Your mountain bike has only two points where it touches the ground. That in itself makes your tire choice extremely important in how your bike pedals, corners and gets you over the slippery bits. Without the proper tire choice an excellent rider can be left in the dust (or mud) of a less-skilled, well tractioned rider. The basics of tire choice come to a few simple concepts: tread, width, pressure and diameter.

Tread pattern makes a huge difference in how a bike will handle on the trail. While an ultra-knobby tire may be good on the roots, without an open pattern it could very easily clog in the mud.

The three tread patterns shown above for instance will have very different handling features while riding. The far left is a Kenda Karma. This is an open disign that will shed mud easily but will not necessarely bite in as well as some tire as the knobs are short and evenly distributed. The middle tire on the other hand is a Kenda BBG. The open design will again allow for mud clearing while the perpendicular nature of the tread will bite in well under pedaling and braking situations. The disadvantage to a tire like this is that sliding on rocks and roots could be enfasized by the uniform nature of the centre tread. The tire on the far right is a Kenda Nevegal. This tire takes a different approach than the other two. Using well-spaced large knobs in a V-shape, this tire clears mud well while still offering good traction inder pedaling and braking. The agressivness of the tread will run a little slower than a lower profile tire but this is a great choice for wet and varied terrain.

When looking at a tire for winter use look for large knobs with lots of open space. The size of the knobs will improve traction while the open space will allow for mud to clear from the tire an not pack up. A V-Shaped tread pattern also helps with mud clearing and traction.

Another aspect of tire choice to take into consideration is width. The different between a thin and broad tire makes a huge difference in wet weather. The general rule of thumb is a wider tire will work better in wet conditions. This catch-all statement breeds out of a few factors. A wider tire has a higher volume so can be run at lower pressure than a narrow tire. This lower pressure leads to a greater surface area of the tire on the ground. The contact surface area of the tire is also larger due to the wider profile of the tire. By having a larger contact patch with the ground, one’s weight is better distributed over a larger area and thus receives better traction. The downside of course is that a wide tire has more rolling resistance and is inherently heavier than a narrow tire.

The last aspect of tire choice to consider is the actual diameter of your wheel. While this may not be as easy of a decision as simple width or tread when you are purchasing your next bike this is something to consider. The 26″ vs. 29″ debate has been running rampant for a few years and 650B (27.5″) even comes into the discussion from time to time. The size of your wheel directly effects how the bike rolls over obstacles, handles in corners and affects the overall ride characteristics of a bike.

For a full breakdown of the 29″ wheel philosophy check out this recent article on the benefits of the 29er. For the sake of this discussion though, the size of your wheel affects contact patch, momentum and acceleration. A 29″ wheel has a larger circumference than a 26″ and that translates much like riding a wider tire in that the surface area of the tire that touches the grand is larger. This improved contact patch allows for greater traction when riding in slippery conditions. This improved traction combined with the larger wheel’s rolling characteristics can make for an even better muddy-condition ride.