What does ZR mean on a tyre?

ZR tyre rating explained

ZR signifies that the tyre rating complies with the requirements for sustained speeds that are greater than 149 mph (240 km/h). This rating has been used as a general high-speed designation as more detailed rating systems were developed.

Contemporary use

In modern usage, ZR is used with other specific letter ratings to indicate the precise maximum speed. For example:

• 225/40 ZR18 92W - meaning that the W indicates a limit of 168 mph
• 245/35 ZR19 93Y - meaning that the Y indicates a limit of 186 mph

The ZR prefix alone confirms that the tyre is designed for high-performance use. The subsequent letter after the load index gives the maximum speed attainable.