Ever wondered what all the information on your tyres means? When it comes to replacing your tyres, it may be useful to know what the differences are.
This is usually the company logo.
Manufacturers will tend to produce a number of different tyres for different applications.
3. Tyre fitting instruction
Tyres need to be mounted the correct way round on the wheel. Most tyres will have "OUTSIDE" clearly shown on the side wall meaning that this face points away from the car.
4. Tyre dimensions
This appears in the format: "Width/Aspect Structure Diameter". In the example above, '175' is the nominal cross section width in mm. The narrowest tyres for a smart are 135mm with the widest being 225mm.
The '55' is the ratio of side wall height to cross section width. When talking about low profile tyres, it is this figure which reduces.
The 'R' is the structure of the tyre. All smart tyres are Radial Ply.
The '15' is the diameter of the wheel (in inches) of which this tyre is intended to fit.
5. Tyre construction
Nearly all modern car tyres will be Radial allowing for slight fluctuations in tyre pressure so as not to affect handling. Other construction types include 'Bias' and 'Diagonal'.
6. Operational specification
In the example, the '77' is the load rating of the tyre. This figure corresponds to the mass (in kilograms) that the tyre can support. This will then give the speed rating of the tyre ('T' in this case). The higher the letter, the higher the maximum speed.
7. Inner Tube
No longer applicable on modern car tyres.
8. Direction of Rotation (Optional)
Tyres with 'handed' tread are only effective in one direction. It is important to observe this when refitting the wheels to ensure they are on the correct sides.
9. European ECE Type
This shows that the tyre meets all relevant EU IEC standards.
10. Country of Manufacture
Typically UK, France or Germany.
11. Additional operational specifactions
There may be extra details on what the tyre can cope with (weight / pressure).
12. Uniform Tyre Quality Grading
These figures for treadware, traction and temperature show how the tyre will fare against the recommended standard.
A treadware of '30' will last 30 times as long as the base standard.
A traction of 'A' indicates good traction. AA is the best, then A, B and finally C.
A temperature of 'A' indicates high resistance to heat. A is the best, then B and finally C.