While using my Nordictrack a2550 this morning, the walking belt began to slip very badly. I checked the alignment and adjusted the tension of the belt as per the user's manual but the belt stills slip very badly. Please help.

Harvey, there are problems with the front plastic pully slipping on the metal drive roller. It appears that the drive belt is slipping. Just make sure that you rule the pully out first. If after that the pully stops with the front roller and the walk belt, there are only Two different drive belts used, double check the part number. Usually I use a ratcheting strap to pull the drive motor up to the bracket, because the belt is so tight there is no other way to get the motor close enough to the bracket to get the 3/8" bolts to even start into the motor. If you did not severly struggle to install the new drive belt, chances are its the wrong one.

Matt

If you need further help, I’m available over the phone at https://www.6ya.com/expert/matt_8dbc24bf722649ac

Do you know if you are tightening it correctly?
Both bolts at the back of the walking belt should be turned clockwise to tighten the belt. You must also tighten the bolts the same amount and typically no more than 1/2 turns at a time. I usually adjust belts while the machine is running at approx 3 mph. Your belt should be just tight enough to not slip when you walk on it. If its too tight you'll wear out the motor bearings.

Check page 27 in the owner's manual:

"If the walking belt slips when walked on, first remove

the key and UNPLUG THE POWER CORD. Using

the allen wrench, turn both rear roller bolts clockwise,

1/4 of a turn. When the walking belt is correctly tightened,

you should be able to lift each side of the walking

belt 3 to 4 inches off the walking platform. Be

careful to keep the walking belt centered. Plug in the

power cord, insert the key, and carefully walk on the

treadmill for a few minutes. Repeat until the walking
belt is properly tightened."

Tighten the rear roller bolts evenly with the unit off. The correct tension is when you firmly lift up on the right and left edges in the middle of the walking belt and get 2-3 inches gap above the walking board. If one side is looser than the other, the walking belt may wander sideways. Turn the rear roller screw on the side that it shifted to in a clockwise manner(1/2 turn at a time). Test on a low speed and adjust as needed. (you may manually recenter the walking belt with your foot if it shifted too far to one side and is rubbing on the plastic edges.) You likely have a worn motor belt that needs changing or even a pulley on the front roller that is slipping and needs replacing. They all cause slippage.

If the walking belt slips when walked on, first remove the key and UNPLUG THE POWER CORD. Using the hex key, turn both idler roller bolts clockwise, 1/4 of a turn. When the walking belt is correctly tightened, you should be able to lift each edge of the walking belt 2 to 3 in. (5 to 7 cm) off the walking platform. Be careful to keep the walking belt centered. Then, plug in the power cord, insert the key, and carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened.
If their is still slippage then the drive belt will need to be adjusted.
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. 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 but do not remove.

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 above. Tighten the bolt and test. If the problem is not corrected, if problem persist replace drive belt

If belt hesitates or slips when walking on unit it may be caused by either a loose walking belt or a loose drive belt. To determine the cause perform the following test: Stand beside Tread-Climber® fitness machine and set speed to 2 MPH. Step on one treadle and attempt to stop movement. If one belt stops but roller at rear and other belt continue to turn walking belt tension should be adjusted. If both belts stop but motor is still turning the drive belt tension should be adjusted.
Adjust walking belt tension at the front of the unit using the provided hex wrench on the exposed adjustment bolts located on each side of each front roller. Be sure to adjust both bolts on each roller the same amount as to not disrupt belt alignment. Tighten (turn clockwise) each adjustment bolt in full turn increments. After each adjustment, restart unit and check to see if belt slippage has been eliminated. Repeat if necessary.

It sounds as though you do not have enough tension on the running belt or the belt that drives the front roller from the motor is slipping. You need to identify which is the culprit and then adjust to get more tension.

Sounds like the BELT tensioner........

PROBLEM: The walking belt is off-center or slips when walked on SOLUTION: a. If the walking belt has shifted to the left, Start unit @ 1.0 mph using the hex key, turn the left idler roller bolt clockwise 1/2 of a turn to move belt to the right. Be careful not to overtighten the walking belt. If the walking belt has shifted to the right, turn the left idler roller bolt counterclockwise or clock wise 1/2 of a turn depends on the tension that will be on the belt take your time and walk on it to feel the belt underneath you Repeat until the walking belt is centered.

The walking belt may be too loose. If you have made recent adjustments, lubricated, or had repairs, a belt can slip if not tightened. The belt can slip if you have too much friction or if the belt has been recently lubricated. If lube does not help your problem and you have exhausted all other possibilities, the walking belt is most likely worn out and must be replaced.
To adjust the belt: Less Belt Tension: turn both adjustment bolts on back of treadmill in a counter-clockwise direction. More Belt Tension: Turn both adjustment bolts equally in a clockwise direction. Center Adjustment (moves belt center to the left): Turn left-side adjustment bolt counter-clockwise. Center Adjustment (moves belt center to the right): Turn the left-side adjustment bolt clockwise.
An over tightened walking belt can raise the amp draw of your treadmill, contribute to seam separation on the walking belt, or both, so do not over tighten the walking belt.
You should be able to lift the belt in the center on the side by approximately 2” to 3”, if you cannot lift it by 2” to 3”, the belt is too tight.