Assuage with power.
Few brands in the power meter game combine function with price as well as Quarq, but—since the brand is part of the SRAM family—every new generation of Quarq tech means Shimano riders may be in danger of being left with less effective or more expensive options. The DFour Power Meter Crank Arms for GXP bottom brackets assuage those worries by bringing the latest Quarq power meter model to those of us who insist on Japanese drivetrains. The crank arms themselves are all SRAM; they're built with the same Exogram construction process used in the brand's top groupsets, so it saves around 200 claimed grams over the aluminum model.
The DFour is, essentially, the DZero model but with one fewer chainring bolts and a bolt circle diameter (BCD) that fits Shimano's latest generation of 11-speed road chainrings, specifically Dura-Ace 9000 (sorry, no 9100 compatibility yet), Ultegra 6800, and 105 5800. Except for that compatibility difference, the DFour incorporates every piece of technology Quarq crams into the DZero. Chief among these is the power meter itself, which saw a healthy amount of retooling. Overall, Quarq claims that "150 documented improvements" inform the evolution from the previous models to DFour, but the most important is to the heart of the meter itself: the strain gauges and measurement circuitry.
It still incorporates five strain gauges strategically placed throughout the spider in order to measure the Newton meters you're throwing into the pedals. It's also still got the same claimed accuracy of +/- 1.5%, so its numbers are 0.5% more accurate than most meters, but the new design requires less correction in order to maintain accuracy in drastic temperature changes. Fewer corrections mean the DFour also better rations battery life than Quarq's previous power meter models, though when the battery does go out, you can still change it without tools or having to ship the whole thing to the manufacturer.
As with the DZero model it's based on, the DFour system's accuracy is further boosted by the return of Quarq's 10k dynamic temperature compensation technology, which alleviates the need for constant, mid-race zeroings in variable conditions. Even if it's just coasting for a few seconds or toggling through your head unit to the proper option, it can still be the difference between winning and losing. It's also obnoxious as hell. The DFour is equipped with an auto-adjust schedule based on a constellation of around 10,000 data points that chart how the unit responds to temperatures ranging from zero to 130 degrees Fahrenheit. This lets the power meter figure out the atmospheric details for you with minimal drift, so you can focus on turning the crank, not babysitting it.
Power Balance and Omnical are two additional returning features that record total output and output for either leg individually (Power Balance) and let you swap rings without recalibrating or negatively impacting accuracy (Omnical). As with previous Quarq models, the DFour communicates to your head unit via ANT+ wireless, but Quarq also adds Bluetooth to this generation. Up till now, we've always tempered the obligatory head unit-compatibility statement by writing that your current computer is likely already compatible with the power meter; now, we can just state outright that it is compatible.
We recognize that there is value in cycling components that can stand up to the elements we often encounter throughout the course of a year of training, but Quarq demonstrates its penchant for being overly thorough by ensuring that the unit's internals can handle comically extreme conditions. The system is waterproof for 30 minutes while submerged under one meter of water, a feature that will come in handy on days you take your bike on the swim leg, too.
Since the DFour is effectively a catch-all for almost every bit of tech Quarq has thrown at the power meter problem over the past decade, it includes the AxCad accelerometer, which provides cadence information without any additional sensors or magnets. The DFour is also compatible with training software suites including Training Peaks WKO+, Training Peaks, Golden Cheetah, and Strava. Unlike previous versions, the DFour's Bluetooth compatibility lets it sync with the Qalvin BLE app to easily tune, tweak, and set zero offsets.
- Quarq's latest power meter tailored for Shimano 11-speed
- Redesigned strain gauge system is even more precise
- Provides power for each leg individually
- Exogram carbon fiber crank arms mean no loss in stiffness
- Broadcasts via ANT+ and Bluetooth protocols
- Requires less correction for better data and longer battery life
- Easily swaps between frames and chainrings
- Battery can be changed by home mechanics without tools