Treadmill Belt Is Slipping: Causes And Solutions

The treadmill is one of the best cardio and calorie-burning equipment to have in your home gym. Thanks to its ability to provide a relatively safe and effective cardiovascular workout.

However, treadmills have their share of challenges like any other workout equipment. One common problem with treadmills has the walking belt slip to one side while running. This makes it difficult to use the machine comfortably and affects the effectiveness of your workouts.

Luckily, if you know how to fix a slipping treadmill belt, you can easily solve this problem. But, if you don't, trying to fix the issue can be very frustrating.

Don't worry, though! In this guide, I'll show you some common causes that may be causing your treadmill belt to slip. More importantly, I'll include a solution(s) for each problem!

Let's get started!

Why Does My Treadmill Belt Slip? Common Causes & Solutions!

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Several factors may be causing the running belt of your treadmill to slip. Similarly, various ways to troubleshoot the problem, depending on the actual cause. However, some problems may be a bit more complicated to fix than others, based on the machine's age, condition, and brand.

Here are some common issues that are probably causing running belt slippage in your treadmill!

1. Inadequate lubrication

Improper lubrication is one of the major causes of treadmill belt slippage and the easiest problem to fix.

A treadmill deck is designed to slide over a series of rollers for the machine to work smoothly. This motion generates friction between the rollers, deck, and belt that must be reduced for a smooth operation. If there is inadequate lubrication, the friction generated between these parts will increase. As a result, the treadmill slows down when running, becomes difficult to operate, and causes the belt to slip from time to time.

In addition, there are some types of treadmills out there that are advertised as 'no maintenance' fitness machines. This is intended to create the perception that you don't have to undertake any maintenance practices after buying these machines. If you fall victim to these claims and fail to maintain or lubricate your treadmill regularly, the treadmill belt will certainly start to slip over time!

Solution: Regular treadmill maintenance lubrication

As mentioned earlier, improper lubrication is perhaps the easiest problem to fix if it's the main cause of your treadmill belt slippage. Besides, if you think that your treadmill belt skipping or slipping problem is due to inadequate lubrication, the solution is to lubricate it with a compatible lubricant.

But, how do I lubricate a treadmill? Treadmill belt lubrication involves various steps, including choosing the best lubricant.

In most cases, treadmill manufacturers recommend using silicone-based lubes to prevent the belt from slipping since it doesn't evaporate. However, some manuals indicate the specific lubricant recommended by the manufacturers. So, before you apply any lube to your treadmill belt, make sure you consult the manufacturer's manual first! More importantly, an over lubricated treadmill belt may increase the risk of falls & injuries.

As for 'no maintenance' treadmills, contact professional maintenance to ensure that your treadmill has proper lubrication. Also, check the user manual since the lubrication process tends to vary by model and brand.

Note, avoid using oil-based lubes to reduce friction in your treadmill since they can degrade rubber components in your machine. In addition, follow the instructions carefully and wear gloves while applying the lubricant.

2. Loose walking belt

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If proper lubrication isn't the cause of the treadmill belt slippages, the chances are that the moving belt is loose. The treadmill belt naturally loses its tension because of age and constant use. Once that happens, it experiences a lot of slippage during use.

Surprisingly, evaluating the tightness of the treadmill belt is very easy. Here's how you go about it;

Please turn off your treadmill and plug it out of the power socket; put your finger beneath the moving belt and lift it. If the belt leaves a gap of more than 2 to 3 inches, it's loose. More importantly, this may be the main cause of the belt slippage and needs to be repaired right away.

Thankfully, fixing this issue is quite simple since you only need to tighten the belt to increase its tension. However, it would help if you still were cautious since an over-tightened treadmill belt may cause strain on the drive motor to move the belt.

Solution: Treadmill belt adjustment/ tightening

Once you've ascertained that the treadmill belt is loose, please turn off the treadmill and unplug it. Put the Allen Wrench or hex key inside the rear roller bolt on the treadmill's back end. Most treadmills come with an adjustment tool you can use to tighten or loosen the slipping belt.

3. How to tighten the treadmill belt?

Give the adjustment tool a quarter turn clockwise to increase the belt tension. These changes should be made on both sides; one quarter turns at a time to avoid over-tightening the belt. As I mentioned earlier, over-tightening the belt will strain the electric motor or damage the belt and other expensive components. Also, make you check the manufacturer's manual for guidance on how to change the moving belt tension.

4. How to loosen the treadmill belt?

Repeat the process above but in reverse! Note, before adjusting the belt tightness, make sure you align it to the center!

Once you've adjusted the treadmill belt tension accordingly, lift it again with your hand to check its clearance from the running deck. According to experts, a belt with the right tightness should not lift for more than 2" from the treadmill deck. If the clearance is still more than that, continue the adjustment process until you achieve the right tightness.

You can also check the treadmill belt tightness by sliding your hand under the belt and moving it to the center of the deck. If your fingertips are getting right in the center, the belt has the perfect tightness. But if the fingertips are going past the belt's center, it's too loose. Contrarily, if the belt is too tight, the fingertips will not get to the center of the belt.

After adjusting the belt tightness, plug in the machine and use it to evaluate its tension.

5. Loose motor drive belt

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Treadmills have 2 types of belts; the running belt and the drive belt. The running belt is found on the deck, while the drive belt connects the 1st treadmill roller under the deck & the electric motor. Therefore, the motor drive belt must work properly since it transfers the motor's power (torque) to the deck.

Besides, the whole treadmill running workout relies on the functioning of this belt. Although the motor may work properly if the power transmission belt is loose, worn-out, or weak, it will not drive the treadmill deck smoothly.

Unfortunately, the drive belt tends to loosen or wear over time. This affects the tension of the belt, preventing the equipment from running smoothly. Also, this will cause the drive belt to slip and stop running, causing the treadmill belt to slip as well. More notably, the treadmill belt will continue slipping now and then until you solve this issue!

Solution: Drive belt replacement

Although tightening a loose drive belt is relatively easy, it's not recommended since you may end up over-tightening it. Incorrect tightening of the drive belt may elevate the operating amps, strain the motor, or damage some expensive treadmill components. Therefore, the best solution is to replace the loose drive belt to ensure that you don't add extra strain to the motor. Alternatively, use a belt dressing spray to treat the machine's drive belt for a temporary fix.

The drive belt is installed inside the electric motor hood cover. Before you replace this belt, check the user manual since some treadmill manufacturers prohibit the removal of the hood cover. Also, some manufacturers don't recommend performing this kind of treadmill repair since it often voids the warranty.

6. Worn-out belt

Even the best treadmill belts tend to wear out with enough usage. This is particularly common if you purchased a second-hand belt, train on the treadmill a lot, or have many people in the household using the machine.

The belt will start to slip when it wears out, causing treadmill runners to slip in the middle of their workout. Dust accumulation is another factor that can cause the belt to wear out quickly. For that reason, it's important to regularly clean the belt to avoid damaging the materials of the treadmill belt.

Solution: worn-out treadmill belt replacement

Sometimes, a simple solution like lubricating the treadmill drive belt, pulleys, and rollers may prevent a worn-out belt from slipping. However, if reducing friction doesn't fix the problem, you consider replacing a treadmill belt with a new one. Alternatively, you can call in your treadmill manufacturer's warranty service for worn-out belt replacement.

7. Lost grip on the front roller pulley

The last reason that may be making your treadmill belt slippage is if there is no grip in the front roller pulley. This pulley plays an important role in handling the weight on the moving belt and helping it complete the operating cycle. However, if the belt is slipping, the front roller and the pulley will be misaligned. Consequently, the running belt will misalign, causing it to slip over time.

Solution: Repair the pulley/ replace the roller

To determine if the treadmill belt is slipping due to the misalignment of the roller and the puller, turn off the machine. Next, attach a piece of treadmill belt repair tape on the part of the pulley you can see and attach another piece to the roller tube. Alternatively, draw a straight line from the roller tube to the pulley with a permanent marker.

Now, switch on your machine and check what happens when the moving belt slips. If the pulley & drive belt continues to move while the front roller & treadmill belt stops when running, the pulley has certainly lost its grip.

If you're still unable to confirm what happens when the treadmill belt slips, check whether the drawn line or tape separates. If the straight line or tape is still not separated, the roller and pulley are turning together. Therefore, the treadmill belt slippage may be occurring because of another reason. But if they've separated, the pulley is loose, so you either need to replace the roller or repair the pulley!

However, if you think this is beyond your technical comprehension, look for assistance from a professional technician.


Treadmill belt slippage isn't a big issue since it doesn't necessarily mean something is wrong with your machine. Nonetheless, if it happens frequently, it can cause severe injury to the treadmill owner or user. For that reason, it's important to find out the cause of the slippage and fix the problem as soon as possible.

Thankfully, now that you know some of the things that may be causing that to happen, it should not be that hard. Best of all, I've suggested some easy fixes that will help you solve these problems. However, some solutions may be complicated, so you may need to contact a technician to fix them. Moreover, you can easily avoid some of these issues by regularly taking care of and maintaining your treadmill.

Frequently Asked Questions

1. How to center a treadmill belt?

To center the treadmill belt, you'll need an Allen key that fits in the machine's rear roller bolts. Turn on the treadmill at the lowest setting and check for gaps between the rear roller and the belt's end. The gaps should be as equal as possible. However, if the treadmill belt moves away from a certain direction or is misaligned, the gap is usually smaller and vice versa.

Once you've determined where the misalignment is, use the left bolt on the rear end to adjust the alignment. If the roller and the belt gap is smaller on the left side, tighten it by turning the left bolt clockwise. On the contrary, if that gap is smaller on the right side, loosen the left bolt by turning it counterclockwise.

While centering the belt, turn the lefty bolt slowly and in increments of Ā¼ turns. And once you make each turn, wait about 10 - 20 sec for the turn to take effect. If the roller and the belt gap is still unequal, turn the bolt against it until the alignment is perfect.

2. How often should one lubricate the treadmill's running belt?

As per treadmill manufacturers, the running belt should be lubricated every 6 - 12 months. However, this tends to vary depending on the kind of treadmill lubricant and treadmill model.

3. Can you use WD40 as a treadmill belt dressing?

Yes! WD40 is a specially designed spray that works well as a belt dressing for treadmill belts. It penetrates the cord fibers of the belt, thus restoring its elasticity and flexibility.

4. How long does the treadmill belt last?

The durability of a treadmill belt usually varies depending on the maintenance, frequency of use, and type. For instance, a 2-ply running belt lasts about 5 - 10 years. Contrarily, a 1-ply treadmill belt lasts about 3 - 5 years or 300 - 500 hours.

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