The speed rating of a tyre is displayed on the sidewall. Like in the image, you will find it at the end of the tyre's size. It is always represented by a letter - in the following example the tyre speed rating is "V".
Once you know your tyre speed rating, you can work out what is the maximum speed your tyre is capable of maintaining.
For example, the "V" rating seen in the image, tells us that this tyre can reach speeds of up to 168mph.
Speed ratings are based on tests in which engineers run the tyre at 6.2 mph steps, in 10 minute increments, until the required speed has been met.
Effect on Car Insurance
It is very important that you check your speed & load rating before buying tyres. Choosing a tyre with a lower rating than is appropriate for your car can invalidate your insurance
The load rating (represented by the numerical value) is related to the maximum weight that tyre can carry. So in this case 105 would refer to a load capacity of 925kg, with most passenger vehicle load indexes range from 62 to 126.