Why Do My Lawn Mower Tires Keep Going Flat?

If your lawnmower tires have taken on the appearance of mushrooms flipped over on their head, you’re probably dealing with a slow leak at the very least. The worst part is, you fill the air back in, and they resume their mushroom look not two days later. So why do lawn mower tires keep going flat?

If your lawnmower tires keep going flat, you probably have a slow leak either because a foreign object has penetrated the tire wall or your valve stem is faulty. Of course, you could blame a rough lawn or heat exposure, but these are usually secondary factors to a more pressing problem.

If you have brand new tires on your lawnmower with the maximum PSI,

excess heat and a rough lawn aren’t going to flatten them, at least not overnight. These factors will contribute to an existing slow leak. However, those aren’t the only reasons you keep experiencing flat tires. 

Factors That Might Cause Repeated Flat Lawnmower Tires

You could consider excess heat and rough lawns as causation behind tires that go flat in roughly a month or so, but not daily. If your lawnmower tires keep going flat and they’re doing so quickly, you have a slow leak. 

Going flat over long periods of time means that you need to focus more on preventative maintenance. 

  • Too much exposure to the sun or excessive heat in storage
  • Overall wear and tear that occurs over the life of the tire
  • Rough, bumpy, or otherwise difficult lawn terrain
  • A damaged or comprised tire wall or tread 
  • Your valve stem is faulty

This can all sound confusing, but we’ll take a closer look at each one in more detail to help you uncover the issue.

Sun Exposure and Excess Heat

Both of these kinds go hand-in-hand. For example, exposure to the sun on its own hastens the effect of dry rot, cracking, or severe weathering on the portion of the tire that is constantly exposed to it. 

Avoid storing your lawnmower so that the sun penetrates it for long periods. For example, store it in the garage, basement, or storage building to protect it from the elements.

If you have no choice, you can invest in a lawnmower tarp or something similar to keep it covered up when you’re not using it. While sun exposure will not make your tires go flat overnight, it will significantly shorten the tire’s lifespan. 

Excess heat is an issue as well, and it’s something that can be mitigated by covering your lawnmower as well. You can kill two birds with one stone just by keeping your lawnmower covered up or parked in a shaded area when it’s not in use. 

Heat causes air to expand, and if there is already a slow leak going on, whether in the valve stem or the tire itself is compromised, it will exacerbate the leak, possibly causing a critical failure which means a blowout. 

Wear and Tear Over Time

The natural wear and tear that occurs over time is at least something that you can expect, and if you regularly perform routine inspections or maintenance on your lawnmower tires, then this is something that you will catch as the tread wears down to nothing. 

You don’t want to wait until the tires or so slick that they just spin on wet grass before you get them replaced. Lawnmower tires, especially pneumatic and tube tires, are just like regular vehicle tires, and you can see when they’ve reached the point where it’s time to change them.

Difficult Terrain

If the areas that you have to mow are nothing more than hellish landscapes full of bumps, hardpacked clay, and plenty of ups and downs, you should consider switching to a more aggressive tire tread. You can find lawnmower tires that are seemingly built for ATVs

Aggressive tire treads will give you more grip on hills and smooth out your ride. 

Compromised Tire Wall

One of the most obvious sources of air loss in lawnmower tires is a punctured tire wall, whether a nail, staple, spike, or anything strong enough to puncture the tire and let all of your air out. 

A slow leak usually only occurs in pneumatic tires since these tires have air without tubes. Because once the nail penetrates the tire wall, the air pressure and mass of the rubber material squeeze tightly around the nail, holding it in and sealing it. 

When you have a tube tire, once the nail penetrates deep enough to puncture the tube, the tire will immediately go flat. This is because a tube won’t seal around the nail like a pneumatic tire would. 

Faulty Valve Stem

The valve stem is where you inflate and deflate the tire. It usually sticks out of the tire’s side, close to the rim. One thing most people neglect to do, whether in their personal vehicles or on their lawnmower tires, is replacing the cap on the valve stem, which you should always do. 

Damage to the valve stem is usually caused by corrosion and the aforementioned dry rot that comes with time and too much exposure to the sun, heat, or both. 

If it is dry rotting around the base of the valve stem, it’s a safe bet that you need to replace the entire tire.

How Much Air Pressure Should a Lawnmower Tire Hold?

Tire pressure is a matter of extremes. You don’t want too much air pressure, just like you don’t want too little, though having too much is often a recipe for more damage than the latter. 

The manufacturer imprints the recommended tire pressure (PSI) on the side of the tire wall. If it rubbed off at this point or you can’t read it, you should look up the tire manufacturer to get an idea of the correct air pressure recommendations. 

If you don’t know for sure, never hesitate to ask a professional. A few phone calls or a few moments of conversation may end up saving you a deal of money in the end. Keep your tire pressure at an optimal amount.

Proper Lawnmower Tire Maintenance

Preventative maintenance is the key to saving you a ton of money in the long run, and it’s the one thing that is arguably the most important of all because most people don’t practice preventative maintenance, and it’s entirely understandable. 

Many of us have hectic lives, and prioritizing preventative tire maintenance on our lawnmowers doesn’t often find its way to the top of anyone’s list. 

However, if you want to keep your lawnmower’s tires and everything else about the lawnmower in tip-top shape, then a routine inspection is the least you could do. 

  • Always store the lawnmower in a cool, dry environment or as close as you can get to one
  • Never wash the tires with harsh chemicals as they will dry out the rubber and cause a hastened, dry rot effect
  • Keep your tire pressure at the best, maximum pressure
  • Consider tube tires over pneumatic
  • Never park in the open sun, at least not for long periods
  • Replace your tires when necessary
  • Keep an eye on tire pressure periodically

Final Word

If your lawnmower is experiencing frequent flats, then the odds are that you have a slow leak somewhere or dry rot is taking its toll on your tires. If necessary, replace your tires and establish a good routine for tire maintenance and inspections.

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