The Modern off-Road Tire Explained

…You gottta have them

Buying new tires for your bike used to be easy. Once upon a time you looked at the wasted, chunked, bald “knobby” on your rim, wrote down the numbers on the sidewall and went to the parts counter at your local dealer for the same one that came with the bike when you bought it. You can still buy tires this way but you will most likely be doing yourself a disservice. Those tires that came on your bike have been chosen by the manufacturer in an effort to find a middle ground, a tire to work for all occasions, much like the suspension.

These days tire manufactures are making tires to fit very specific conditions. Whether you ride in sand dunes or hard pack clay, the right tire is available to you. For instance the knob dimensions for a hard terrain tire are very different from those of a soft terrain tire. The tire designed for hard packed conditions will generally have shorter knob depth and be more supported around its base due to the extreme flex/heat caused by the hard ground condition it encounters. Tires designed with soft terrain in mind will have taller, sharper knobs designed to penetrate the dirt for traction. An intermediate tread pattern is designed to have the best of both worlds.

The modern off-road tire starts its life in much the same way a tire did when Roger DeCoster first landed on our shores so many years ago. Almost all MX tires are made from Synthetic compounds. There have been many changes in materials but overall the manufacturing is pretty much the same. Off-road tires are made from a mixture of natural and synthetic rubber, natural rubber is used because it provides durability. Only a few desert tires use all natural rubber compounds. This is done to provide endurance against the high speeds. The biggest change in tire technology has been in rubber compound and overall tire weight. Weight is a very important factor as it is rotating mass and is unsprung. Tire development, as you can imagine is leaning toward building better performance on four strokes as they are much heavier and put the power to the ground differently.

With so many sources for tires your choices can be unnerving. All the different numbers on the side wall don’t seem to make sense. Then you start looking at the tread pattern and to make matters worse there is the pricing to consider, because you still want to buy a burger on the way home from your favorite track. One thing is certain in this process, new tires will do wonders for your riding and confidence. If you want faster lap times or just want to get to the top of that hill easier, fresh meat on your wheels is a far better investment than that pipe.

Let’s start with sizing. On the side of your tire there will be a series of numbers. Something like 80/100-21 would be a typical front for a full sized dirt bike. The 80 indicates the section width (side to side) of the tire in millimeters. The 100 indicates the width of the tire as a percent, so 100% of 80 would give you a tire width of 80 mm for a relatively equal height/ width in this example. The 21 indicates the size of the rim the tire will fit onto, in this case a 21 inch. A wider tire will give you more stability and grip but will be heavier and may feel sluggish. A narrow tire will turn faster and spin more easily but might not provide the traction you want. One thing many riders neglect is tire pressure, in order to achieve the best performance in any conditions you need to start by setting your tire pressures before each outing.

A good starting point for MX tires in dry terrain is 13-15 psi for the front and 10-13 psi for the rear. For softer terrain try a lower inflation pressure of 10-12 psi front and 8-10 psi rear. This will allow the casing to flex a little more providing better traction and help the tread to clean it self out. Tire pressure is extremely important, two psi can make a huge difference! Experiment with different pressures when you get new tires or ride a new track or trail. Make notes and keep them handy for the next time you ride the same place. This way you can find the optimum pressure and use it each time. You will be glad you did.

Leave a Reply

Your email address will not be published.