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By Simon Gould

Apart from the motor, the treadmill belt is probably the most important part of the machine. It is the part that has contact with the motor, which the motor pushes round to get the speed you want. It has contact with the deck, where there should be no dirt in between. It also has the contact with your feet as you do your running routines.

How to tell if the belt is worn out

If the belt is worn out it doesn't means you need to replace the treadmill, belts can be replaced just like other components of the item can. First you need to evaluate if your treadmill belt is worn out. What you need to do is run it at a very slow speed without you getting on it and look at the edges to see if they've curled up or are frayed.

Next have a look at the seam to see if any part of it is ripped or frayed too. This is a vulnerable area of the belt so problems are likely to occur here first so have a good look. Turn the treadmill off and unplug it and lift the belt up with your hands and there should be 3 to 4 inches of give. If there's more then tighten the belt using the screws at the end. Keep an eye on this to ensure the belt hasn't lost it's rigidity.

If it does need to be replaced then check to see if your treadmill is under warranty. If so talk to customer service at the manufacturer and organize the repair. If not they still may be able to help you or choose a repair man of your own. Don't try to fit the new belt yourself if you're not experienced enough. It may void the warranty and you may damage the treadmill.

If you're considering replacing the belt yourself, Amazon do a wide selection of treadmill belts* and your make and model could be there.

Further signs the belt is worn out

The belt slipping - There could be a number of reasons for a belt to slip, but one of them is it's worn out. There should be a few inches of give if you lift up the belt with your hand. The belt is lubricated so it needs to move over the deck but it shouldn't slip from side to side. Using an Allen wrench, turn the bolts at the rear of the deck clockwise to tighten the belt and anti clockwise to loosen it.

A smooth belt - An old belt which has had a lot of use will be a lot smoother than a new one. It's a sign the belt has had to much wear and may need replacing. You need to check not just the part of the belt you can see, but the underside of the belt that meets the deck. Run your hand along it's length to feel the smoothness and any fraying.

Damaged deck - If the deck is damaged, it could affect the belt. The belt needs to go round a smooth deck and any damage can affect that. I recommend an annual inspection by a treadmill technician. Here a professional can look at the belt and determine it's condition. If he decides it needs to be replaced, it will cost around $300 to get it done.

Remember to check the full length of the belt. You can do this by turning the treadmill on to it's side. Or you can make the belt do a couple of half revolutions. This way you're seeing the entire belt and you can make a good assessment as to whether it needs replacing. Do these diagnostics after you've lubricated the belt as it's a common problem.

When to call a professional

If you're unsure if the belt is worn out, but it keeps slipping or slowing down we you get on it, you may need a professional to diagnose the problem. If you're unsure of how to replace the belt then obviously an expert is needed. If you're unsure the belt is the problem and you've lubricated it, then you may need a house call.

These repair companies are always happy to help over the phone or email. If you email a picture of the belt, they might be able to identify if it's worn or see a different problem. Some belts can last a lifetime of the treadmill (10 years), although if it gets a lot of use, that time could be shorter. Therefore, if after 2 years you encounter a problem, it could be unlikely the belt has actually worn out.

A replacement belt including labor will cost around $300, so you need to consider if it's cost effective for you. If you've got a very old treadmill that's had many repairs in the past, you may consider buying a whole new one. This is especially the case if the deck is damaged and causing the belt to wear out quicker. Talk to a professional technician about whether he thinks another repair is viable.

Maintaining the belt

I'll go through the worn out question but first you should maintain the belt regularly. This is due to it's importance. A regularly maintained belt can extend the life of the treadmill by years. A treadmill can last up to 10 years if looked after properly. So you need to clean the belt every 2 weeks or so and lubricate it every 3 months. These both depend on how often you use it. Here are some guides:

• How to clean a treadmill belt
• Lubricating your treadmill
• Can I use household lubrication on a treadmill?

Thinking of buying a treadmill? Here's my favorite, I always recommend it when asked*