Introduction

Ordering heavy-duty tyres online shouldn’t be guesswork. Every tyre has a “passport” engraved into its sidewall. This guide shows you exactly where to find the five pieces of information required by our JB4 Tyre Finder.

Step 1: Select Width (e.g. 315)

The first three digits on your tyre indicate its width in millimetres. This is measured from the widest point of the outer sidewall to the widest point of the inner sidewall.

• Where to look: It’s the very first number in the sequence.
• On the Finder: Match this number to the first dropdown to narrow your search immediately.

Step 2: Select Profile (e.g. 80)

The profile (or aspect ratio) is the height of the sidewall expressed as a percentage of the width. A “315/80” tyre means the height is 80% of its 315mm width.

• Where to look: It is always found immediately after the forward slash (/).
• On the Finder: Selecting the correct profile ensures the rolling circumference of your vehicle remains accurate for your tacho and speedo.

Step 3: Select Rim (e.g. 22.5)

The rim size is the diameter of the wheel flange in inches. For most heavy-duty UK trucks, this will be 22.5, but it can vary for smaller rigs or specialised trailers.

• Where to look: Look for the number following the letter ‘R‘ (which stands for Radial construction).
• On the Finder: This is a non-negotiable measurement; the tyre will not fit the wheel if this is incorrect.

Step 4: Select Brand

Once the dimensions are set, you can choose your manufacturer. At JB4, we stock everything from premium ‘Tier 1’ brands to high-quality budget alternatives.

• Where to look: The brand name (e.g., Michelin, Bridgestone, Continental) is usually the largest text on the tyre.
• On the Finder: Use this to filter by your preferred brand or leave it as “All Brands” to see every available option for your size.

Step 5: Select Pattern

The pattern refers to the specific tread design. This is vital because different patterns are built for different Axle Positions.

• Steer Axle: Usually features straight, vertical grooves for precision steering.
• Drive Axle: Features “chunky” tread blocks for maximum grip and power.
• Trailer Axle: Designed to resist side-scrubbing during tight turns.
• On the Finder: Choose the pattern that matches your vehicle’s current position or your specific operational needs (e.g., Long Haul vs. Regional).

A Note on Load & Speed Ratings

At the end of the size string, you will see a code like 156/150 L.

• Load Index (156/150): Ensures the tyre can carry your vehicle’s maximum weight.
• Speed Rating (L): The maximum safe speed for the tyre. Always ensure your new tyres meet or exceed the ratings of the tyres you are replacing.