How to adjust a treadmill drive belt
The motor drive belt is adjusted independently from the walking belt. Some newer models have an auto tensioner which is a lever that has a wheel that puts pressure on the drive belt and a spring on the other end that automatically loads the belt to the proper tension. You should not adjust these since they are preset.
Tension can be affected slightly by adjusting the tension of the walking belt but if you have a slipping problem, the drive belt will require replacement. If your drive belt is too loose, it will slip on the front roller pulley or the motor pulley. If it is too tight, it will increase your amp draw to the point that you may have an electronics or motor problem. Due to this, it is better to be on the safe side and replace a drive belt rather than risk over tightening it. A drive belt is usually $29.99 or less while many parts you can damage by over tightening can be more than $300. Additionally, too much tension can cause bearing failure in the motor and the front roller and front roller pulley failure. It is better to err on having the belt a little too tight rather than too loose due to the possibility of injury if the belt slips.
Motor Belt Adjustment- Icon Units
Do not remove any of the mounting bolts to the motorthese repairs will require 2 9/16" wrenches and may require two people to accomplish the repairs
Before beginning this repair: Check to make certain that the drive belt requires adjustment. Check out belt slipping instructions or with the motor cover removed, walk on the belt normally and try to stall the belt to make it slip. Be careful during this test. If the problem is in the drive belt, either the drive belt will stop when stalled or the front roller will stop when stalled. If the motor, drive belt, and front roller continue to turn when the walking belt is stalled, the problem is with the walking belt slipping on the front roller. If the drive belt continues to turn but the front roller stalls, you may have a broken front roller pulley.
Find the motor mounts. Many motors in Icon treadmills have a main pivot joint in which a bolt runs the full length of the motor mount. This bolt will require loosening to provide maximum adjustability. Some models have a single jack bolt and others have an auto tensioner. Single jack bolts are the easiest to adjust.
Find the set bolt(s) on the motor. This is typically run through only one side of the motor mount or may be on both sides but it does not run the full length of the mounting. Loosen this bolt(s) but do not remove. Jack bolt models will have flat mounts and may contain up to four bolts.
Look for a bolt that will tension the motor. If it has this bolt, it typically runs in the same direction parallel with the drive and walking belts. If your treadmill is not equipped with this bolt, skip to Step 4. If your treadmill is equipped with this bolt (very few are) the repair will only require one person. Using 2 7/16" wrenches, make a few turns to this bolt, tighten the bolts from Steps 1 and 2 and test your treadmill for slipping. If belt continues to slip, repeat Steps 1, 2, & 3. If a second attempt does not repair the problem, skip to Step 5.
If your treadmill is not equipped with a bolt as described in Step 3, the drive belt must be tensioned by hand. While one person applied increased tension to the drive belt, the other person should tighten the motor set bolt(s) that are described in Step 2. Tighten the bolt from Step 1 and test. If the problem is not corrected, repeat Steps 1, 2, & 4 and retest. If problem persists, skip to Step 5.