Rotor 2INPower SL

The new Rotor 2INPower SL power meter is an update to its previous 2INPower meter. Rotor has reduced the weight and claims that its new SL is the lightest dual-sided power meter on the market. Its modular design is compatible with most current bottom bracket standards, it has demonstrated the ability to generate consistent, repeatable data, and with its long-lasting rechargeable battery, the system can compete with the best power meters available.

> Buy now: Rotor 2INPower SL for £880 from Sigma Sports

Our best cycling power meters buyer's guide rounds up our top 10 power meters.

Rotor claims it has reduced the weight of its new SL chainset by 15% compared with the previous 2INPower chainset. For 170mm cranks this translates into a 66g weight loss, thanks to the use of what Rotor refers to as its Trinity Drilling System, which is used to create the 7075-T6 crank arms.

In 2018 Rotor introduced its original 2INPower dual-sided power meter, which featured eight strain gauges – four in the axle and four in the driveside crank arm. In addition to this, Rotor also makes the INSpider, a single-sided power meter that attaches to the driveside of a Rotor chainset using the OCP (Optimal Chainring Position) system.

Compatibility

Rotor has kept many of the features of the original 2INpower, including the OCP. The OCP allows you to quickly and easily change the mounting position of the chainring or spider, which is especially beneficial if you use oval chainrings. Rotor is well known for its oval-shaped 'Q' chainrings, and Rotor says the OCP allows you to adjust the chainring 'to the precise point where you deliver maximum power during a single pedal rotation'.

> Power to the people! Why training with power is now cheaper and easier than you'd think

One of the big advantages of the Rotor setup is its versatility and the number of bottom bracket and chainring choices available to you.

It's available in four crank arm lengths – 165, 170, 172.5 and 175mm – which is comparable to SRAM Quarq and Shimano Ultegra and Dura-Ace, though doesn't go quite as short as some other Rotor crank arm options.

Weight

Rotor boldly claims that the 2INPower SL lightest dual-sided power meter on the market – more specifically, the lightest dual-sided power meter with a crank-mounted strain gauge and electronics in the spindle.

This being cycling, comparing its weight with that of its competitors is never going to be straightforward, as there are so many different power meter setups and locations available to us.

Our test model's crank arms and axle weighed in at 527g – 174g for the non-driveside, 353g for the driveside and attached axle. The 110mm x 4 spider added 51g, the 52T chainring 121g, the 36T ring 33g, with four chainring bolts adding a final 8g.

This makes an overall weight of 738g.

If you want to trim a tad more, Rotor's 52/36 direct-mount rings will bring the weight down to 695g.

The claimed weight of the Shimano Dura-Ace 9200 is 752g with 170mm arms and 52/36 chainrings, while the dual-sided Stages Dura-Ace 9100 weighs 745g with 172.5mm arms and 52/36 rings.

While SRAM claims to provide separate left and right power measurements, its Red AXS power meter, which is based on Quarq has a claimed weight of just 630g with 170mm cranks and 50/37 rings, is not a genuinely dual-sided power meter.

And then there are dual-sided pedal-based power meters. The Wahoo Powrlink Zero weighs 276g, the Favero Assioma Duo 303g and the Garmin Rally RS200 320g. With the Wahoo pedals, the cleat weight is also a factor, as they are heavier than Look or Shimano options. This compares with weights of 228g a pair for standard, non-power meter Dura-Ace SL pedals and 240g for a pair of Look Blade Carbon pedals.

So, is the Rotor 2INPower SL the lightest dual-sided option available today? Probably not. And if you wanted to keep weight down to the absolute minimum, you'd probably go for power meter pedals paired with a lightweight non-power meter chainset.

But the weight of the Rotor system is at least competitive against other axle-based dual-sided options.

Power measurement

The claimed accuracy has improved from +/- 2.0% to +/- 1.5% compared to the previous 2INPower version.

You can use the Rotor app to record rides with the usual measurements shown, including heart rate and GPS data. This feature will likely be of little benefit for riders using GPS head units, but the app does have other features, such as TORQUE 360, which displays your power across the entire 360-degree rotation. That said, the app did crash a couple of times and it didn't record the TORQUE 360 in a way you could look back on later, you could only see it real time.

If you do choose to use the TORQUE 360 feature it will likely mean an additional mount on the bike to hold a phone, or perhaps a more suitable option is to use it on a turbo trainer.

The app can also provide you with the ideal orientation for the OCP fit if you decide to fit oval chainrings.

The app does have a calibrate function, though you can still calibrate using GPS head units with calibration functions. It takes a little longer than with some other power meters, as you have to position the pedals vertically and hit calibrate, which will display a number – which should be 1,000. Then you rotate the pedals twice backwards and hit calibrate again. If successful you should see a number in the range +/-200.

Power reading and reliability

To test and compare the power meter reading I did several tests, both indoors and outdoors.

I initially tested this outdoors with Favero Assioma Duo pedals fitted, capturing the data simultaneously using separate head units. There was some discrepancy between the average ride power measurements, although crucially both tracked closely on any changes in power. The largest variance was a 4-5% difference, but for some rides there was almost no difference. Where there was a difference, the 2INPower SL reading was always the lowest of the two.

Moving indoors and testing on a Tacx Neo2 trainer, and still using Assioma Favero pedals, I was able to have a three-way comparison in a more controlled environment.

All three devices recorded almost identical data during a 25-minute interval session, both on average and at specific points. Just 2.1 watts – or 1.08% – separated the highest and lowest average power values.

The Favero Assioma Duo and Rotor 2INPower SL – the only true dual-sided options available – also recorded similar patterns for their L/R power balance, although it produced slightly different numbers, with the Rotor 2INPower SL showing a higher imbalance.

I do have a significant L/R imbalance while riding, so either figure could be correct.

It would be impossible to find out which of the three power meters was providing the truest value without a lab and calibrated gear – but when comparing the devices, data was recorded at levels that remained constant and within the claimed percentage range for both indoor and outdoor cycling during the entire test period.

If you have several brands of power meters on different bikes, it's possible these small variances may lead to problems if you're training towards extremely specific power values or a percentage of your FTP (functional threshold power), but this will always be a possibility if you're using different power meters even within the same brand.

The 2INPower SL uses a rechargeable lithium-ion battery housed inside the axle, which has a 250-hour stated battery life and a three-hour recharge time. Most other power meters, including SRAM/Quarq, Stages, and 4iiii use a disposable coin battery, but even compared to other rechargeable power meters, the Rotor's battery life is very good: Wahoo claims 75 hours for Powerlink, and Favero Assioma 50 hours.

The recharging point is hidden behind a rubber cap on the axle, though with the charging cable just a metre long you'll have to park your bike close to the plug or use a USB extension cable. However, given the battery life it's not as if you're going to be doing this very often.

You can rotate the rubber cap away from the recharging point or remove it completely to charge the battery, though if you do remove it, replacing it is a little tricky. And even if you do misplace it entirely, it still won't affect the unit's integrity, as it has an IP67 rating even with the cap off. This means it's effectively waterproof (including being submerged in water for up to 30 minutes) and is also protected against dust and sand.

I've been using the Rotor 2INPower SL for several thousand kilometres without issue, and it's still delivering reliable data. And given Dave's experience with the previous Rotor 2INPower, I've no doubt about its long-term reliability.

Value

The 2INPower SL costs £879 for the crank arms and axle, with extras such as chainrings or a spider on top. This price is slightly below the SRAM Red Quarq system even when chainrings are factored in, as this costs £1,187 while the Dura-Ace R9200 power meter that Liam reviewed is £1,199.99.

There are lower priced options, such as the latest SRAM Force at £772, while dual-sided options from Stages start from £875 for a Shimano Ultegra R8100 model.

The Favero Assioma Duo pedals retail at just £699 but Jack really rated them for their low weight and their ease of setup.

Anna Marie was almost as positive about the Garmin Rally RK200 Dual-sensing Power Meter pedals, which are now £869.99.

Rotor's single-sided INSpider spider-based power meter that I tested a couple of years ago costs £611 but when you factor in an axle and Rotor ALDHU aluminium crank arms, you're looking at close to £940, which makes me think the new 2INPower SL is better value.

Conclusion

The biggest benefit with the new 2INPower SL is the reduction in weight, which'll save you around 66g depending on the length of the cranks. Other advantages of the system are that you can of course use your own pedals, and the super-versatile modular system is designed to work with a huge range of chainring options – including Rotor's own oval rings – as well as pretty much every bottom bracket standard out there.

And while lower weight isn't an issue for all of us when it comes to a power meter, accuracy and durability are. The battery life is excellent, the whole setup feels durable and it has delivered consistent data that I feel I can trust all the time.

Verdict

Genuine dual-sided power meter with a versatile modular fit that delivers consistent data – and with a very good battery life