XC bikes generally are light bikes with short travel suspension meant to be snappy for acceleration as well as handling. Steeper head tube angles and shorter wheelbase that lead to the ability to change direction quickly.
- That “fast” handling is aimed at things like sharp cornering for stuff like switch backs and/or line selection on or around obstacles. These have a genesis of being “road race bikes for dirt” in many ways despite taking on more MTB specific features over the decades.
Trail bikes tend to me in the middle of the MTB spectrum (XC to DH) and are most often what people tend to have in mind with the overly generic term of “mountain bike” these days. Geometry that is slacker than XC race bikes and more suspension travel as well.
- These are often aimed to be the Swiss Army Knife type of bike that can do a bit of everything and not really suck at any of it. These bikes are more “stable” with the slacker head tube angle and longer wheelbase. They still handle reasonably quickly for cornering, but lose some of the “twitchy/nervous” nature that comes with XC bikes mentioned above.
- Without knowing exactly where someone rides or what they really want from a bike, this is one of the “safe” options to start with for people wanting a “mountain bike”.
Gravel bikes is really a separate thread here, but I understand why you are asking about them in this context and will cover them a bit. These tend to be drop style handle bar bikes (but more flat bars are emerging) with wider tire options than road or CX bikes. These have their own spectrum that runs from stuff like “race” bikes out to “touring” bikes which means large differences in geometry, suspension, tire and gearing options.
- Broadly speaking, “gravel” seems aimed at “roads” that are not paved or concrete, rather they are less maintained dirt roads that may have a wide range of rock (gravel) embedded or atop the dirt surface. The makeup of gravel roads varies WIDELY even within a single county, and gets wider when you look at different states and countries.
- Then consider that some people are pushing gravel bikes into “trails” that are most often associated with MTB and we get a bike that may well be a different version of a Swiss Army Knife in the bike world.
- I will either find a related article that covers the range or make a quick summary for this topic.
- A bit like differences in roads, MTB trails and such vary WIDELY between regions. Some have super narrow trails with trees, rocks and such that may dictate more narrow bars. But there are also regions with wide open ranges of trails where flopping the bike around is aided by wider bars (and associated shorter stem).
- There is no singular solution that is right for everyone. But with bars, it’s easier to cut wide ones down than make people upgrade to wider ones after the initial purchase. So that is the “better” starting point and people can cut them down as they see fit
- I have seen some guides on forks that can help with this and will link them in once I find them.