Along with giving you a wider selection and expert advice, bike shop personnel will help you get fitted to the right size bike. You can get the bike either too big or too small, which will cause your enjoyment to suffer. Follow the tips below, and you'll have the exact fit for your mountain bike.
Standover height
When you examine the fitting yourself, the first thing you want to establish is the inseam clearance, or the standover height. You want to have plenty of room between yourself and the top tube when you come to a stop. There should be around four to six inches of clearance from the top of your inseam to the top of the top tube.
Leg and feet position
There's a nifty formula for determining the leg position for riding a mountain bike. When riding a mountain bike, the terrain constantly changes, raising you off the seat constantly, sometimes just slightly, other times completely off.
Therefore, you'll need to sit your saddle slightly lower than you would on any other type of bike. Be sure you take this fairly lower seat height into effect when you factor the size of the frame.
Riding compartment
The next thing you'll want to check is the rider compartment layout (the distance between the saddle and the handlebars). Once the proper leg extension has been determined, be sure the handlebar is one to two inches lower than the height of the saddle. You should not have the handlebars higher than the seat, unless there is some type of upper body problem.
Dual suspension bikes
With suspension being at both ends, you'll like your weight more in the center of the bike so that your weight is distributed evenly between the front and rear suspension units, thus allowing the front and rear suspension to work as an unit.
This can be done quite simply by using either a higher or shorter stem to lift the hand height, which will in turn adjust the upper body up and the weight towards the rear. The increase in rise should be no more than two inches, then the decrease in reach shouldn't be any more than two inches.
Test ride
Once you have taken all of these steps into account, you need to take the bike out and test drive the bike. Make sure you put on a helmet, even if you are going to be testing for a brief period of time. Be sure that the tires are set to the right pressure, and the shop has adjusted the bike for you properly.
You should have a shop employee look at your body position and ride height while riding, to determine if any further adjustments need to be made. Ride the bike around for a bit to get used to its handling and new equipment. Start off slowly, then give the bike a bit of time to present its personality.
After a few minutes, you might notice that something isn't working correctly or just doesn't feel right in general. If this occurs, go back to the shop and have the problem corrected before you rule out the bike.
The more you ride bikes, the easier it will be to tell the difference in the ride types. Keep in mind, it may take months and even years to appreciate the way a bike handles. Talk to those who ride, and ask them if they ride the bikes they sell. This way, you'll learn more about the mountain bikes you love so much!