One of my favorite moments in bicycling comes when you find the exact right combination of effort, gearing, wind speed, road surface, and slope. For a few magic moments, acceleration feels effortless, and you rocket forward like there’s a giant hand pushing you from behind.

Last week, I experienced something similar, but it came while riding uphill on the toughest section of Central Park’s loop road. The effortless acceleration was courtesy of a compact but powerful electric motor embedded in the frame of a new line of bikes introduced by Trek. The test ride was meant to introduce me to Trek’s new models, but it also introduced me to pedal-assist bikes more generally.

The experience was very different from my expectations, in part because there are multiple experiences, depending on exactly how you tweak a combination of settings, gearing, and effort. The results were anything from a gentle boost as I pedaled on the flats to ripping up a hill at speeds that made me a hazard to my fellow cyclists.