Does it feel like the belt is slipping under your feet when you walk or run on your treadmill? It may very well be, but which belt is slipping? That is the question.
I had a service call where a customer had what he thought was a loose treadbelt because they got a “slipping”, “stalling”, or “catching” sensation during use.
Assuming that the treadbelt was too loose, they attempted to remedy the situation by tightening the treadbelt. Each time they tightened it the slipping still continued.
They ended up tightening it so much that the adjustment bolts on the rear roller actually bent the steel frame tabs on the rear of the treadmill and you could not get a single finger under the treadbelt because it was so tight. However, it was still slipping during use.
The problem was not the treadbelt, it was the drive belt, also called the “motor belt” that was loose. The drive belt is the small belt that rides on two pulleys. One on the drive motor and one on the front roller. The drive belt on this particular treadmill was stretched out and needed to be replaced.
In another customer’s situation the treadbelt also appeared to be slipping and it would actually stop when body weight was applied during attempted use.
There were a total of three things that caused the issue in this instance:
1.) The deck and treadbelt were over lubricated.
2.) The treadblt was worn out so the smooth underside of worn out treadbelt pushed all of the silicone oil out to the sides during use.
3.) The edges of the treadbelt threw the silicone oil all over the drive belt as it rotated past it. This caused the drive belt to slip on the pulleys on the motor and front roller.
In this case the front roller and drive belt needed to be removed and thoroughly cleaned to remove all of the silicone oil from the drive belt as well as the pulleys. This was not an easy task. The worn out treadbelt and the badly worn deck also needed to be replaced.
If you are having this treadbelt “slipping” or “stalling” problem, you need to determine which belt is doing the slipping.
To do so, start by removing the motor cover being very careful not to touch any electronics inside. To do this there may be three screws on the front and one or two on the sides.
Sometimes on older treadmills there are two or three more screws on the underside of the treadmill holding the back end of the motor cover on. To get to these you need to fold up the treadmill and with the treadmill in the folded position, lay the whole treadmill back onto the floor towards where the deck was. These screws can be very recessed so you may need a long #2 Phillips screwdriver. Once removed you need to stand the treadmill back up again and unfold the treadmill.
Now with the motor cover removed, start the treadmill setting the speed to 2 MPH. Now try to use the treadmill and we’ll see what is slipping
Scenario #1
If the front roller stops but the drive motor keeps turning then it is most likely the drive belt that is slipping and is too loose.
There are a couple potential ways to remedy this. If the there isn’t an adjustment to loosen the drive motor and move it back away from the treadbelt and deck to tighten the drive belt, then the drive belt may need to be replaced.
NOTE: On some much older treadmills there may be a spring attached to a third floating pulley assembly midway that appies tension to the drive belt . On some other older models there there may be an assembly allowing the bolts to be loosened and the motor rotated back to apply tension much like the alternator on a car.
When properly tensioned you should only be able to twist the drive belt ¼ turn or 90º at the most. If more than that it may be to loose. If it is less then than ⅛ or 45º it may be too tight.
Scenario #2
If the front roller stops but the drive belt and pulley on the drive roller keeps turning then it may be that the pulley on the drive roller may have become separated from the drive roller and you will need to replace the drive roller.
Most roller pulleys are plastic and are pressed onto the roller which has splines in that part of the roller to grip the pulley. Sometimes the plastic pulley on the roller gives way from the splines on the roller and will no longer grip the roller.
Scenario #3
If the treadbelt stops but the drive (front) roller keeps turning, then it is the treadbelt that is too loose.
Tighten the adjustment bolts on the rear roller equally on both sides. Tighten them about ¼ to ½ turn to the right at a time.
NOTE: These bolts are also the centering adjustment for the treadbelt. If one side or the other is tightened or loosened too much then the treadbelt can go over to one side or the other too far. When this happens the treadbelt can become damaged or even fold over onto itself and damage the belt requiring replacement.
Test in between by running the treadmill at about 2 MPH and stomping down on the treadbelt to see if you can make it slip.
Be careful not to over tighten the treadbelt. This can put stress on the roller and motor bearings as well as the belts, causing premature failure.
As a rule of thumb you should be able to deflect the treadbelt about 2 inches off the deck by reaching in underneath the treadbelt, palm up at the midway point.
