When looking into a treadmill there are many things to consider.

Bed and Belt - The #1 problem with any treadmill is the friction that builds up between the running belt and the surface underneath (bed). This friction is what leads to almost every problem you could have with a treadmill over the course of its life. It is very important to find a treadmill that has a low coefficient of drag between the bed and belt. You should look for a treadmill that has a phenolic wax coating imbedded in the deck. The belt should be a 4-ply belt that uses a high-density polyester weave on the underside of the belt to provide low friction and less wear. Stay away from special padded belts that are supposed to provide shock absorption as they wear out much faster and provide little shock absorption.

Motor - The first thing to do when comparing motors is make sure the motor is rated in continuous duty horsepower (hp). Some manufacturers rate peak hp, which is the point at which the motor will fail. This is misleading because this is the maximum the treadmill can produce before failing. Some people will tell you that hp is not important because you will never use more than a small percentage of the total hp. Or they will say that the most hp you can use on 120V/15 amp home circuit is 2.47hp. This is true, however a larger motor will last longer because it will run cooler because you will be using a smaller percentage of motor. Another important factor to consider is that a larger motor will feel smoother compared to a smaller motor. With a more powerful motor you will not feel any of the hesitation that is normally associated with the smaller motors.

Shock Absorption - This is important not for the life of the treadmill, but for your personal well being. Obviously, you don't want to be running on a hard surface as this is not good for your joints. But you also have to make sure that the surface does not have any lateral movement. Try to get a treadmill that has a floating deck. A floating deck is one that is not bolted to the frame of the unit. This means that the deck is separate from the frame. But not all floating decks are created equal, the deck should not move side-to-side or back and forth. It should have a system in place to absorb shock while keeping lateral movement to a minimum.

Stability - The amount of stability required is going be different for many people. Don't be offended if a salesperson asks you over the phone about your height and weight. This is to determine which unit is going to fit your needs. A larger person will have a very hard time feeling comfortable on some the smaller treadmills on the market today.

Longevity - There are many factors to consider when determining how long a treadmill is going to last. Once again motor size is important in terms of longevity. But you must also consider other factors, such as the diameter of the rollers. A larger diameter roller will not spin as much; therefore increasing it's useful life*. You should also try to purchase a treadmill that has a reversible deck. This means that when it comes time to replace the bed and belt, all that you will have to do is buy a new belt. The deck is then flipped so that you can use the other side, which is still brand new. This will save you about $300- $400 on the cost of a new deck. Also it important to purchase a treadmill that is heavy in weight. A heavier treadmill will not only be more stable but it will last longer as well. A lighter unit will rattle around a lot more as you walk and run. This can lead to premature failure in the rollers, motor and electrical components.