by Boxer Wyze

Created on: August 07, 2009

Figuring out exactly what air pressure you need in your mountain bike tires is not difficult. I've heard a lot of complicated formulas spouted by so-called experts about how to figure it out weight, terrain, skill level, climate, etc., but as someone who's been riding trails for many years all over the world I can break it down for you pretty simply. The two factors that really matter are traction and support. Once you have a basic understanding of these two things you will be rolling along nicely in no time at all.

When I talk about traction it simply means are your tires are getting a good grip on the trail surface. You don't want to waste energy spinning your tires and going nowhere. The main reason for spinning out as it relates to tire pressure is having too much air. When the tire is pumped up too much it can bounce around like an over-inflated basketball causing it to lose contact with the ground. Also, if you hit small rocks or other hard objects an over-inflated tire will slide off and again cause you to lose contact with the trail. Letting some of the air out will allow the tire to mold itself to the surface of the trail and create more surface contact. However, if you let too much air out you can create a different kind of problem. That's what I mean by support.

One of the most common types of flat tires in mountain bikes is what is known as a pinch flat. This is when the tire hits a hard object and forces the inner tube against the metal rim of the wheel and punctures it. This often happens when a tire is under-inflated and particularly in terrain that has sharp rocks or tree roots. The easiest way to avoid this problem is to make sure you inflate your tires to a pressure that supports your weight properly for the type of terrain you are riding.

So, too much air will give you bad traction and too little air will not support your weight enough to prevent flats. How do you balance it out? Easy; if you are an average rider between 130- 200 pounds you can set a starting tire pressure of between 40-45 pounds per square inch, or PSI. This will work pretty well for most riders and on most surfaces. If you are not a professional rider and just want to enjoy the weekend ride without too much trouble or worry this will give you a good starting point.

Once you start riding you can tweak it to get better performance. If you find your tires loosing traction all the time you probably need to let a little air out. If you feel that every rock and stick is causing your tires to mash against the wheel rim then add some air. Various conditions like muddy, sandy or rocky trails might cause you to adjust the tire pressure as well but the main thing to keep in mind is that easy balance between traction and support. Getting it right will be the difference between a smooth, flat-free ride and a jarring puncture-filled nightmare.

Now, let's ride!

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