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What Do Lawn Mower Tire Numbers Mean?

There are circumstances where you’ll have to replace the tires on your lawn mower, and in those instances, you’ll need to know the exact size of those tires. That being said, the numbers on the sides of the tires, which each mean something different, can help you with this, but only if you know exactly what the numbers mean.

While some lawn mower tires have two numbers on them, others have sets of three numbers. The main reason why those numbers are there is to tell you what size replacement tires you need to buy, but you have to know what you’re looking at first. That’s what this article is here to help you do.

Just the Basics

The numbers listed on the sides of tires give you information on their size, their ply, and their road-worthiness. For the basics on what to look for, here are a few descriptions based on whether the tire uses a two-digit or a three-digit system:

  • In a two-digit system, the first number describes the width of the tire and the second number is the tire’s rim diameter size.
  • In a three-digit system, those numbers are the same except that they are preceded by a number that tells you the diameter or the height of the tire whenever it’s inflated (but not when it’s carrying a load).

For instance, if a two-digit system is used on your tire and the numbers you see look like “9.5-8,” this is referring to a tire that is 9.5 inches wide and has an 8-inch diameter. If the tire you have uses the three-digit system, the numbers mean the same, but it will look something like “18 x 9.5-8,” which means that the tire is 18 inches high, 9.5 inches wide, and 8 inches in diameter.

Sometimes you’ll see these numbers are followed by the letters NHS. When this happens, it means that the tires are only for non-highway service. In addition, the maximum tire pressure is also sometimes located on the side of the tire.

Tire pressure is always measured in pounds per square inch, or PSI. This number indicates how much air you need to put into your tires. That being said, keep in mind that lawn mower tire sizes are always measured in inches.

Other Numbers Considered Important

In addition to the numbers that indicate the size of the tire, you may also notice ply rating number and a number that indicates the type of tire it is. The ply rating, which is usually indicated by numbers such as A/2 ply or B/4 ply, refer to the way the tire should be used to keep the passengers safe. For instance:

  • Tires marked A/2 ply should only be used on smooth, level lawns
  • Tires marked B/4 ply, because they’re a bit thicker and stronger, can be used on rugged or uneven terrain.

Yet another factor to consider is the tire tread pattern on the tire itself. If you notice treads shaped like chevrons, these are turf treads and work well on wet grass because they provide just enough traction to mow the lawn without damaging the turf. If you notice knobby treads that have deep grooves in them or a herringbone pattern, they are what you’ll need for mud or dirt lawns.

On the other hand, a ribbed tire usually doesn’t provide a lot of traction, which is why they are often found on zero-turn mowers. If you frequently use a trailer to move things around in your yard, the all-terrain treads mentioned above should be chosen.

Why does the tread of the tire make a difference? Because if you choose replacement tires that have a different tread than the remaining tires on your lawn mower, your grass may be cut unevenly. It seems odd that the treads of your tires are that important, but they are.

Even though you’ll need to know what the numbers on the sides of your tires mean before you rush out and buy a replacement, you’ll also need to take into consideration the tread pattern itself. Using tires with different tread patterns on your lawn mower can make the grass look patchy and unattractive.

Some Final Thoughts

All of this advice won’t do you much good if you don’t take good care of your tires before they need to be replaced. A good set of tires for your lawn mower usually lasts around five years, but that timeframe could be shorter if you’re regularly mowing rough terrain. Always make sure that you check the tire pressure regularly and keep them at the proper pressure at all times. While all four tires don’t necessarily need the same PSI, the back two tires and the front two tires should.

When storing your lawn mower, make sure that it’s stored out of the sun so that the sun doesn’t cause the tires to dry rot over time. Lawn mowers should always be stored either in a garden shed or somewhere in the shade.

Watch out for any cracks or even nails that might have become embedded in the tires and take care of the problem before you use the lawn mower the next time. Finally, when you wash your lawn mower, never use cleansers that are too harsh because they can ruin the tires on the mower faster than you think.

Finally, most experts recommend rotating the tires on your lawn mower every 6000 miles or so. You can either do this yourself or trust the job to a lawn equipment shop. Lawn mower tires are much the same as the tires on your car. You can’t ignore them, they need regular maintenance and care, and you have to replace them whenever they become too torn and worn out.

While it always starts with making sure that you replace the tires with other tires of the right size, you can see how there’s much more to it than that. Fortunately, most of the things that you need to do to keep your lawn mower tires in great shape are easy to do and inexpensive, so there’s no need to stress over their care.

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