Mountain biking in muddy or wet conditions can be a serious thrill. You'll almost certainly get muddy, but with the right tires you'll improve your chances to avoid injury. The dangers of losing traction and eating dirt are exacerbated when the rain loosens the top layer of soil on the trail. Leaving for your next ride with the right pair of mountain bike tires can be crucial for keeping your traction on a saturated trail, where performance and grip are of paramount importance.
Mountain Bike Tire Function
When mountain biking on a dirt path, the tire functions in a very different way than that of a road bike on pavement. The rubber knobs on a mountain bike's tread, often referred to as teeth, provide grip on loose, unconsolidated material by digging in like small spikes. On many sets of bicycle tires, these knobs are set up differently between the front and back wheel. On the front they're arranged parallel with the direction of travel for steering and control, while the back tire's knobs are arranged perpendicularly to provide stopping power and traction.
In the 1980s a bicycle company called Specialized revolutionized tread design for mountain bikes with a new kind of knob placement. By using taller, reinforced knobs on the outside edges of the tires, they created a pinching effect while banking, since the reinforced knobs couldn't bend outward. As the tire flattened out on a particularly intense drive, these knobs bent inward, providing a much better grip. This design cue is replicated in most modern mountain bike tires and provides superior grip in wet conditions.
Proper Tire Pressure
Since most modern mountain bike tires have the knob configuration that is most effective for wet weather riding, checking for proper tire pressure becomes the next most important thing you can do to improve performance. A properly inflated mountain bike tire deforms when under the weight of the bicycle and rider, but cannot deform enough to allow the inner tube to be completely pinched between the outer tire and the rim. Check to make sure your tire bulges out slightly on either side of the contact point between the tire and the ground. Adjust the pressure as you ride to optimize the level of deformation. A stiffer, overinflated tire will perform poorly in wet conditions since it has less contact with the ground.
The rubber that coats the fabric of the tire can vary between manufacturers and prices. Generally, paying more for a tire provides a higher quality tread that will last longer. In the case of wet weather performance, the best type of tread is softer, specifically molded for stickiness in wet conditions. This softer tread will wear faster than stiffer treads, but the added grip from a more easily deformed tire will result in an overall gain in traction. The stickiness of the rubber is not as important as the tread configuration and pressure of the tire, but can give you an additional boost when your ride takes you onto slippery trails.
Max Roman Dilthey is a science, health and culture writer currently pursuing a master's of sustainability science. Based in Massachusetts, he blogs about cycling at MaxTheCyclist.com.