When To Replace A Lawn Mower Belt? Find Out Here!

Written By James
Updated July 24, 2021 by James

When To Replace A Lawn Mower Belt? Find Out Here!

How Often Should I Replace a Lawnmower Belt?

The belts on your lawnmowers are important parts, as these are responsible for the pulley turning system on your machine are essentially what allows the mowers blades to rotate. 

There is no correct belt replacement time, as a belt replacement can occur at different times for users depending on how often they use their lawnmower. On average this tends to be around 3-4 years, but a simple deck belt can break due to other factors such as a faulty pulley system too. 

No matter what, as soon as your deck drive belt breaks, it will need replacing, and changing it can be complicated if your a newbie too mowers, so we have put together an informational guide that will tell you the hints you need to replace your mower belt and how to do it. 

What Is a Lawn Mower Belt? 

Lawn mower machine belts come in two types; the drive belt and deck belt. The deck drive belt is very important as this is what makes the engine drive pulley system work and allows the lawn mowing movement to work, when broken the mower might not move at all. 

The deck belt on the other hand is not removable and tends to be internal on the lawn mower, this is what allows the blades to spin on the machine for cutting your lawn.

Some lawnmowers may even have a deck drive belt that extends up and acts as both an engine drive pulley and blade turning system.

Symptoms Your Lawn Mowers Belt Needs Replacing 

Trying to see whether or not you need to replace your lawnmower machine belt before it breaks can be difficult, but there are a few common signs that would indicate you could be dealing with a broken belt soon. 

We have listed some signs which often indicate you will need to replace your belt drive below. 

  • Glazing - If your machine belt on your mower deck has developed a shiny surface, this is not good for traction when using the mower and will often cause nasty vibrations when the lawnmower is in use.
  • Sidewall damage - Any damage on the edges of your deck drive belt will show it needs to be replaced as there is a matter of time before this damage spreads, resulting in the whole belt breaking. 
  • Cracking - Often, on low-quality belts, they can crack and become brittle, you will need to change the whole belt unit if this happens to you, it's always best to invest in a top-quality drive belt if you can.
  • Fraying - Any wear and tear or fraying of the belt edges will indicate its time is up.
  • Flat spot - Flat spotting on your basic quality belt will happen if the mower blades get stuck and the engine pulley system continues to run with the belt, this will grind the belt, encourage flat spots and vibration at the whole mowing deck.
  • Blistering - Blistering spots are generally common on older lawnmower belts and are normal wear, when left these can become larger so need to be dealt with a soon as they are seen which is likely by replacing the whole belt. 
  • Slowing down and squealing - Apart from visually inspecting the mower belt itself, you might also find the machine slowing down during use or making a screeching noise, tension can additionally loosen unexpectedly from the drive belt during use. 

Factors To Consider Before a Deck Belt Replacement 

A deck belt replacement can be carried out by any lawnmower owner with the right steps, but you should get to know your mowers belt first, so as you can ensure you are replacing it with the correct belt and understand the belt routing of your specific model. 

We have listed some of the most important factors you should consider about your broken mower belt before getting into the replacement process. 

  • Figure out your cutting deck - Firstly, no matter what kind of mowing deck your lawnmower has they are all related to the engine crankshaft on the machine. Look to see whether or not you have a timed deck (which is a little difficult), mulching deck, rear discharge deck or side discharge deck. 
  • Measure the belt size - A V belt width should fit perfectly into the pulley belt unit, if not it is worn out, you can see the width, inside length and outside length of your mowers belt by looking at its side where it is written, however, if yours has worn away, you will need to measure yourself or contact the manufacture. 
  • Check the belt routing - Take pictures of how your old mower deck belt is set up beforehand so as you can familiarise yourself with the pulley system and how it works, some mowers belt guide can go on backwards, so know the routing of the correct belt.
  • Look for pulley signs of wear - Pulleys are responsible for transferring engine pulley power, this often wears out at the same time as your belt. 
  • Decide the source belts type - Fitting the wrong belt on your mower deck belt setups will cause a lot of issues, you can find AA hex belts, A-type belts, B type belt, and a timed belt. These will also come in the two main types of a toothed belt and a V belt as well as AA hex belts. 

How To Replace Your Lawn Mower Belts

Now we know all the essential information about when to replace your lawnmowers belt and factors you should be considering before you start the replacement, let's get on to how to do it when it comes to fitting belt types. 

We've composed a basic step by step belt guide to changing the belt on your lawn mower deck below, avoid choosing low-quality replacement belts, as they will snap again easily and be confident your replacement lawnmower belt type is of the right size and make.

  • Step One - Turn your lawnmower off, set it on a flat surface and disconnect the spark plug to stop any accidental start-ups during the replacement, adjust the mowing deck height to the lowest setting possible. 
  • Step Two - Remove the belt deck guards, covers and rods on a level surface and loosen the idler pulley nuts, you don't need any special tools to do this. 
  • Step Three - Snap a photo so as you can remember the engine pulley belt routing system then remove the belt from the idler pulley nuts. 
  • Step Four - Now install your new belt in question, make sure you route it the right way following the picture that you took and ensure the spare belt is of the right type, whether that's a V type or toothed belt. 
  • Step Five - Tighten everything you loosened such as the mower belt idler pulley nuts, belt idler arm rod, and covers and check belt tension.
  • Step Six - Raise the mower deck height back on your mower, insert the spark plug wire back in and take your mower with its new belt type for testing. If you hear any weird sounds when you operate your mower with your new belt on the grass then you may need to undo the screws and pulley bolts again to have a look.

Frequently Asked Questions About Replacing Lawnmower Belts 

Can a drive belt break from tall grass? 

Tall grass does have the potential to break complete belts on a lawnmower as it can get tangled around the pulley system causing the belt to snap.

How to fix loose belts on a lawnmower? 

If you keep having loose lawnmower belts or faulty belts with bad tension then you will need to adjust the belt tension assembly on your mower, luckily this is quite straight forward and you don't need any special tools. 

What type of lawnmower uses common V belts? 

V belts are most commonly used on lawn tractor belt mowers and tend to be quite heavy-duty.

Final Words 

Overall, a lawn mower belt will need to be replaced according to your judgement and will come down to how often you use your lawnmower and how heavy-duty your grass is that you use it on.

On average, this will be after around three years, but you can use our common symptoms above to see if you have any of the replacement signs. 

To replace the belt on your lawnmower you can simply follow the steps in our guide above, but remember to route the belt correctly and use the right size.

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My father, and his father before him, and his father; for the past 3 generations, my family have always been into gardening. The green fingers is a gift passed down to me and I thoroughly enjoy it! I also have worked in the manufacturing department for Bosch and DeWalt so I like to think I know a thing or two about tools and such!
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