Treadmill Belt Is Slipping – 5 Possible Causes


Treadmills are invaluable pieces of equipment for many runners. They’re handy for running at unusual hours, when the weather is bad, or when you just don’t feel like leaving the house to get our miles in.

But like any piece of machinery, they can sometimes stop working as effectively as they’re meant to.

Sometimes all your treadmill needs is some lubrication, but other times the problem is larger.

Maintaining and caring for your treadmill isn’t hard if you check it regularly and keep on top of issues.

One common problem that occurs is the treadmill belt slipping to one side when you’re running. This can be a strange and scary feeling.

We’ll cover possible causes and fixes in this article…

Treadmill Belt Slipping

A slipping treadmill belt is one of the most common problems that treadmill owners encounter.

If you’re running on the treadmill and suddenly feel the belt moving to one side under your feet, that’s slipping. The belt is meant to stay in the same position, in the middle of the deck. There shouldn’t be side-to-side movement.

Slipping can be dangerous. Think of the classic falling scenario – slipping on a banana peel. Simply standing on the banana peel isn’t what causes the fall. The fall occurs when the banana peel moves suddenly and at a completely different angle to the way the person is moving.

The same is true for a slipping treadmill belt. When you’re running in one direction, even a slight shift in the surface below you can throw you off balance and lead to a fall.

A fall from a moving treadmill is extremely dangerous, as the treadmill will keep moving for a short amount of time (even if you’re using the safety tether).

When you land on the road, it’s a stationary thing. Landing on a moving surface can increase the potential for injury.

Is It a DIY Fix?

There are steps that you can take by yourself to fix the issue of the treadmill belt slipping. Sometimes, these steps will be all that’s needed to secure the belt and prevent it from happening again.

If you do attempt to fix the belt and it doesn’t work, you may need to call in a professional to help you. It’s better to spend a little extra than risk damaging the treadmill.

Remember, if you attempt repairs on your treadmill while it’s still under warranty, you will void the warranty.

5 Reasons a Treadmill Belt is Slipping

If your treadmill belt is slipping, the most important thing is to figure out the reason behind it. If you can work out why it’s happening, it’s far easier to fix it.

Here are the 5 most common reasons for a treadmill belt to slip:

1. Belt Is Too Loose

If the belt isn’t tightened enough, it can slip to one side while running on account of the extra length.

It’s easy to test and see if this is the reason for your treadmill belt slipping. With the treadmill off, slide your hand under the belt and lift it up. If it lifts more than 2 to 3 inches, then it’s too loose and needs to be tightened.

Be sure to follow the instructions very carefully when tightening the belt. Tighten it little by little to avoid over-tightening. When you can slide your hand underneath it and it lifts about 2 inches, then it’s about the right tightness.

Make sure not to tighten it too much. If the belt is too tight, the treadmill has to work extra hard to get it moving. It could end up putting a strain on the motor, damaging it, and preventing the treadmill from operating quietly.

It also means the belt will most likely wear out more quickly, as there’s more friction between it and the deck below it.

If you are tightening the belt on your own, remember to align it back in the center before making your adjustments.

2. Missing Lubrication

Even the least expensive treadmills require a well-lubricated running deck in order to work most efficiently. If the deck isn’t lubricated, it can lead to problems like slipping and sticking.

Friction between the treadmill belt, deck, and rollers can cause them to wear out much faster than usual. It’s also dangerous because sticking, as well as slipping, can lead to missed steps and falling.

To reduce that friction, you need to lubricate your treadmill belt regularly. Consult your user manual to get an idea of how often you’ll need to lubricate it, as it varies by brand and model.

Also check which lubrication is recommended. Try not to use anything different, as you run the risk of damaging the treadmill. A silicone-based lubricant is a common choice as it doesn’t evaporate once applied. Oil-based lubricants are not recommended, as they can cause rubber components to degrade.

Remember to wear gloves and make sure to follow the instructions carefully.

3. Drive Belt Is Loose

The drive belt is distinct from the treadmill deck’s belt. The drive belt runs between the motor and the first roller underneath the deck. It’s essential that this belt works properly, as it’s what transfers the motor’s power to the deck.

Sometimes, the belt will slip and stop running, while the motor continues. This suggests that the front roller could be a problem and needs some lubrication or to be realigned.

Sometimes, the roller and pulley that drives it will also stop. This is a sure sign that the drive belt needs some attention. Even if the deck belt keeps running, you may feel the belt slip and shudder.

You can try to treat the drive belt with a belt dressing, which is like a lubricant. But it’s safer to just replace this belt because tightening it incorrectly or too much can cause damage to the expensive machine parts.

4. Pulley on the Front Roller Lost Grip

Sometimes the slipping of the treadmill belt can be caused by the belt literally slipping off of the front roller. The front roller is the driving roller, and if it gets out of alignment, it can stop the whole belt from running.

You’ll know this is happening when the belt stops, but the drive belt and pulley keep going. To fix this, you need to realign the pulley and the roller tube underneath the belt. The easiest way to do this is to stick a strip of colored tape from the pulley to the roller in a straight line.

Turn on the treadmill and wait for the belt to slip again. Once it does, switch it off and check the tape. If it has separated, then it’s a sign that your roller and pulley are misaligned. If not, then you need to look for another cause.

Sometimes, all it needs is for the pulley to be tightened. Other times it may need to be replaced. You can examine it to see which looks likely and it may be best to bring in a professional.

5. Belt is Worn Out

The treadmill belt could also be slipping because it’s had a lot of feet pounding on it and it’s just worn out. It does happen, especially if you bought your machine second-hand, use it a lot, or have multiple people in the household who use it.

If you lubricate the slipping belt and it doesn’t help, or it makes the slipping worse, then your best bet is to replace the surface belt altogether.


You can’t put a price on safety, and a slipping treadmill belt has the potential to cause severe injury. It’s better to spend some time and effort figuring out the problem and investing some time and money into fixing it, rather than ignoring it and suffering a fall later on.

If your treadmill is under warranty, be careful about replacing parts by yourself. From the smallest treadmills to the largest, there’s some fragile machinery inside. Some companies won’t be sympathetic if something goes wrong.

Photo of author


Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.