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by Matt Wikstrom
November 7, 2014
Quarq has been refining its crank-based power meters since 2006. The company’s latest road crank, ELSA RS, features a four-bolt spider specifically designed for Shimano chainrings. In this review, CTech Editor Matt Wikstrom takes a closer look at what the ELSA RS has to offer.
Quarq was founded by Jim and Mieke Meyer in 2006. At the time, the couple were living in Australia, and in between triathlon training sessions Jim started working on a crank-based power meter design that would be more affordable than SRM’s system. He also wanted a system where the battery could be replaced in the field.
Quarq unveiled its first power meter at Interbike in 2007. From the outset, Quarq used strain gauges in the crank’s spider to measure torque and the original CinQo was designed to suit a variety of cranks. Aside from easy battery replacement, the CinQo was distinguished by its early use of ANT+ for wireless transmission of power data.
SRAM acquired Quarq in 2011 with Jim appointed as Technology Director. The company continues to operate in Jim’s hometown of Spearfish, South Dakota where all manufacturing and development are carried out.
Quarq’s range of crank-based power meters currently comprises four models for the road and one for off-road use. The major difference between each model is the design of the spider, which varies to suit different chainring sizes and patterns. The ELSA RS crankset is the company’s latest offering, which utilises a spider with a four-bolt pattern to suit Shimano 11-speed chainrings, and for the first time, incorporates active temperature compensation to further improve the accuracy of the power meter.
The ELSA RS is supplied as a crankset with a pre-installed battery, a selection of magnets, a pair of washers for the pedals, and a quick-start guide. There is a choice of three lengths (170, 172.5, or 175mm) and two axle types (SRAM’s GXP or BB30) with a recommended retail of $1,900 (GXP) or $1,950 (BB30). However, buyers will have to supply suitable chainrings, a compatible bottom bracket, and an ANT+ device before they can start measuring their power output on the bike.
The ELSA RS crankset is designed for Shimano’s 11-speed four-bolt Hollowglide chainrings. The four-bolt pattern allows compact (34/50T), mid-compact (36/52T), and standard (39/53T) chainrings to be interchanged, making for greater flexibility than the five-bolt patterns used by Quark’s other road cranksets, though the chainrings are expensive (at least $200/pair).
For those buyers swapping out cranks with either with a GXP or BB30 axle, no more hardware will be needed and installation will simply be a matter of sliding the right crank and axle into the bearings (and spacers/wave washers) and attaching the left crank arm. For those using a different axle (e.g. Shimano’s 24mm axle), a suitable bottom bracket will have to be obtained and installed, adding at least $50 to the purchase price. It is worth noting that the ELSA RS is not compatible with some bottom bracket standards such as BB386.
Quarq does not supply a head unit with the ELSA RS but recommends Garmin Edge 500, 510, 800 or 810 devices. Any other ANT+ enabled device (including an iPhone with an ANT+ adaptor) can be used to view and record power data from the cranks. For those buyers that don’t have a compatible device, they will have to spend at least another $100 to get started.
When added together, the extra costs make for a total upwards of $2,250. When CyclingTips founder Wade Wallace first reviewed Quarq’s CinQo Saturn power meter in 2011, the local retail price was $2,300 sans ANT+ device, so little has changed in Quarq’s pricing even as the company has updated and improved upon its power meter technology.
Five strain gauges are positioned in the spider of the ELSA RS to measure torque. By comparing measurements for the downstroke and the upstroke, the system can also report the balance of power between the right and left legs without directly measuring the output of each leg. In doing so, some assumptions are made, and the system cannot report power measurements for each leg like the systems from Pioneer and Garmin.
Cadence is crucial for the calculation of power by crank-based power meters. The magnets that are supplied with the ELSA RS crankset are designed for the cadence sensor in the spider, which comprises a series of reed switches.
Interestingly, Quarq also installs an accelerometer in the cranks for measuring cadence. It’s a curious redundancy, however excess vibrations (think cobbles) will interfere with the accelerometer, so Quarq recommends installing a magnet and using the reed switches for the greatest accuracy. Under these conditions, Quarq claims the accuracy of the ELSA RS is ±1.5%.
The strain gauges employed by the ELSA RS are very sensitive and susceptible to changes in temperature. In the past, Quarq has relied on passive temperature compensation based on the predicted (rather than known) effects of temperature on the power meter. In developing an active temperature compensation system for the ELSA RS, Quarq directly measured the effect of temperature on the power meter by collecting over 10,000 data points for temperatures from 0-130°F (-17 to 54°C).
It makes for very sophisticated calibration of the power meter that the system refers to as it measures the temperature for each pedal stroke. As a result, Quarq claims the ELSA RS boasts the most accurate and precise power meter it has ever manufactured.
The ELSA RS has a sampling frequency of over 3,500Hz that is packaged in 60Hz macro-samples and averaged for each discreet pedal revolution. The result is that, at a cadence of 90rpm, data is sent to the recording device every two-thirds of a second. There’s no need for faster sampling though as ANT+ devices can only record and display data once every second, plus there’s little value in real-time power measurements.
The carbon crank arms of the ELSA RS are constructed using SRAM’s Exogram technology. Each arm is hollow, providing some weight loss, while the broad cross-section improves stiffness, making for an attractive strength-to-weight ratio. I neglected to weigh the crankset sent for review but according to SRAM, an ELSA RS crankset with a GXP axle weighs 616g; fitting Dura Ace 9000 chainrings will add another 141g.
The ELSA RS is powered by a CR2032 battery that has a promised life of around 300 hours, is widely available, and cheap to replace. Accessing the battery is simply a matter of unscrewing the cap with the big Q on it and while this is supposed to be a tool-free operation, I needed to use a set of pliers.
Quarq warns against the use of tools as they can damage the compartment, so heavy-handed home mechanics should take extra care when it comes time to replace the battery. A cap design that was easier to grip would solve this problem altogether.
Finally, the ELSA RS has an IPX7 waterproof rating, which means it is resistant to immersion to a depth of one metre for 30 minutes. For more information on the ELSA RS, visit Quarq for details on the cranks, FAQs and product manuals.
Installing the ELSA RS crankset was no more difficult than any other crankset, and aside from ensuring a compatible bottom bracket was installed, there were no special precautions or considerations. Shimano’s HollowGlide chainrings were also easily installed, though home mechanics will need to have a set of Torx keys on hand for the bolts.
Installation of the cadence magnet is best done before the cranks. Three styles of magnets are supplied with the ELSA RS crankset: one is fitted to a ring that is compatible with threaded bottom bracket cups, another is attached to a slotted fork that will slide under a standard bottom bracket cable guide, and finally, there are a couple of buttons that can be mounted on the frame with putty.
The magnet needs to be mounted 2-8mm from the spider of the cranks in line with the marked sensor zone. Quarq’s online manual provides plenty of guidance, however there is no convenient readout (like an LED) to confirm that the magnet is doing its job.
There is a LED situated in the spider of the cranks that provides information on the status of the power meter. Back-pedalling a few times activates the power meter and the LED will flash, unless the battery is dead. More than one flash indicates an error in the system.
Putting the ELSA RS to work was a very simple matter. As described above, all that was required was to activate the power meter and pair it with the ANT+ device. After that, the interface of the device took over, and in this regard, Garmin’s Edge 510 was a pleasure to use. Every process from acquiring a GPS fix, customising fields, or viewing ride data was quickly and easily executed using a combination of the 510’s touch screen and buttons.
Quarq recommends zeroing the cranks before every ride. Just as anybody using a set of scales checks that they are reading zero before stepping onto them, so it goes for a power meter. The ELSA RS has a built-in Auto Zero function that is activated by spinning the cranks backwards five times then pausing for more than four seconds. The LED in the spider flashes as the power meter is zeroed — a matter of a few seconds — and then it is ready for use. This function can be performed while coasting on the bike, but is best performed before setting out on the ride.
Alternatively, and preferably, the cranks can be manually zeroed using the head unit before clipping into the pedals. I found myself incorporating this step into my start-up routine for the Edge 510 where all I needed was one or two minutes to ensure all sensors were up and running. Once the power meter is “calibrated” (the Edge 510 refers to this process as “calibration” rather than “zeroing”) a value is reported on the screen; values greater than 1000 suggest a malfunction. Over the course of the review period, my calibration values ranged between 20 and 90.
I have to admit to suffering a certain amount of data-induced blindness while using the ELSA RS cranks. After more than 25 years of road cycling, this was my first experience with a power meter and I had a lot of data at my disposal. I was fascinated by the power balance data and curious about the number (in watts) that described each of my efforts. I wasn’t oblivious to the world around me, but I wondered on occasion if the little screen on my handlebars wasn’t as distracting as a mobile phone in the hands of a driver.
The most important aspect of a power meter’s performance is consistency, such that a 250W effort made on one day is also measured as 250W on another, regardless of the interval in between. Unfortunately, the only way to judge this is with dedicated lab equipment over a range of loads, which is well beyond the scope of this review.
Quarq does not offer any software for viewing or analysing power data but there are already plenty of options available such as Golden Cheetah and TrainingPeaks. I took advantage of Garmin Connect to upload my ride data from the Edge 510.
In addition to reporting averages, Garmin also adds some metrics developed by TrainingPeaks such as normalised power, intensity factor, and training stress score to help with analysis. However a good handbook and/or an experienced coach are recommended to fully realise the value of a power meter for training and racing.
At around $1,900, the ELSA RS is an expensive product, but it is in line with other crank-based systems. There is a risk that some buyers will get frustrated as they contend with the cost of all the necessary extras. Similarly, the compatibility of the cranks for Shimano chainrings will attract riders using Shimano’s 11-speed groupsets only to frustrate them due to an incompatible bottom bracket axle.
Both issues are easy to forgive though, because the system is easy to install and simple to use while promising a high degree of accuracy.