Tire speed rating indicates the maximum speed at which the tires should be run in continuous operation.
Ratings you’re likely to see the next time you go to buy tires: S (112mph), T (118mph), U (124mph), H (130mph), V (149mph), and Z (or ZR) (above 149mph). Ratings H, V, and Z (or ZR) are most common for street tires, and often the same size and model of tire is available in two, or all three, of these ratings.
Always select tires having the same or higher speed rating as those recommended by the bike’s manufacturer.
Keep in mind, though, that the faster-rated tire won’t make your bike faster. Paying extra for a Z-rated tire on a bike that tops out at 110mph is a waste.