While the key feature of the GS Amp 3550 Carbon Clincher Wheelset is inarguably its PowerTap GS rear hub, the added stability of the mixed depth rims deserves special mention. We love the effortless way that 50mm rims maintain speeds around 23mph, but 50mm up front can make for trying times in the wind. This is especially true if, like us, you tend to futz around unnecessarily with head units, water bottles, and anything you happen to have in your pockets on a given ride all of which activities require hands free riding, which is dangerous when the front wheel is a side wind grabbing sail. By popping a 35mm rim in the front, PowerTap and Amp reduce the handling issues associated with deep rims while still taking advantage of aerodynamics in the rear wheel, where the power is produced. Handling aside for now, the power you do produce on these wheels is measured by eight strain gauges with a claimed 1. 5% accuracy rating numbers that to support PowerTap's role as the industry standard. As you send watts down to the pedals, the GS sends these numbers up to the head unit via the ubiquitous ANT, so chances are good that your current head unit is already compatible with the hub. Changing the battery, updating firmware, or servicing the meter can all be effected in minutes with the use of PowerTap's handy little tool, making this one of the most home mechanic friendly power meters on the market. The hubs are laced to rims built by Amp, a small manufacturer based in England whose focus is more on value and speed than name recognition. This focus manifests in both the PowerTap branding on the rims and as cost savings in the four digit range when compared with GS equipped carbon hoops from manufacturers whose decals add a premium to the cost. The wheels are anything but bargain bin, though. In addition to the mixed set's added stability, the rims feature the same slightly rounded spoke face that's become so common across the industry for its ability to temper ...