SRAM Quarq has a decade of powermeter engineering and design in the bank, across many models and options. Some of the Quarq-only features impress and attract Shimano riders as well. The SRAM Quarq DFour Power Meter Chassis was designed for cyclists who want to run a Quarq with their 1st generation (9000, 6800, 5800) drivetrain. You get the crankarms, spider/powermeter, and axle, just needing to supply your Shimano proprietary 4-arm 110 BCD chainrings. With the DFour, SRAM surpasses the Elsa RS. The Bluetooth low energy (BLE) technology and ANT+ wireless data transfer choices delivers more options and simple smartphone direct set-up. The new Qalvin BLE app powered wireless firmware updates, diagnostics, power meter zeroing and calibration, and is equally useful for home or bike shop service, and riders of any level. You can even change the power meter’s slope using the built-in calibration routines. It is great to have such a simple and useful interface for these processes.

The powermeter itself is housed in a CNC machined aluminum spider that is mated to a lightweight Exogram™ Hollow Carbon crank arm with the stepped 22/24mm GXP or BB30 spindles. The combination was developed for complete integration. The stiffness and power transfer of the crankset is excellent, and there is zero power loss from the spider design. Your Shimano 9000, 6800, or 5800 chainrings will bolt right on the spider via the Shimano hardware (the DFour91 has been released for R9100/R8000 chainring users). The OmniCal calibration system ensures that you can install and change rings without impacting the power meter's overall calibration. The alignment of the four arm design keeps the Quarq battery compartment completely accessible on the front of the crankset, just above the arm. ANT+ or BLE transmission is verified by LED for simple, clear operation, and Quarq makes the ANT+ ID visible to ensure proper connection.

Quarq has installed their AxCad™ accelerometer, which eliminates the need for a cadence magnet. Given the shape and size of the spider, many frames formerly had difficulty accommodating the unit and the magnet. Now the set-up is cleaner and you have more frame clearance. AxCad is a highly reliable measure of cadence while pedaling, and reacts quickly to changes and stoppage. Many power meter manufacturers have struggled to address temperature variation, but the engineers developed new sensors and firmware, called 10K™ temperature compensation, that eliminates temperature effects on power measurement through more frequent, more accurate temperature readings throughout the pedal stroke. Quarq considers the DFour to be accurate in all conditions to within +/- 1.5%, placing it among the most accurate power meters on the market.

ANT+ wireless transmission gives you maximum flexibility in your choice of head units from Garmin, Lezyne, and so on. Or you can choose BLE capable units or smartphones. Syncing your DFour is simple, as is your pre-ride zeroing. All of the usual power measurement metrics are measured and calculated for your head unit and can be downloaded or transferred to your favorite training and analysis programs, such as Training Peaks, Strava, and Golden Cheetah. The widely available CR2032 battery generally delivers 300 hours of transmission before replacement is necessary, so you won't have to worry about losing data. Quarq power meters have an IPX7 waterproof rating, so you ride in the rain all you want. They feature a 2-year warranty, free firmware updates, and strong Quarq-direct support.

The bottom line is that if you have a frame with the GXP bottom bracket standard option, and want to run a Quarq powermeter with the 1st generation Shimano 11-speed double drivetrain, the DFour Power Meter Chassis was designed just for you. You make no sacrifices in shifting quality or performance and get one of the most accurate power meters available. The 580-620 gram crank weight is competitively light and stiff, so again, no sacrifices.