|Ultimately your tires only touch the ground over a couple square inches at most, but it is a rather important connection. Tires are specialized to work best on their respective type of terrain, so none do a great job in every condition.|
When picking a tire, first determine what kind of pressure you want it to have. Most road tires can be run at 110 psi or greater, while some tubeless mountain bike tires can be run as low as 20 psi.
On hardpacked conditions, the center ridge of your tire is very important. The closer it is to continuous, the less rolling resistance it will have. On softer terrain, having a wider tire with more knobs to propel you forward (almost like the prop on a paddle boat), is the way to go.
There are several different tire formats to consider as well, each with their own specific advantages and disadvantages, such as clinchers, tubulars, and tubeless tires.
Mountain Bike Tires Tubeless
Tubeless tires for mountain bikes
require a special rim
and are not compatible with normal clincher rims.
Typically, tubeless tires have stronger belts and armor in them than a normal clincher tire, so flats are fairly uncommon when compared to a typical clincher tire and tube.
Tubeless tires can be run at a much lower pressure than a clincher tire, allowing the rider to get more rubber against the ground, at the cost of increasing the rolling resistance of the tire. This is good for mud and sand, but not good for hard dirt trails.
However, normal clincher rims
can be made into a tubeless configuration with normal clincher tires if you use a tubeless conversion kit
such as Stan's Tubeless Solution.
Importance of The Center Ridge
A tire with a continuous center ridge greatly reduces rolling resistance, but decreases its ability to climb up uneven terrain (like wet rocks or roots) and its ability to propel the bike forward on loose terrain (like sand and mud).
Often tire manufactures will change the durometer of the rubber in the center ridge in relation to the outside of the tire. A denser, harder center ridge gives additional grip to hard surfaces, while softer side knobs give more grip for cornering and such.
Determining the correct center ridge a mountain bike
has is a fine science. If the terrain you ride on is hard packed, then you want something with a pretty continuous center ridge. If you use your mountain bike
for commuting, then you might consider one that is fully continuous. Likewise, if you find yourself riding on a lot of rocks, sand or mud, something that has less of a center ridge would be a better idea.
Road Bike Tires Tubular (sew up)
If you have a lot of money, this is a great place to spend it. A good pair of tubular tires are about as good as it gets performance wise, but they come at a substantial cost, so much so that they are not affordable for a typical recreational rider.
They get the nickname "sew ups" because the two edges of the tread carcasses are sewn together with the tube inside (so they have no beads).
Tubular tires usually weigh less than their clincher counterparts, but if you have to carry a spare, they end up being heavier than a pair of clincher tires with an extra tube and a patch kit. Of course, that extra weight isn't rotational weight (weight on the wheels
is amplified by the fact that you are working to move them constantly), so whether or not this is a benefit or disadvantage is debatable.
If you get a flat with a tubular tire, you're pretty much up a creek (unless you've got a sag
car waiting on you with an extra wheelset). Tubular tires need to be glued to their rims
and it takes the glue about 12 hours for that glue to harden properly.
In a partnership between Hutchinson and Shimano, there are now tubeless tires for cyclocross bikes. Now roadies can stop drooling over the cool tires that mountain bikers have been enjoying for some time and get a pair of their own.
General Terminology Clincher Tires
This is the most typical kind of tire in both mountain biking, and road biking. It simply refers to a tire that needs a tube, but is separate from that tube (unlike tubular sew up tires).
This is the body of the tire.
TPI stands for "Threads Per Inch." There is fabric woven through the carcass of a tire, and thinner tires have a higher TPI number. This is important because tires that are thin typically perform better than thick ones. They often have a lower rolling resistance and are more flexible.
This is simply the rubber on the tire that comes into contact with the ground.
Rolling resistance is the mechanical friction generated internally in a tire by having it bend and conform to the ground under it. The forward energy you put into the bike is converted to friction in the tire. There are two ways to decrease rolling resistance. You can use a tire with a higher pressure so it doesn't bend as much, or you can decrease the tire's resistance to being bent by making the walls thinner (or you can do a combination of both).