How to Keep Lawn Mower Tires From Going Flat (6 Causes + Solutions)

There was a time when I would always have to refill the air in my tires before heading out to mow. For no obvious reason, like a thorn or nail sticking in the tire, my tires would always be flat. I was very confused as to what was going on. So, I stopped one of the lawn guys working in the neighborhood and asked if he had any advice for me. Since that conversation, my tires never go flat anymore. Let me share with you what I learned.

Why Are My Lawn Mower Tires Going Flat? (The Short Answer)

Tires don’t go flat just because of punctures. Lawn mower tires actually rely on several elements to keep the air in the tire, such as the tire, the tire bead, the wheel hub, the bead of the wheel rim, the valve stem, and the valve. A defect with any of these items can cause lawn mower tires to keep going flat.

Potential Causes of Lawn Mower Tires Going Flat (A Closer Look)

Let’s take a closer look at how and why your lawn mower tire keeps losing air. There are several different areas on your wheels you’ll want to investigate to figure out where the air is leaking from.

Puncture in the Lawn Mower’s Tire

The most common cause of lawn mower wheels staying flat is a puncture in the tread of the tire. I tend to pick up the odd thorn after trimming my bougainvillea bushes or a screw or two by the roadside. A hole in the thread of your lawn mower’s tire will definitely cause your tire to lose air.

So, take a look around the tire and see if there is anything sticking out that could be causing your tire to leak slowly.

Damage on the Tire Wall

The tire’s wall can suffer dry rot if your lawn mower is left out in the sun without any kind of tire protection. Dry rot will slowly break down the tire’s rubber and begin to form cracks. Once these cracks get deep enough, you’ll find your tires slowly start to lose air. So, take a close look at the tire wall and check for any cracks.

Tire Bead & Wheel Hub Bead Not Sealing

Inside the tire bead are a number of steel wires that give the bead a lot of strength and prevent it from overstretching once it’s installed. Then, on the wheel hub, there is another bead that the tire bead fits over. Once the tire is installed, both beads form an air-tight seal. This is part of the reason you don’t need inner tubes.

So, if either of these beads is damaged or obstructed, there will no longer be the necessary air-tight seal. Check that the tire’s bead is sitting on the hub’s bead and nothing is obstructing where the two parts meet.

Damage to the Wheel Hub

Next, you want to take a look at the actual wheel hub itself. Make sure that the hub and the hub’s bead are still perfectly round. I have seen a zero-turn lawn mower’s deformed front caster wheel that prevented the tire from holding air.

Also, check to see if your lawn mower wheel has any welds. Sometimes the inner part of the wheel hub is welded to the outer rim, and these welds can break and rust, causing an air leak through the rim.

Air Leaking from Around the Valve Stem

To make the tire tubeless, the wheel hub needs to have a valve stem installed with an air-tight seal. Now, the valve stem is normally tucked inside the hub and out of the way of danger. But this doesn’t always protect them from every potential hazard, like sticks and the sun.

So, if a valve has been jabbed by a stick or even sat in the sun and rotted, then it could be leaking. Therefore, take a close look and see if it’s leaking air between the valve stem and the wheel rim.

Air Leaking from the Valve

Last on the list of items to check if your lawn mower tire keeps going flat is the valve inside the valve stem. This little valve is the device that allows the tire to be filled and keeps air from escaping. There should be a valve cover that prevents any dirt from getting into the valve and blocking it.

Now, I know that sometimes we drop or lose these valve covers when we’re inflating our tires, or they break, and we can’t get them back onto the valve. If this has happened to you, then each time you inflate your tires, you’re blowing dirt into the valve. Once dirt gets in the valve, the valve can’t close properly, and the tire will slowly leak.

The Best Way to Find a Leak in a Lawn Mower Tire

For this test, I make a water and dish soap mixture and pour it into a spray bottle that I picked up at Home Depot for a couple of bucks. Then, I properly inflate the problematic tire and spray it with the soapy water. I make sure to cover the entire tire, hub, valve stem, and valve with the spray. If there is a leak, then the soapy water will begin to bubble.

Just remember that you might need to move the lawn mower while looking for the leak so that you can get to the part of the tire resting on the ground.

How to Fix a Slow Leak in a Lawn Mower Tire

As you can see, there are a few places where your lawn mower tire can leak air. So, now let’s figure out how to keep lawn mower tires from going flat.

Losing Air Due to a Puncture in the Wheel Tread

The best advice that the lawn guy gave me was to get hold of some heavy-duty tire sealant. This is basically a rubberized glue that sits inside the tire and seals any punctures as they occur.

So, if you get a puncture, the sealant is forced out of the tire when it loses air and then sets, sealing the hole. A lot of the time, you won’t even notice that you had a puncture and that it’s been repaired.

Another piece of advice the lawn guy gave me was to avoid products from the box stores and instead head to the lawn mower store and pick up a professional-grade lawn mower tire sealant.

So, let’s go over the steps you’ll need to follow to use a heavy-duty lawn mower tire sealant.

1. Chock the rear wheels of the lawn mower.
2. Raise the front of the lawn mower off the ground using a jack.
3. Remove the valve cores from both of the valve stems on each front wheel using a valve stem core removing tool.
4. Connect the heavy-duty sealer container to the valve stem of one of the front wheels.
5. Squeeze the heavy-duty sealer container and transfer the sealer into the wheel.
6. Repeat for the other front wheel.
7. Install the valve stem cores back into the valve stems.
8. Fully inflate the tires.
9. Lower the lawn mower and remove the chocks.
10. Drive the lawn mower for a few minutes to fully coat the side of the tires.
11. Repeat the process for the rear tires.

Tools & Parts to Install Heavy-Duty Tire Sealant

• Chocks
• Car Jack
• Valve Core Removal Tool
• Heavy-Duty Tire Sealant

Your Tire is Losing Air Through the Tire Wall

If you are losing air through the tire wall of your lawn mower’s tire, then you can use the same heavy-duty tire sealant as before. So, if you install a sealant for punctures in the tire tread, you’ll be covered for the tire wall. However, tire walls are much thinner than the tread, so sealant might work for a little while, but I’d expect the tire to blow pretty soon. Therefore, if your tire is leaking through the tire wall, then you should start looking for a new tire.

The Vale Stem Has an Air Leak

A leaking valve isn’t a big fix if you have the right replacement valve and the right tools. First, double-check the size of the valve stem you need because there are different ones available, and get yourself a valve changing kit. Let’s take a look at the steps.

1. Deflate the tire by removing the valve core.
2. Slide the valve hook between the valve stem and the valve opening in the wheel hub.
3. Turn the valve hook so that it hooks into the center of the valve stem.
4. Pull the hook from the wheel hub and remove the valve stem.
5. Take the valve pusher and connect a new valve stem to the shaft of the pusher.
6. Spray lubricant over the new valve and the valve opening on the wheel hub.
7. Place the valve funnel into the valve opening on the wheel hub.
8. Take the new valve, connected to the valve pusher, and place it inside the valve funnel.
9. Push the valve through the funnel using the pusher and into the valve opening.
10. Once the new valve is inside the wheel, pull the pusher and funnel until the groove on the valve stem end locks into place.
11. Remove the pusher and funnel from the new valve.
12. Inflate the tire.
13. Install the valve cap.

Tools & Parts to Replace the Valve Stem

• Replacement Valves
• Spray Lubricant
• Rubber Mallet
• Valve Core Removal Tool
• Valve Changing Kit
  • Valve Hook
  • Valve Pusher
  • Valve Funnel

The Valve Core Doesn’t Hold Air

If your valve core isn’t holding air, then you need to install a replacement core. If the valve still leaks air after you have replaced the valve core, then you’ll want to completely replace the valve stem. So, let’s take a look at how you can swap out your lawn mower’s valve core.

1. Unscrew the valve core with your valve core removal tool.
2. Screw your replacement valve core into the valve stem.
3. Inflate the tire.

Tools & Parts to Replace the Valve Stem

• Replacement Valve Core
• Valve Removal Tool

Lawn Mower Tire Leaking Around the Rim: What Should I Do?

If your zero-turn front tire keeps going flat because of a leak around the rim, or any other mower for that matter, then you’ll need to establish if it’s due to either a damaged hub or the bead not being seated correctly.

Unfortunately, if you have a damaged rim, you’ll need to purchase a replacement. So, let’s look at getting the bead seated and see how to keep your lawn mower tires from going flat.

The Tire Bead isn’t Seated Correctly

Sometimes, you might find that the bead of the tire isn’t sitting on the rim correctly and making the seal you need. This tends to happen if you run your lawn mower with a flat tire. Like when you try to get your mower back to the garage with a flat.

So, if you notice the bead leaking, you’ll need to get the tire back on the rim. Here’s what you need to do.

1. Jack up the lawn mower so that the flat tire is off the ground.
2. Remove the valve stem core.
3. Connect your tire inflator.
4. Spray the area where the bead is off with a spray lubricant.
5. Inflate the tire.
6. Press/squeeze/push the bead to form a manual seal.
7. Start inflating until the tire reaches maximum pressure.
8. Deflate the tire if the bead doesn’t pop into place.
9. Repeat the process until the bead pops into place.
10. Remove the tire inflator.
11. Install the valve core.
12. Inflate the tire to the required pressure.
13. Lower the lawn mower.
14. Install the valve cap.

Getting a bead to pop on can take some time. So, if you can, get hold of the biggest tire inflator you have available. I use an air compressor that can fill my tires very quickly. This definitely helps get the bead back on the rim.

And if you’re sitting there wondering, does tire sealant work on rim leaks? Well, in my experience, no, not really, unless it’s a small leak. If the bead isn’t on the rim, the sealant won’t do anything other than make a mess.

Tools & Parts to Get a Bead Back on a Rim

• Valve Core Removal Tool
• Jack
• Spray Lubricant
• Tire Inflator or Air Compressor