Most people in Calgary worry about whether their tires will get them through the winter unscathed but many don’t know that the wrong speed rating can be just as hazardous as a slippery street.

A tire's speed rating is the last letter on the sidewall stamp and there are 14 possible ratings.

S is a common rating which equals 180 kilometers an hour, which is the top speed this tire can go.

Most buyers don’t pay attention to the letter and don’t realize the wrong one can increase the chances of having a crash.

“If you have the wrong tires on your car you could end up in a ditch or you could hit something or someone," said Mike Butcher, Kal Tire Senior Manager.

CTV Calgary Consumer Specialist Lea Williams-Doherty put the speed ratings to the test.

She found out that when you downgrade the speed rating on your tires you can create three specific hazards.

  1. A lower grade tire takes longer to stop
  2. The steering on downgraded tires is less responsive
  3. Downgraded tires produce more heat which increases your chance of a blowout

Lea went on a test drive and after running the course the S rated tires were six degrees hotter than the V rated tires.

Experts say the problem of accidental or intentional downgrading is growing because people are buying more tires online without guidance.

"I think a common mistake consumers make buying on line is they look at the tire size first and in most cases consumers are just looking for a less expensive tire,” said Butcher.

On the test cars, the lower rated S tire was only $25 cheaper than the V rated tire.

(With files from Lea Williams-Doherty)