How To Read Tyre Numbers: The Complete Guide

That string of numbers on your tyre sidewall — something like 205/55 R16 91V M+S — might look like a random code, but every character carries important information about what the tyre can and cannot do safely. This guide explains all of it.

The basic size code (e.g. 205/55 R16)

The first three digits are the section width in millimetres — how wide the tyre is. The two digits after the slash are the aspect ratio — the sidewall height as a percentage of the width. R indicates radial construction. The final two digits are the rim diameter in inches.

So 205/55 R16 is: 205mm wide, sidewall height = 55% of 205 = 112.75mm, radial construction, fits a 16-inch wheel.

Load index

The two or three digit number after the rim size (e.g. 91) is the load index — the maximum weight each tyre can carry at full inflation. 91 = 615 kg per tyre. Never fit a tyre with a lower index than the manufacturer specifies.

Speed rating

The letter after the load index (e.g. V) indicates the maximum sustained speed: T = 190 km/h, H = 210, V = 240, W = 270, Y = 300. Always match or exceed your original rating.

Additional markings

• M+S or M&S — Mud + Snow. Minimum winter capability, but not the same as a true winter tyre.
• Three-peak mountain snowflake (3PMSF) — genuine winter-rated tyre, tested on snow. Far more capable than M+S alone.
• Run Flat / RFT / SSR / EMT — the tyre can be driven on for a limited distance (typically 80km at 80km/h) after a puncture.
• XL or Extra Load — reinforced sidewall, can carry more weight. Often required on heavier cars and SUVs.
• MO / AO / HO / JLR — manufacturer Original Equipment markings (Mercedes, Audi, Honda, Jaguar Land Rover). These tyres are tuned for specific vehicles and should ideally be replaced like-for-like.
• DOT followed by 4 digits — the manufacturing date. The last 4 digits are the week and year (e.g. 2319 = week 23 of 2019). Tyres over 10 years old should be replaced even with tread remaining, as the rubber hardens and cracks.

EU tyre label

Since 2021 all new tyres sold in the UK must carry a label showing fuel efficiency (A-E), wet grip (A-E) and external rolling noise in decibels. Higher ratings in the first two categories mean better performance. A wet grip rating of A stops noticeably shorter in the rain than a C-rated tyre — something worth paying attention to on North Wales roads.

If you’re not sure which tyre is right for your vehicle, WhatsApp us a photo of your current tyre sidewall and we’ll recommend the best match for your budget.