lawn mower is cutting unevenly

My Lawn Mower Is Cutting Unevenly (Why + How To Fix It)

If you’ve been getting less than perfect results when cutting your lawn, you’re probably feeling a little frustrated. We all want our lawns to look perfect, neat and even so when your lawn mower is cutting uneven, you’ll need to do a little detective work. But what causes uneven grass cutting?

Your lawn mower could be cutting uneven for a variety of reasons. This could be down to the tire pressure or wheel damage, issues with the blade, or a clogged mower deck.

But don’t despair, most of these things are super easy to fix and we will have your lawn mower up and running again in no time, cutting evenly and neatly, just as you want it to.

Damaged Wheels

No matter what kind of lawn mower you are using, it’s super important to make sure that all of the wheels are in good working order. If they’re not then you’re going to notice that the lawn mower becomes incredibly difficult to use. With a push mower, you’ll find it more difficult to move your tool around and with a riding mower, it’ll be tricky to drive.

What’s more, when one or more wheels are damaged, this will cause the lawn mower to tilt to the affected side and this is what causes that uneven cut.

To determine if this is the problem, you will need to observe the mower in action. If you can see any of the wheels wobbling then there’s a good chance that there is damage. Usually, this will mean replacing the wheel.

Wheels Are At Uneven Heights

While there are lawn mowers that have a central height adjustment mechanism, many require the user to adjust each wheel individually. If one wheel is set slightly differently to the next then you’ll find that you end up with a drastically uneven but. Even the slightest difference can have a big effect.

It’s also important to be aware that, even if you set the wheels to the same height in the first place, one may fall out of place. This is especially true if the system is particularly flimsy or weak so it’s worth checking the wheel heights before using the mower to make sure they’re all where they need to be.

Mower Deck Is Damaged Or Uneven

Your mower deck takes quite a bit of a beating every time you use your mower and over time, this can result in damage. Normally, this will be in the form of small holes and if you have a metal deck, corrosion can become an issue.

When there is damage to the lawn mower deck, this can impact the vacuum effect under here and the result is uneven grass cutting.

You can attempt to repair the mowing deck and fill any holes that may have occurred. However, it isn’t always possible to just patch up the problem and you might just have to admit defeat and invest in a new lawn mower.

Clogged Mower Deck

When you think about the underside of your lawn mower, you could be forgiven for thinking that the only important part of it is the blade. Yes, this is a terribly important part but the actual mowing deck is just as essential in the running of your lawn mower. This is because it creates a vacuum which causes the blades of grass to point up, making them easier to cut; and everything is kept even.

However, if you don’t take the time to clean your lawn mower deck then it will become clogged with grass clippings and debris. These can interfere with the vacuum and you’ll end up with a less than even finish to your lawn.

If your mower deck is clogged then the best tool to use is a putty knife but be aware that you will need to put in a good degree of elbow grease as well. But prevention is better than cure so always make sure to clean the mower deck after using your tool. There are even products you can spray under the deck to stop grass from sticking to it.

Loose Lawn Mower Blade

If you don’t give your lawn mower the correct maintenance then it’s not going to stand the test of time. One of the parts that is often neglected and then suffers is the blade, particularly the bolt that secures it to the crankshaft. When this loosens, the blade doesn’t retain its horizontal position which can affect how it cuts.

The blade needs to be 100% in the correct position and even just being slightly off can make a world of difference to how even the cut is. You’ll be able to tell whether a loose blade is the problem by listening to your mower when it runs as you’ll be able to hear rattling.

You can also tip the mower onto its side and inspect the blade. Make sure to disconnect the power and wear protective gloves because, even though the blade may be loose, it’ll still be sharp.

Now hold the blade by the back edge and take a look at whether it moves vertically at all. If it does then this will tell you that the blade is loose. The fix is pretty simple and all you’ll need to do is grab a wrench and tighten the bolt back up.

This is also a good opportunity to check whether the blade needs to be sharpened. If it does, you should get onto it right away as this is another reason that your lawn mower might be cutting unevenly.

Lawn Mower Blade Is Bent

If you have a lawn mower that isn’t delivering an even cut then the issue could be a bent blade. This happens when you run the mower over something solid such as a piece of metal or a rock. When the blade is bent, the results are similar to that of a loose blade as the whole thing will be knocked out of alignment.

There are websites out there offering advice on how to straighten your lawn mower blade if it becomes bent. However, this isn’t something that I would highly recommend. You see, it’s almost impossible to get it back to how it once was unless you’re a real pro.

All you’ll end up doing is wasting time so it’s much better to just admit defeat and replace the blade. Moreover, using a bent blade is dangerous and can cause further damage to your mower so it’s just not worth it.

Mower Blade Is Dull

Over time, using your lawn mower is going to take its toll on the blade. There’s nothing you can really do about that, it’s inevitable. However, keeping your lawn mower blade sharp is one of the best ways to ensure it cuts well.

When you use the mower, dirt and debris fly around the deck and wear away the edge of the blade. If this isn’t dealt with then it is possible that the blade will miss strips of grass leaving you with an uneven finish.

While you cannot stop the blade from wearing, it’s important to periodically check it and sharpen it when needed. Eventually, you will need to replace your lawn mower blades as there’s only so many times you can sharpen them.

Crankshaft Is Bent

In cases where you have noticed that the blade is bent, it may also be that the crankshaft is bent. When you install a new blade, this isn’t going to solve the issue and in reality, bent crankshafts are not good news

In order to tell whether this is the problem, you will need to check your mower. Make sure that you disconnect the power and then turn the mower over so that you can see the blade. Give the blade a spin from the back edge and then look at the bolt that connects it to the crankshaft. If this wobbles then it’s a pretty obvious sign that the crankshaft is bent.

But we have some bad news. If the crankshaft is bent, it’s time to buy a new lawn mower. That might not be what you want to hear but there is no way of fixing this problem so unless you want to carry on having uneven grass then you’ll need to make the investment.

What’s more, it’s actually very dangerous to use a lawn mower with a bent crankshaft as it could break and send the blade flying which could result in a serious injury.

Uneven Weight Distribution

One of the most common reasons that a lawn mower might be cutting unevenly is because of uneven weight distribution. Just check this to make sure that everything is even and make adjustments where necessary. You’ll likely find that this solves your problem.

Riding Mower Cutting Uneven

riding mower cutting uneven

If you have a riding lawn mower then the reason that it is cutting unevenly is more often than not due to issues with the tire pressure. When the wheels are not even, this can cause the lawn mower to tilt to one side resulting in an uneven cut.

Take a look at the grass after cutting and if you notice a wonky step-like pattern the cause is probably uneven tire pressure. But fortunately, the solution is incredibly simple and all you’ll need to do is check the tire pressures and adjust them as needed.

However, do keep in mind that, over time, your tires will wear and there will come a point that you won’t be able to inflate them anymore. This may be because of wear, age or a puncture but in any case, you will need to replace the tires.

Final Thoughts

Having an uneven grass cut is mighty annoying and can leave your lawn looking less than manicured. However, the reasons that your mower might be causing this issue are usually pretty simple to fix.

Things like deflated or uneven tires, dull blades, or an uneven mowing deck are often the cause of the problem. There are a couple of things, such as a bent crankshaft, that may mean you need to replace the entire mower but for the most part, you’ll have that beautifully even cut back with a quick fix.

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Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.