Speed Rating (index)
- July 15, 2019
- Posted by: Admin_Drwilz
- Category: Principle
The speed rating indicates the maximum speed at which the tyre can be safely driven. Speed ratings range from N (87 mph) up to Y (186 mph). High-performance supercars such as Ferraris and McLarens sometimes have Z-rated tyres, although these are very specialist. These speed ratings exist to ensure the safety of your tyres.
At higher speeds, the wheels turn faster and more heat is generated. So, it’s important that the chosen tyre can cope with this extra heat, and running a tyre with too low a speed rating for the car risks the failure of the tyre at high speeds.
A tyre’s speed rating is the top speed it can maintain under its approved load capacity. For example, a tyre with a speed rating of ‘Y’ has a top speed of 186 mph.
Your tyre’s speed rating can be found in the tyre’s sidewall data and is always referenced in the form of a letter, usually after the wheel diameter. In the image below you can see the tyre has a diameter of 16 inches, a load rating of 87 and a speed rating of ‘V’.
For most modern cars, the tyre rating doesn’t reflect the actual speed that the vehicle is capable of. Most family cars will have a tyre speed rating that is much higher than the car’s maximum speed. For example, smaller city cars tend to have a T rating (118 mph); most common on family cars are H-rated (130 mph) and V-rated (149 mph) tyres.
Partly this is due to current fashion, as the trend for alloy wheels with low-profile tyres means that manufacturers tend to choose tyres for their aesthetics, so higher performance tyres are fitted. But partly this is due to safety, to ensure that the performance of the tyres always exceeds the performance of the car. A higher speed rating ensures that the tyre is able to cope with the loads imposed by acceleration, braking and high-speed cornering.
Speed ratings are measured from the results of tests carried out by engineers in 6.2 mph steps, at 10-minute increments until the desired speed has been met.
The table below displays a tyre’s maximum speed and its rating: