Understanding Tyre Speed Rating and Load Index
Tyre speed rating is based on minimum standards for reaching and sustaining a specified speed. In general, a higher speed rating results in better car handling. There are two key warnings to be aware of when it comes to tyre speed rating.
It is both illegal and dangerous to drive with tyres that are lower than the recommended speed rating.
This can result in poor handling and unpredictable steering. There is no problem installing a higher speed rated tyre on your vehicle – this can improve cornering response.
It is not recommended that you mix and match tyres with different tyre speed ratings
Most tyre manufacturers recommend that speed-rated tyres be replaced in sets of four. If replaced in pairs, the new tyres should be of the same or higher speed rating. If tyres with different speed ratings are installed on a vehicle, it is recommended that they be installed with like pairs on the same axle.
It is highly recommended the lower speed-rated tyres be place on the front axle, regardless of which axle is the drive axle, to help prevent oversteer. (Oversteer occurs when the vehicle loses traction at the rear tyres first, causing the vehicle to spin and the driver to lose control.) The overall tyre speed rating for all tyres will become that of the lowest speed-rated tyre on the vehicle.
The chart shows a list of speed ratings along with the corresponding speeds they represent. Remember, the speeds are test speeds, not recommended speeds.
What is a tyre load rating?
The load capacity of a tyre determines what payload each tyre can carry. It is vital that you check with your manufacturer what capacity should be put on your car. Insurance can be void if you select the incorrect tyres. The tyre load rating table shows what index specification can carry.