Treadmill belts will stick for several reasons. They may be damaged, off-centre, need lubricant or the tension may be too tight or too loose. The sudden jarring movements that a sticking treadmill can produce may cause injury, so it's best to fix the problem. To fix a sticking treadmill belt, you must perform proper maintenance, which should eliminate the problem.
Turn your treadmill on, setting it at the lowest speed, and watch as it runs through several revolutions.
Look for cracks or tears. You will have to get a new belt if this is the problem. If there are no tears, it's possible that the belt needs to be lubricated.
Turn the power off and unplug your treadmill.
Loosen the belt by first finding the screws that hold it in place. These are usually located on the front and back of the walking deck. Turn the screws counter-clockwise to loosen them.
Lift the belt away from the deck and apply lubricant (purchased at any store that sells treadmills) to the deck. Be sure to read the instructions on the bottle before you do this. Your owner's manual will list the lubricants recommended by your treadmill's manufacturer.
Clean and lubricate the rollers while the belt is lifted. This process may vary depending on the manufacturer, so you should check the maintenance instructions in your owner's manual. Typically you can do this by turning the screws or bolts that secure the rollers to the deck to loosen them and, using a damp cloth, wipe the rollers, then apply lubricant.
Tighten the roller screws to secure them once more. Return the belt to the deck and tighten the screws. Turn the treadmill on again and let it run for at least five minutes set at low speed. If the belt is still sticking, the tension may need to be adjusted.
Check your owner's manual to find the adjustment screws that control your belt tension. These should be located on the front or back of the walking deck. When you find them, you can loosen the tension in the belt by turning the screws counter-clockwise. If the tension is too loose, turn the screws clockwise.
Find the screws that control your belt's alignment so that you can centre it. Typically they are located on the sides of your treadmill. To move the belt to the right, adjust the screw on the left. To move the belt to the left, adjust the screw on the right.
Run your treadmill for at least five minutes on its lowest speed. You may need to readjust the belt a bit more to get the appropriate tension and alignment.
According to Treadmill Sensei, a dirty treadmill will cause issues with the belt. After turning off the power, clean your treadmill at least once a week by dusting the belt and the space between with a damp cloth. Do not use cleaning solutions as that could make the belt slippery. Wipe the frame and console as well. Always follow the manufacturer's instructions regarding lubrication, which can be found in your user's manual. Frequently check the belt to make sure it isn't too tight or too loose and that it is aligned properly. A loose or off-centre belt will wear, which causes rips.