There are bolts at the rear of the treadmill on each side they are usually allen keyed . tighten each of them evenly so the belt runs true do this a little at a time and test belt by stepping hard on belt . if the belt stays and the drive rollers still moves tighten some more , if it pulls your foot along then you have good tension . note not to over tighten as this will cause damage to machine good luck
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There are bolts at the rear of the treadmill on each side they are usually allen keyed . tighten each of them evenly so the belt runs true do this a little at a time and test belt by stepping hard on belt . if the belt stays and the drive rollers still moves tighten some more , if it pulls your foot along then you have good tension . note not to over tighten as this will cause damage to machine good luck