Lawn mower, ride-on mower, and garden tractor tyre sizes can seem confusing because small machinery utilizes two distinct sizing standards. The numbers molded into the rubber indicate three core measurements: overall tyre diameter, section width, and wheel rim diameter.

Selecting the exact size match is vital for deck alignment, ground clearance, and proper seating on the rim flange. Below is a breakdown of how to decode the two most common garden equipment sizing formats: 13x5.00-6 and 4.10/3.50-4.

Format 1: The 3-Number Direct System (e.g., 13x5.00-6)

The standard 3-number format (Diameter x Width - Rim) is common on ride-on mowers, turf tractors, and zero-turn mowers:

• 13 (Overall Diameter): The inflated height of the tyre from the ground to the top tread in inches (13 inches).
• 5.00 (Section Width): The width of the tyre from sidewall to sidewall in inches (5.00 inches).
• 6 (Rim Diameter): The diameter of the metal wheel rim where the bead seats (6 inches).

Summary: A 13x5.00-6 tyre stands 13" tall, is 5.00" wide, and mounts onto a 6" wheel rim.

Explore our range of garden equipment tyres for mowers, utility carts, and turf equipment.

Format 2: The Sidewall Ratio System (e.g., 4.10/3.50-4)

Common on wheelbarrows, hand trucks, wood chippers, and lighter garden equipment, this format uses nominal width and sidewall height rather than total diameter:

• 4.10 (Nominal Width): The approximate tread width of the tyre in inches (~4.10 inches).
• 3.50 (Sidewall Height): The height of the rubber section from the rim edge to the outer tread face (3.50 inches).
• 4 (Rim Diameter): The diameter of the metal wheel rim (4 inches).

Calculating Overall Height: To estimate total overall height for a 4.10/3.50-4 tyre, multiply the sidewall height by 2 and add the rim diameter: (3.50" x 2) + 4" = ~11 inches total height. This is why 4.10/3.50-4 is often listed interchangeably with 11x4.00-4.

Why Accurate Lawn Mower Tyre Sizing Matters

Installing an incorrect tyre size affects performance, safety, and equipment longevity:

• Mower Deck Alignment: An incorrect front or rear tyre height unlevels your mower deck, leading to uneven grass cuts and scalp marks on turf.
• Frame & Deck Clearance: Oversized widths or diameters can rub against deck belts, steering arms, or mudguards during sharp turns.
• Rim Bead Seating: Matching the final rim diameter number (e.g., 4", 6", or 8") is non-negotiable — a 6" tyre cannot be stretched onto an 8" rim.

How to Find and Read Your Tyre Size

Inspect the outer rubber sidewall on both sides of your existing tyre. Look for embossed numbers formatted in one of these three ways:

• 13x5.00-6 (Ride-on front tyres)
• 18x8.50-8 (Ride-on rear drive tyres)
• 4.10/3.50-4 (Wheelbarrows & utility carts)

Always clear away dirt or grass build-up to read the complete string, including the dash and final rim number, before ordering replacements.

Tyres, Inner Tubes, or Complete Wheel Assemblies?

Depending on condition, you can replace individual components or swap out the whole wheel assembly:

• Pneumatic Tyres & Tubes: If your rim is in good condition, browse our replacement tyres and inner tubes.
• Complete Rim & Wheel Sets: Replacing the entire wheel assembly saves fitting labor and solves problems with rusted or bent rims. View our pneumatic wheels and rims.
• Puncture-Proof Alternatives: Tired of flat tyres from bindi weed, thorns, or sharp debris? Switch to solid foam-filled puncture-proof wheels for zero maintenance.

Need Help Finding the Right Lawn Mower Tyre?

If your tyre markings are worn or illegible, note down your equipment make, model, and rim measurements, then contact the SWC support team in Auckland for technical assistance.

Browse our complete range of garden equipment tyres at SWC for delivery across New Zealand.