18x8.50-8 18x9.50-8 Lawn Mowers Tubes with TR13 Straight Valve Stem,Heavy Duty Replacement Inner Tubes for Garden Trailer Tractor Golf Cart

What It Is

These are heavy-duty replacement inner tubes designed for pneumatic tires on lawn mowers, garden trailers, tractors, and golf carts. They use a TR13 straight valve stem, which is the standard automotive-style stem for most mower and trailer wheels.

Fitment & Compatibility

Before buying, confirm your tire size. This listing covers two sizes: 18x8.50-8 and 18x9.50-8. Both fit rims with an 8-inch diameter. The 18x8.50-8 tube is narrower and fits tires up to 8.5 inches wide; the 18x9.50-8 tube is wider and fits tires up to 9.5 inches wide. Use the wider tube if your tire is close to 9.5 inches wide—it will still fit a narrower rim and provide better puncture coverage. Check your current tire sidewall for the exact size marking (e.g., “18x8.50-8”). These tubes are universal fit, not OEM-specific, so they work with any brand mower, tractor, or cart that uses those tire sizes. No need to match deck size—just tire and rim specs.

Key Things to Know

• Heavy-duty construction – Made from thicker rubber than standard tubes, reducing pinch flats and puncture risk. Good for rough terrain or heavy loads.
• Installation is straightforward – You’ll need basic tire irons and a pump. Lightly inflate the tube before inserting to prevent twisting. Watch the valve stem alignment—the TR13 stem is straight, so it must align with the wheel hole.
• Common gotcha – Using a tube that’s too wide (e.g., 18x9.50-8 in a narrow 18x8.50-8 tire) can cause bunching and potential chafing. Stick to the size that matches or is slightly wider than your tire’s maximum width.
• Valve stem compatibility – The TR13 stem fits most mower wheels, but check your wheel’s valve hole diameter. If it’s a smaller or angled stem hole, you may need an adapter.

Should You Buy It

If you need a reliable, heavy-duty tube for an 8-inch rim in a lawn mower, garden trailer, or golf cart, this is a solid choice. It’s affordable, well-rated, and easy to install. Avoid if you have a non-standard valve stem angle or need a tube for a different tire size.