A tyre size code such as 205/55 R16 91V gives six facts in order: width in millimetres (205), sidewall height as a percentage of width (55), radial construction (R), rim diameter in inches (16), load index (91) and speed rating (V). Read left to right, it tells you which tyres fit your wheel and what they can carry.
Updated November 2026
Tyre size 205/55 R16 91V decoded
| Part of the code | Example | What it tells you |
|---|---|---|
| Width | 205 | Tyre width in millimetres, sidewall to sidewall |
| Aspect ratio | 55 | Sidewall height is 55% of the width |
| Construction | R | Radial, the standard build for cars |
| Rim diameter | 16 | Fits a 16-inch wheel |
| Load index | 91 | Carries up to 615 kg per tyre |
| Speed rating | V | Rated up to 240 km/h (149 mph) |
Source: Goodyear and Michelin.
Where do you find the tyre size?
The tyre size is moulded into the sidewall of every tyre, in the format above. Your owner’s handbook lists the sizes the manufacturer approved for your car, and many cars also carry a sticker on the driver’s door frame. Check the handbook before you change size.
What does the width and aspect ratio mean?
The first number is width in millimetres and the second is the aspect ratio. Together they set how tall the sidewall is. A 205/55 tyre has a sidewall 55% of 205 mm high, about 113 mm. A lower ratio, such as 40, means a shorter, stiffer sidewall. A higher ratio, such as 65, means a taller, softer one.
What does R16 mean?
The letter is the construction and the number is the rim diameter in inches. R stands for radial. The 16 must match your wheel exactly, because a 16-inch tyre only seats on a 16-inch rim.
What is the load index?
The load index is a number that maps to the maximum weight one tyre can carry. It is not a weight itself. A sample from the Michelin chart:
| Load index | Max load per tyre |
|---|---|
| 87 | 545 kg |
| 91 | 615 kg |
| 95 | 690 kg |
| 99 | 775 kg |
| 103 | 875 kg |
Source: Michelin load index chart.
Higher is fine, lower is not. A tyre with a higher load index than the original can be fitted if the handbook allows it. A lower index means the tyre may be overloaded, so it should not be used.
What is the speed rating?
The speed rating is a letter showing the top speed the tyre is designed to carry at its maximum load. Common symbols:
| Symbol | Max speed |
|---|---|
| Q | 160 km/h (99 mph) |
| S | 180 km/h (112 mph) |
| T | 190 km/h (118 mph) |
| H | 210 km/h (130 mph) |
| V | 240 km/h (149 mph) |
| W | 270 km/h (168 mph) |
| Y | 300 km/h (186 mph) |
Source: Michelin speed rating chart.
The rating is not a speed target. UK limits are far lower. It is a measure of heat and strength margin, so match or exceed what your car’s manufacturer specifies. Goodyear notes that a lower speed rating is sometimes acceptable on winter or all-season tyres, but only under conditions set out in its guidance, so ask before you assume.
What other markings sit on the sidewall?
Four further markings are common.
- DOT code: a four-digit date stamp showing the week and year of manufacture. Our guide to tyre age and the DOT code explains how to read it.
- XL or Extra Load: a reinforced tyre with a higher load capacity than a standard tyre of the same size.
- Three-peak mountain snowflake: a symbol showing the tyre meets a winter performance standard. Our winter versus all-season guide covers the choice.
- Run-flat markings: see run-flat tyres before you mix types.
What is the legal minimum tread?
For most cars, the legal minimum tread depth is 1.6 mm across the central three-quarters of the tread, around the whole circumference, per the DVSA MOT inspection manual.
Same size, different tyre
Two tyres can share a size and still differ in load index, speed rating, rubber compound and price. Size makes a tyre fit. The load and speed figures make it suitable. If you are choosing, start from the full code on your current tyre, then see the tyres we fit in Manchester.
FAQ
Can I fit a different tyre size to my car?
Only if the manufacturer allows it. Check your handbook, and ask a fitter before you change width, ratio or rim size.
Is a higher speed rating always better?
Not necessarily. It must meet or exceed what your car needs. Higher ratings can bring a stiffer ride and cost more.
Where is the tyre size on my car?
On the tyre sidewall. The handbook and the driver’s door sticker, if fitted, list approved sizes.
What are your opening hours?
Monday to Friday 9:00 to 17:30, Saturday 9:00 to 16:30, closed on Sunday.
About Hyde Road Wheels & Tyres
Hyde Road Wheels & Tyres Ltd is a family-owned tyre shop and DVSA MOT test station at 270 Hyde Road, Gorton, Manchester M12 5FH, in business since 1987.
Not sure what your sidewall says? Call 0161 274 3125 or use the contact form. We are at 270 Hyde Road, Gorton, Manchester M12 5FH, open Monday to Friday 9:00 to 17:30 and Saturday 9:00 to 16:30. Closed Sunday.
Need tyres, an MOT or a repair in Gorton?
Ring the garage on 0161 274 3125 or come to 270 Hyde Road. We will tell you what the car needs before any work starts.