What is it about your tire that lets your vehicle brake in time when a child darts onto the street, or swerve to miss a deer bolting from a bush? It’s the stability of your tire’s tread, the construction of the carcass, the compound of the rubber. It’s your tire speed rating, or, to be more accurate, your tire’s performance rating.
People refer to the last letter of the tire size on the sidewall of your tires as “ tire speed rating”-the maximum speed a tire can sustain for a certain period of time without the risk of tire failure. But it’s not just about speed. It’s about performance-how your tires get rid of heat and how they brake, corner, grip and swerve just in time.
In fact, your safety depends on the performance rating of your tires, and yet many drivers aren’t aware of the role they play in keeping their rubber on the road. As you get ready to switch to summer tires, and if you’re doing your research or shopping online, you need to know the tire size as well as the tire speed rating recommended by the vehicle manufacturer for your particular vehicle. One tire size could come in multiple speed ratings! You may find the exact brand and model at different Retailers and the prices are different. Rule of thumb is the lower the speed rating the lower the price and quality of tire.
Heat is your tire’s number one enemy. Tire with low speed ratings flex and squirm under pressure, causing heat build-up.
And heat build-up, along with high temperatures, can have a big impact on your tire’s performance and durability. You could be risking tire degradation, reduced traction and even blowouts.
Tires with higher performance ratings are better equipped to get rid of heat, in part because they generally have higher quality construction and ply.
Recent tests have shown upon hard braking in an emergency situation, a lower “S” rated tire driving at 100kmh took 39meters to stop where as a “V” rated tire took 35 meters .
Why? Performance rating has a huge impact on braking. Lower-rated tires will squirm and change shape under hard braking, taking longer to stop in emergency situations.
It isn’t the size but the quality construction of your tire that’s going to help you take sharp turns safely. If you’re heading up a highway ramp at high speeds and you’re not ready for the tight curve ahead, your vehicle will stay on the road, or not, because of your tire’s grip. Under force, the shape and contact patch of a lower rated-rated tire will change, reducing your traction.
As well, your vehicle operated safely because of several systems working in unison- anti-lock brakes, stability control, traction control- that can only work with the traction limits of your vehicle’s tires.
One of the biggest differences you’ll see and feel between tires with high and low performance ratings is the quickness of your steering response. You won’t have to turn your wheels as much when you have a tire with better traction because they can respond more accurately.
Less flex also improves stability, allowing your vehicle to swerve and remain steady on the road. Whatever you need to dodge or avoid in the roadway, you need lightning fast steering response.
It’s critical that your performance rating and load index matches the original equipment specifications recommended by the vehicle manufacturer. You can always go up in performance rating, but you can never downgrade or you’ll compromise the handling and safety of your vehicle. (The Exception to the rule is when it comes to winter tires.)
Note- You can find the Original tire size, Load and Speed Rating for your particular vehicle on the driver’s door jam or door opening.