Understanding Tire speed ratings

April 29, 2010 - PRLog -- Speed Rating

In Germany some highways do not have speed limits and high speed driving is permitted. Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments). Despite the tire manufacturer's ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.

Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating, even after being repaired because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:





A tire receives its speed rating by the U.S. Government through meeting minimum standards for reaching and sustaining a specified speed. What does that mean to you? Well, in general, a higher speed rating will result in better car handling.
Two important notes when considering speed rating:
• We do not recommend downgrading the speed rating of your tires. This may result in poor handling and unpredictable steering. However, if you want better cornering response, there is no problem installing a higher speed rated tire on your vehicle.

• Never mix and match tires with different speed ratings on your vehicle. This will cause serious problems with the handling of your vehicle.

Below is a list of speed ratings along with the corresponding speeds they represent. Remember, the speeds are test speeds, not recommended speeds.


 
Q- Up to 100mph
R- Up to 106mph
S- Up to 112mph
T- Up to 118mph  U- Up to 124mph
H- Up to 130mph
V- Up to 149mph  W- Up to 168mph
Y- Up to 186mph
Z- 149mph and over

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