When looking for mountain biking shoes, comfort and efficiency are the two most important criteria to consider. With their solid uppers, fiberglass reinforced soles, and inimitable Dynalast design, the Shimano SH XC31 Mountain Bike Shoes meet them both. The XC31s' knack for smoothing the trail is appreciated, but the shoes' real star is their inclusion of Shimano's Dynalast technology at such a forgiving price point. Dynalast increases your pedal efficiency by a claimed . 56%. While that doesn't seem like much at first blush, any cyclist who's ridden for longer than two hours understands the importance of marginal gains like this. They can be the difference between finishing a group ride or race at the front or struggling to hang on. Dynalast involves lowering the toe spring and heel section of the last while keeping the arch and metatarsal areas at the same height. This creates an optimal pedaling angle for leading into and exiting the up swing of your pedal stroke, so the dead spot is shortened and your efficiency is increased with each turn of the crank. The polyamide outsole is reinforced with fiberglass threads to strike a balance between stiffness and the amount of vibration that it transfers to your feet. After all, energy transference is a two way street, so while the XC31s aren't ideal for a one hour hammerfest race, they will keep you comfortable in the saddle for half day adventures. It's mated to a synthetic leather upper that beats its natural counterpart in every aspect where it counts. The synthetic is less stretchy, more durable, and lighter, so the XC31s' ability to resist deformation and shrug off grasping twigs and the occasional chance encounter with a rock or trunk doesn't come at the expense of weight.