Tire Safety Tuesday / Speed Rating
Engine technology has come a long way in a short time. A new generation of powerplants, including smaller, high-output turbocharged engines, has not just improved fuel economy but has also significantly increased the performance potential of even the most basic family vehicle. As a result, tire manufacturers have had to drastically increase a tire’s speed rating – the designation that signals its maximum speed. That fact requires extra consumer vigilance when it comes to choosing replacement tires, says Falken Tire, a leader in ultra-high performance, light truck and all-season tires. Today, factory-specified tires for staid four-cylinder family sedans and even minivans often share speed ratings with those developed for ultra-high performance sports cars. With more horsepower on tap and subsequent higher speed capability, tires placed on the car by the vehicle maker must be capable of handling the car’s maximum speed. “High speed ratings—which indicate how fast a tire can roll at specified sustained speeds safely carrying a load--no longer are limited to the performance category,” explains Rick Brennan, Executive Director of Marketing at Falken Tire Corporation. “When replacing tires, consumers need to ensure that they’re not compromising safety by opting for a lower-speed rated tire. That warning is especially timely as cold-weather climate consumers are swapping out winter tires for all-season or summer tires. Winter tires generally have a lower (often “Q”) speed rating than the original tire speed rating (“B” to “Z”) specified by the car manufacturer. Consult the owner’s manual or the tire placard in the glove box or doorjamb for the correct tire size and speed rating for your vehicle. Changing fuel economy standards have been the prime reason more cars than ever now come equipped with high-speed rated tires. Emission regulations have fueled significant improvements in small engine performance, most notably for the popular, high-mileage, midsized family sedan category. Now, even small engine configurations are capable of high horsepower output – a trend that has significantly shifted tire engineering as well. “Today, it’s the rule rather than the exception for manufacturers to equip traditional family vehicles with super-efficient small displacement engines,” says Brennan. “With up to 200 horsepower, you’re as likely to see a 4-cylinder sedan as an 8-cylinder sports car equipped with high-speed rated tires, such as a V-speed rating (up to 149 mph).” While it may seem like overkill for a basic transportation vehicle to be optimized for these types of speeds, it’s a trend that’s here to stay, thanks to ongoing advancements in small engine technology, explains Brennan. For consumers preparing for a tire swap, Falken Tire offers the following recommendations:
Never downgrade. A tire’s speed rating indicates how fast a tire can roll while carrying a maximum load. Always select a replacement tire that at least matches the rating of the tires that were on the vehicle when it was purchased. You can go up – but never down.
Don’t rely on a tire’s speed rating to tell you how much grip or cornering ability the tire provides. The speed rating tells you how fast a tire can roll safely, not how much cornering capability it has. If you are looking for a tire that provides better handling or grip, you must research what the individual tire was designed to do. Consult the tire manufacturer’s website or ask the sales person at the tire dealer. For example, if you’re a driving enthusiast, look for replacement tires in the Ultra High Performance category: they are designed for sporty cars and more aggressive driving styles.
Never mix and match tires with different speed ratings. Doing so limits the speed you can drive your vehicle to the lowest rated tire on your car, which could be lower than the speed your car can reach. It can also expose you to potentially serious vehicle handling problems, including unpredictable steering.