Tires, why do they have a speed rating? If the rating is a V, why cant you put on a tire that has an S rating?

Question

Tires come in all sorts of speed ratings, Q,S, T, H, V, W, and Z. Why is it so important to be sure you replace the tire with the same speed rating? Most people dont even know that there is a difference.

Answer 1

First, to correct the earlier comment, V is not for "Vans," or T for "Trucks," etc. V is a tire that is speed rated for upto 149MPH. S is for a tire rated to 112MPH. T is for tires rated upto 118MPH. P is a tire rated for 93MPH.

Speed ratings on tires generally developed for European use, where highways speed limits are often higher, and sometimes unlimited. European governments mandated that cars must have tires appropriate to the maximum speed the car is capable of (which is also why you see many German cars with electronic speed limiters, which keeps the manufacturer from having to install more expensive tires).

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). 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.

You don't have to replace your tire with one that has the same speed rating, though chances are the tire your car came with is a good reflection of what is the minimum tire in terms of appropriate performance, so you normally don't want to put a lesser tire on (and as the tire is the one part element that actually touches the ground, and is the limiting factor in EVERYTHING your car does, why would you want to go for something less int his one very important area).

Answer 2

There are 3 main parameters that determine the speed rating. One is the hardness of the tread. The softer rubber in higher speed rated tires grips the irregular surface of the road better and is less likely to skid at high speed. The lower speed rated tires have a harder tread that is more durable. Second the belting of high-speed tires is stronger in order to handle the stronger forces impose by high-speed manuevers. Third.. High speed rated tires are designed to handle the higher temperatures created by braking and acceleration of a performance car.
Insurance companies prohibit tire shops from replacing tires with lower speed rated tires, to help limit the legal liability of the tire shop being sued when someone skids out his 'vette on S-rated tires and smashes the pretty plastic against a tree.
Also the suspension of the car is deisgned to work with certain characteristics of the tire, so a lower speed rating will definitely influence the handling of the car.

Answer 3

For normal city usage and smaller capacity cars, the normal range of tire is enough to do the job. However, for high performance cars, a higher peed rating is needed, as these cars can easily moving at more than 100 mph
It is always to put on a tire with the higher rating but not the reserve! as safety is compromised.
The higher the rating the costier the tire for the ability to meet high speed requirements and additional safety measures.
More people is concerned with cost when time to replace tires and fail to ask enough questions

Answer 4

I heard it ever since I started in the tire business. Why can't I put an S-rated tire on my Z-rated car I never drive that fast. Listen, most customers want the cheapest tires on their vehicles its human nature to save money. Listen, the engineers designed your vehicle with the tires plus their rating as part of the whole package. So don't second guess them...OK. Just buy the cheapest in the proper category...

Answer 5

A tire with a S rating is one that has been tested up to a certain speed or S. One with the letter V means for Vans. The letter T is for Trucks. One with the letter P is for Passenger Car. And if it has the letter R..it means it is a radial tire. Hope this clears up your question concerning tires. For more info visit your local tire shop, they will be glad to answer your questions concerning tires.

Answer 6

Because it keeps the people who don't have a clue out of potential trouble.