet to be fully vetted by independent testers or by users over a couple of seasons in the field.

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. It will be interesting to see whether 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.

Wahoo’s Speedplay POWRLINK power meter pedals are not available to consumers yet (projected “summer 2021”) and haven’t been priced or vetted by independent testers or regular cyclists. 

SRM started selling its first-generation EXAKT Look KEO-based pedal power meter in 2018 but it is far higher priced than the Assioma has 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

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.

The Favero Assioma is based on the Look KEO pedal design. Some roadies (myself included) have a strong preference for Shimano or Speedplay road pedals which in my comparative review perform better and give you more fit options than the KEO.

If and until the new Garmin (and likely Favero) SPD SL and promised Wahoo Speedplay pedal options pan out, not having power meters based on those platforms offset a lot of the advantages of the pedal power meters for roadies who favor them.

But, if you don’t have a pedal design preference or are attracted to the ease of installation and universal compatibility that pedal-based road bike power meters offer, I recommend the Favero Assioma for its superior price and reliability. If you are a Garmin or Speedplay fan and can hold off until they are proven or don’t want to pay the premium, I suggest getting a crank arm power meter.

To order the Favero Assioma UNO or DUO, you can click on these links to Power Meter CityAmazon, Wiggle, and others in Know’s Shop, all stores I rate highly for their competitive pricing and customer satisfaction.

The Garmin Rally will be available at these links to Power Meter City, Competitive Cyclist, Planet Cyclery, and Tredz.

You can read my more detailed review of power meter pedals here.

CRANK ARM POWER METERS

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 have any effect on 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 shop 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 this, to use a small torque wrench when fastening your left crank arm. This assures 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 same as you should 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) and this requires a much smaller, very portable, and inexpensive wrench like this one available from Wiggle.

Torque wrench set for crank arms

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.

There are limits, however, 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 sells left-side only crank arms with the pre-installed power meter sensors for SRAM BB30 and 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 3 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 ITK10 for In The Know Cycling readers. They are also available using these links to Merlin, Tredz 10% off w/code ITKTDZ10, Chain Reaction Cycles, and others in Know’s Shop, all stores I recommend.

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

SPIDER POWER METERS

Spider crank arms

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, they are made for specific crankset brands and sometimes, models. Depending on what crankset you have, 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 spider power meter

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 a 10% discount on Power2Max products when you link to one of my top-ranked stores Power Meter City and use the exclusive code ITK10 for In The Know Cycling readers. They are also available at the company’s online store here.

Quarq power meters

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 their 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 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 ITK10. They are also available using these links to the following stores I recommend: Competitive Cyclist, Tredz 10% off w/code ITKTDZ10, and others in Know’s Shop.

 *     *     *     *     *     *     *

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First published on February 15, 202. Date of the most recent major update shown at the top of the post.

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23 comments

  • This is a really great summary!
    In my experience, any leg imbalance is quite consistent for a person. Since single sided power meters actually double the watt of your one leg, to estimate the power of two legs, a 3% L/R imbalance at 300W starts out being 9w but is then doubled to 18w, which could be a problem. That’s why 4iiii have a great advantage compared to Stages, because 4iiii allows you to adjust the ‘scale factor’. So if you have the possibility to compare your single side crank arm power reading to a smart trainer (consider drivetrain loss), you may calculate the imbalance, adjust the scale factor (in this case 0.94) and have the 4iiii report corrected numbers!

    • Henri, Thanks for your kind feedback and for adding the tip on the 4iiii scale factor.

      To follow up on your example, even if you don’t adjust your power meter for the imbalance, is there anything you would do differently with a reading of 282 vs. 300 watts or a 3% known imbalance as long as those readings are consistent? While you might feel better about yourself with an 18 watt higher reading (even though you are producing the exact same power), what if I or a mate told you that your power meter consistently reads 2% higher than others? At least for now, and after 5+ years of having independent L/R measurement capability, I’ve not read or heard about different training approaches because of small imbalance or even the suggestion from credentialed coaches that you should strive for a balance. And as long as your power meter reads consistently and your L/R balance is consistent, you should do the same training and get the same benefits of training with any of the power meters I’ve reviewed above.

      Good news for us roadies, there are many other things that have a real effect on our power output and speed that we can worry about! 🙂 Training program, aero position, shaved legs, chain friction, etc. Any of those will keep us busy for a long time. Cheers, Steve

      • Hi Steve
        You’re right, power number precision (repeatability) is relevant and accuracy is not so much.

        Only exception is when mixing different devices. In in my case, mixing indoor workouts (smart trainer measured power) and outdoor workouts (power meter).

    • Henri,

      Great comment regarding 4iiii’s scale factor. I was a former Stages left-side only user and it always seemed that my power output was too low compared with my performance. I switched to Assioma dual-sided pedals 2 years ago and of course they proved that my left leg was the weaker one, thus under-reporting my power.

      But here’s where it gets interesting. You state that leg imbalance is quite consistent for a person. In my case, I have found the the disparity between legs increases with effort. Typically for moderate efforts I am L/R 46/54. If it stayed that way across all efforts I could shrug it off. But for light efforts I am at 48/52, or even 50/50 if I focus on my form. But at the other extreme, I did 10 minute efforts at threshold earlier this year and my balance was a disturbing 41/59. My data over the course of the last few years proves this again and again: the harder I go, the greater the disparity. So I am wondering if anyone else with dual-sided power has experienced this, or whether it should be addressed. (Bike fit? More strengthening of the left leg?)

      Steve, thanks so much for another extraordinarily researched and informative post! I really appreciate it.

      Also to add 3 more advantages of dual-side power meters:
      1. Can do single-leg drills on the trainer. (Stages not only would not record, but would pause the workout. Pedaling right leg only was as if I had stopping pedaling)
      2. More accurate for shorter efforts, since there is twice the data for a given time. Useful for sprinting.
      3. If you are competing on Zwift, your power/weight ratio will be more accurate (if you have a significant leg disparity)

  • Hi Steve,

    Interesting read, I very much appreciate your sorting all this out. WRT buying & using a PM, I’ve been resisting while many biking friends push me (gently) to get a PM setup. Perhaps not your intention, but just having this of setting the zeroing meter before every ride convinces me not too bother. Getting out for a ride is already complex enough. Anyway, like many riders, especially us older guys, I carry about 15# extra weight & nothing I could do training wise would make as much difference as dropping the weight, so that too.

    Best,

    Ron
    BTW, there are a number of typos in the article. For instance, “…about 5 years of all this new product…” which I assume was intended to read “…about 5 years after all this new product…”. No biggie to me. But if you’d like, I’ll send you a few other edits as well.

    • Ron, If it makes you feel better, Favero and Quarq have updated their firmware so that once set, you don’t need to zero offset unless you transfer the power meter. And, my personal experience as an old guy is that a power meter, training, and weight loss make up a virtuous triangle. Using a power meter made my training easier/better and caused me to lose weight.

      And yes, I’d welcome your input on typos and edits. (send to:[email protected]). My eyes get a bit glassy after writing, reading, editing, over and over as I put these reviews together over weeks to the point where I can’t see it anymore. Thanks! Steve

    • Ron,
      I built up a bike last summer and bought a Quarq Dfour spider power meter and it works great. Best feature, no calibration or zero-offset required before you ride. Problem solved!
      -Kyle

  • What about IQ2?
    Did I miss seeing it?

    • Andre, IQ2 is a current example of a power meter that, like many that never made it during the boom years, was announced, redesigned a year later (from a crank arm to a Look KEO pedal power meter), has missed shipping date goals, is not yet in production, has not had production units independently tested on the road for performance and reliability, but sounds terrific if it ever delivers as marketed and priced.

      Check back in a year. They may or may not be able to deliver on what they are working on. Unfortunately, too few companies new to power meters have been able to do so. Steve

  • Brilliantly clear article – quick question. My road bikes are all Ultegra and gravel bikes Shimano 105. If I were to buy an Ultegra model of either the Stages or 4iiii left crank power meters is there an issue switching between the Ultegra and 105 cranksets?

    • David, nope, none at all. I’ve transferred a left Shimano power crank arms among Ultegra, 105 and GRX cranksets. The Shimano crank fittings are all the same. Steve

  • Do all the options support using their own proprietary head unit or sending the data to a smart phone? I’m trying to figure out the best way to consolidate the visualization of data while riding.

    • Whitman, none of the six I’ve reviewed use proprietary head units. Use standard cycling GPS head units that read ANT+ and BLE like one of these from Garmin or Wahoo. And while some recreational riders do, you really don’t want to put your smartphone on your bars (too big, not crashworthy, battery hog, not purpose-built, need apps, limited functionality, etc.). Steve

  • Hi. Really enjoyed the article – informative, detailed and (mostly) fact-based. Nevertheless, a couple bones to pick with regards to the non-factual bits:

    1) you wrote: “More roadies bought these new and lower-priced established models and learned how to use them to improve their performance without the need for a coach”. IMHO power-meters don’t render coaches unecessary (and I’m not one). If anything, coaches are even more necessary, given the diferent metrics that now come into play (TSS, ATL, CTL, IF, etc). Not having a coach – or a very deep understanding of how to use these metrics when drawing a training plan in their absence – may mean that the power meter istelf will end up being used as the most expensive speedometer in the world.

    2) I would add “Customer Service” as one of the key components when deciding which power-meter to go for. To be fair, this is not something that you alone left out of the equation. I almost never see it on reviews. And yet, no rider wants to be left waiting months on end for the issue(s) with his power-meter to be dealt with (and all of them have their issues).

    Still, as said before, great overall job.

    • Maximilian, Thanks for your kind and constructive feedback.

      Regarding coaches, I agree that power meters don’t render them unnecessary. It’s more like coaches aren’t absolutely necessary to do good training as they were before. Now, if you’ve got a training plan or subscription from one of the better services and Training Peaks to track your progress, you can use a power meter to follow the plan guided by all the metrics you mention. Yes, the plans are written by coaches but they don’t require you to have them on retainer and customize the program for you. Certainly better if you can afford it, but not necessary. I write about this in the Acceptance has been realized section further down. Reading the Hunter Allen and Andy Coggan book that I mention in that section will also tell you all about those metrics.

      On customer service, I agree with you. I haven’t researched this rigorously and wish I could for all the products I review. Reading through comments on forums and at the end of other reviews and talking with a few retailers about their experience with some of these power meters didn’t pop up persistent reliability issues or an unusually high return rate beyond (beyond the Garmin pedals which I cautioned against) or customer service complaints. I know, not the best way to measure this but that’s about all that’s available unless I did a more rigorous study.

      3-4 years ago, this was a bigger problem with the power meters. All six of the ones I’ve reviewed here have been around long enough to have resolved prior issues (e.g. Stages battery doors) they may have had with product iterations (except Garmin). If there were still reliability or service issues, I think we’d be hearing about it. Some that couldn’t resolve their issues have left the business for this very reason. Cheers, Steve

      • Maximilian Leisner

        Thanks Steve. I have not only read Hunter’s book, but also attended one of his camps in the US and promoted two others :-). This one still is, as you mention, the go to book for anyone interested in learning more about power meter and all the metrics involved. My comment regarding the need for a coach is that, based on the athletes I have been around (i.e. have sold units to and/or trained with), those who elect to forego the coach end up looking at the numbers on the computer’s screen as if the readings alone would make them perform better. But you are right about the online coaching platforms. They help bridge the gap, so to speak. Cheers.

  • Hey Steve
    Great article! I want to buy a power meter and crank arm type looks best for me, but I have a Cannondale SuperSix Evo with a cannondale crankset (the rest of the components are Dura-Ace). Do you know if these crank arm meters will work with a Cannondale crankset? Don’t do any research for me. Just wondering if you know.
    Thanks much

  • Hi Steve,

    I’m a big fan of your work! I learned a lot from your articles, especially on rims and tyres. Am waiting for my 50mm (24mm inner width, hooked) gravel wheels to be delivered from Farsports I ordered with help of your articles.

    I really want to take training a step further then the HR zones related training I’ve done over the last few years. Read Friels’ bible and love it.

    I ride a 2019 Trek Checkpoint SL6 Di2 with the Ultegra R8000 groupset. The Checkpoint has no room for a left crankarm based PM, I ride mtb spd pedals so basicly the only option (if I want to keep the slick Shimano crank looks) is to go for right arm only PM. I like the 4iiii and don’t care to much about the exact measurements as it is for my training only. But I do want and need consistency in the measurements

    That’s where things might go wrong…. there seems to be a significant problem with PM on the right crank arm with (only) the Shimano Ultegra and Dura Ace models.
    Your work is always super in depth so I am surprised not reading anything in your article about these issues. Or did I just miss it?

    The whole issue is explained in great detail by GP Lama (link below). I am very curious about your opinion about this!

    I hope you find time to answer this soon as I am about to send my crank from The Netherlands for a ‘cosmetic surgery holiday’ to Canada ?

    And keep up the great work with the wonderful reviews you guys are making!! ??

    BR,

    Paul

    https://gplama.com/2019/06/29/shimano-crankset-power-meters/

    • Paul, Thanks for your comment. First, I have never reviewed and do not recommend Farsports gravel or road wheels.

      As to the power meter, I am familiar with the GP Lama report that you site. This report broke some new ground in their testing approach and findings. Other independent reviewers using different protocols didn’t find similar issues with the Stages and 4iiii power meters they had tested. More recently (as in since I first published this review), Ray at DC Rainmaker reported a similar issue with the 4iiii model but has been less than definitive about the Stages right. Whatever is causing the issue, it seems to be confined to the right side only of the latest 8000 Ultegra and 9100 Dura Ace models. So I’ve now updated my review to recommend the left side only power meters for those who have Shimano cranksets. I’ve not seen anything about the 105 and GRX right side power meters but I’d err on the side of caution and recommend against their right side power meters as well. I’ve always recommended most enthusiasts only need a left side power meter anyway.

      For your situation where you can’t fit a left-side power meter and use MTB SPD pedals, you’ve probably seen that Garmin has introduced the Rally XC100 and XC200 MTB SPD power meter pedals. They are pricey and I’ve just now gotten a pair to begin testing, but that’s an option. SRM makes one as well but it’s even more expensive and the jury is still out on their performance. Another option would be to go with the left side Favero Assioma Uno pedals and buy yourself a good pair of road shoes. You’d still come out ahead after buying the shoes. 🙂 Steve

      • Hi Steve,

        Thank you for your fast reply!

        I never intended to suggest you recommended Farsports wheels. Your articles about all the different aspects of a carbon wheelset really helped me make my own decision. I just wanted to share the outcome of that decision, just fyi.

        Thx for the tip on the Garmin new pedals, I was not aware! Way out of budget though, I considered buying vector 3’s with the RC kit but no go either.

        I am trying to get some quantification on how bad the ‘4iiii right only’ option would be for my training, am just an amateur enthousiast who rides apr. 200km/week and a few cyclos each year.

        If the 4i option means my measurements will be within a 5-10% variation I think the influence on my actual training would be neglectable.

        The video off the former 4i/Garmin PM engineer on the GP Lama site suggests the variations could run up and over 25% theoretically, that’s kinda scary but (hopefully) not very likely…

        I’ll dive some more into it, thanks for your help!

  • Steve, long time reader and user of your reviews. Your testing and research convinced me to go tubeless on my BMC Roadmachine. I also followed your lead and upgraded to the ENVE 3.4 AR wheelset. I am now in the process of buying my first gravel bike and following your lead with a Giant Revolt. Although speced with GRX the crankset is a Praxis. My road bike has a Stages LH power meter (Ultegra crankset) which is very reliable. Stages does not offer a power meter for Praxis cranksets. Did you swap out your crankset for a GRX to accommodate a Stages? There are other options (pedals or spider based) but all have long backorders. Thanks for all you do. Joe

    • Joe,

      Thanks for your confidence in my recommendations. Glad they’ve worked out. Feel free to support our ability to keep doing what we do by buying through the links on the site.

      I did get a GRX crankset to replace the Praxis on my Revolt and then put a 4iiii left side 105 crank arm on it as my groupset is a 105 as well. But you can get a power meter installed on your GRX 810 crankarm through the factory install programs with a pretty quick turnaround. Power Meter City can set you up for Stages through this link and 4iiii through this one. They also offer In The Know Cycling readers a 10% discount on 4iiii. Use the code ITK10 at the checkout screen. Steve

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