My treadmill belt is sliding from left to right

Fit new belt ,check for slide adjuster slots.

You have not properly aligned and / or adjusted the tension. If it is SLIDING then you do not have enough Rear Tension. Once you get the right amount of REAR TENSION, then you have to adjust the left right (balance the belt). Your belt should go straight, right now you have it too far to the FRAYED SIDE. Turn the Machine on, have your Hex Wrench in the Bolt and turn it slowly CW and as the belt come back to Center, watch the adjustment. If it continues to go past, then loosen it a little until you have the right balance. Remember REAR TENSION FIRST... THEN BALANCE for Alignment

On both ends of one of the rollers are adjustment or takeup screws. You may need a screwdriver or open end or allen wrench to adjust them. If the belt is moving toward the right, adjust the right side of the rollers to be farther apart (if I'm not mistaken). This should cause the belt to walk to the left. Run the machine and watch for belt movement. If the belt is tightening too much, adjust the left side to make the rollers closer together. These adjustments are best made while the belt is running, but BE CAREFUL!
Gary

Find the allen key that came with the machine. If you don't have it, you will need a 3/16" allen key to adjust the roller.
If the belt is pulling to the right, adjust the right screw by turning it clockwise 1/4 turn with the belt moving. You may need to do this more than once. Between adjustments, watch the belt closely to see how much it moves to the left.
Unless something dramatic has happened to the frame or some other part, the amount of adjustment should not be too great..

Here is a basic procedure that will work for the majority of treadmills out in the market:
If the walking belt has shifted to the left, first remove the key and UNPLUG THE POWER CORD. Using the allen wrench, turn the left rear roller adjustment bolt clockwise, and the right bolt counterclockwise, 1/4 of a turn each. Be careful not to overtighten the walking belt. Plug in the power cord, insert the key and run the treadmill for a few minutes. Repeat until the walking belt is centred. b. If the walking belt has shifted to the right, first remove the key and UNPLUG THE POWER CORD. Using the allen wrench, turn the left rear roller adjustment bolt counterclockwise, and the right bolt clockwise, 1/4 of a turn each. Be careful not to overtighten the walking belt. Plug in the power cord, insert the key and run the treadmill

PROBLEM: The walking belt is off-center or slips when walked on SOLUTION: a. If the walking belt has shifted to the left, first remove the key and UNPLUG THE POWER CORD. Using the hex key, turn the left idler roller bolt clockwise 1/2 of a turn. Be careful not to overtighten the walking belt. If the walking belt has shifted to the right, turn the left idler roller bolt counterclockwise 1/2 of a turn. Then, plug in the power cord, insert the key, and run the treadmill for a few minutes. Repeat until the walking belt is centered.

please look under the bottom of the treadmill and be sure that your alignment brackets are not benmt/missing. (put the machine in the storage position and look about 2/3 way down the side of the belt) you should see a metal bracket on each side pressing in on the belt. They should be pressing in about 1 1/2 -2 inches to help track the belt.

if this is a resident unit. check the back of the unit. make sure there are no broken plastic pieces. if so this could be why you can not adjust the guide. if there is no broken pieces use the right screw to adjust guide. left to make belt go right and right to make belt go left.

Make sure treadmill is running when you adjust belt. The treadmill belt tracks as the belt goes around. I usually put machine on 2-2.5 if belt is not rubbing instantly. If belt is already against plastic, turn adj. counterclockwise on the opposite side about one full turn. You can usually move belt with your foot to see if it aligns any with turning on the treadmill. Once belt is not rubbing, turn treadmill on and continue alighing the belt.

The rollers in the front and rear need to be adjusted. If its sliding to the left, than the left side needs to be adjusted out until the belt stops going that way and stays on straight.