How to Read Your Tyre Size and Date Code

Learn what the numbers on your tyre sidewall mean, how to find the tyre's age, and why old tyres can be dangerous even with good tread.

RCJ Mobile Mechanics

10/12/20262 min read

four vehicle tires
four vehicle tires

The writing on the side of your tyre tells you almost everything you need to know about it, including whether it's the right size and how old it really is.

Reading the tyre size

Take a common size like 195/65R15 91H:

  • 195 is the tyre's width in millimetres.

  • 65 is the aspect ratio: the sidewall height is 65 percent of the width.

  • R means radial construction, which almost all car tyres are.

  • 15 is the wheel diameter in inches.

  • 91 is the load index: how much weight each tyre can safely carry.

  • H is the speed rating: the maximum speed the tyre is built for.

When replacing tyres, stick to the size and load rating recommended for your vehicle. You'll usually find it on a sticker inside the driver's door frame or in the owner's manual.

Finding the tyre's age

Look for the letters DOT followed by a series of characters. The last four digits are the date code.

For example, 2321 means the tyre was made in the 23rd week of 2021.

Why tyre age matters

Rubber ages even when the tyre isn't being used. Heat and sunlight speed this up, and Jamaica has plenty of both. Old tyres can develop cracks in the sidewall and between the tread blocks, lose grip and become more likely to fail.

Many tyre manufacturers recommend inspecting tyres closely once they reach around five years old and replacing them by around ten years old, regardless of tread depth. Some imported used tyres are already several years old when fitted, so always check the date code before you buy.

Checking tread depth

Most tyres have small raised bars called tread wear indicators in the grooves. When the tread is worn down level with these bars, the tyre needs replacing. Worn tyres are especially dangerous on wet roads during the rainy season.

Other things to look for

  • Bulges or bubbles in the sidewall (replace immediately)

  • Cuts and cracks

  • Uneven wear, which can point to alignment or suspension problems

  • Nails or screws in the tread

Need help with this? RCJ Mobile Mechanics comes to you in Portmore, Spanish Town, Kingston, St. Andrew and across St. Catherine. Call or WhatsApp (658) 207-6565 or book a mechanic online.