Mountain Bike Tires
There are a wide variety of tire options available for mountain bikes because there are many competitive companies in this market place. If you take a few basic concepts into consideration, it shouldn't be too difficult to choose the right tires for your mountain bike.
Your first consideration is the primary type of mountain biking you do or intend to do. If you will be riding on a wide variety of terrains, you may even want to consider getting more than one set of wheels so that you can easily match your tires to your terrain. On most bikes it only takes a few minutes to change the wheels.
For those who mainly ride on one type of terrain, a selection must be of the type of tires that are most suitable. In most cases, you will want to consider tire weight, as mountain biking tends to involve a lot of carrying the bike and riding the bike up hills.
Some mountain bike tires weigh more than a pound, so weight can be a pretty significant factor. A few ounces one way or the other can really make a difference after several miles of riding. This can be particularly important if you are just mountain biking as a hobby and aren't on a professional conditioning program. It can also be very important for those who are into mountain bike racing.
Tires beaded with Kevlar tend to weight 60 grams less than the other tires on the market. The great thing about Kevlar is that it is very durable. The bad thing is that it costs more. But the price difference of around $5 per tire is a small price to pay for an easier ride.
Beyond tire weight, the type of traction you'll need is a factor. But traction can be a double edged sword. When you are peddling it gives you better grip so that you can accelerate faster and maintain better control of the bike. But when you are trying to conserve energy and coast, or when you are at peak speed, the extra traction increases tire friction, slowing you down slightly. But, the extra traction comes with some extra tire weight. So the best bet is to have better traction on slick terrain and less traction on rough, solid terrain.
The width of the tire is pretty much the same idea as the traction. The more you have, the easier it will be to maintain smooth contact with the road and the more it will slow you down. The less you have, the faster you'll be able to go on smooth terrain, but the less control you'll have over your bike. When terrain is rough, wider tires will generally do better.
As general guidelines, go for a rough tire on rocky roads. Knobby tires are really good, if the knobs are stiff. If you're overweight, start with a wide tire for stability, unless the terrain is particularly muddy. In muddy weather, your weight will help the thinner tires sink down to more solid ground.