Mountain biking was originally the one phrase we needed when referring to riding a non-road bike on trails. However the word now has become a general umbrella term for a wide and growing variety of sub-categories, depending on the type of trail, the vertical change, the general speeds, whether it’s mostly up or down or equal, etc. At the speed-centric end of that spectrum is Cross-Country or XC riding – where the trails are generally more rolling, winding, less technical, with few if any drops, and the speeds are faster. Often this also includes long sustained climbs and long, fast descents with some technical sections, but mostly flowy terrain. For this terrain – and the racing that shares the name – XC bikes are the best option. This type of bike is also considered ideal for marathon riding/racing, which are typically XC-style routes of 50 or more miles.
XC/Marathon bikes are a fairly well-defined group with few variations in suspension and/or geometry: They usually feature 90-120mm of travel, with a large majority around 100mm; geometries are more aggressive than their more vertical-centric cousins, with steep head and seat tube angles providing a more upright position. Virtually all recent models have 29-inch wheels with a few at 27.5 inches, and at this price range most feature carbon frames (often with an alloy rear triangle). The combination results in ultralight, highly efficient bikes that offer super-quick acceleration, precise turning, and maintain momentum extremely well. The downside is mostly in descending – the forward position can feel twitchy in the front end, and can make these bikes prone to endos, and the shorter travel means harsher landings and overall ride feel. There are two main sub-categories – full suspension and hardtail (front suspension, but no rear), and a few other variations like full-rigid, fat bikes, and so on.
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