October 24, 2012 – The day that speed demons everywhere cried with joy. The day that Chrysler Inc. decided to pursue the concept of the powerful Hellcat (that may not be true). The day that Texas announced their 85-mph speed limit on Hwy 130.
Possibly the day that hundreds of car-enthusiasts decided to upgrade their tires.
“Tires?? Why would they buy new tires??”, you ask.
Good question. The answer? The tire’s speed rating.
Speed rating is what kind of miles per hour a tire is capable of withstanding. Think of it in the sense of the term, “burning rubber.” When a tire meets the road, it does so continuously, over and over again as it carries your vehicle across a stretch of distance. This creates friction, thus heat. The faster you go, the more the tire meets the road, the more friction, the more heat. Alas, the term “burning rubber.”
Found in the alphanumeric “service description” next to a tire’s size on the sidewall, speed rating is assessed from a lab test by the manufacturer where the tire is applied to a large metal drum at the pressure that equates to the load rating. The tire is spun against the drum at increasing speeds in ten minute intervals until the necessary speed limit is met. That number is represented by a letter.
It should be noted that these gradings assume the tire has not been damaged, is within tread life, is properly inflated, and that routine maintenance (ie: rotation) has been kept up.
Now before you start hyperventilating that you need a “Z”-rated tire on your minivan, keep in mind that most cars have a “top” speed they can reach before they max out. It would be kind of worthless to equip your Sienna with Z(Y) tires when the fastest it can reach is 120 mph. (Which makes it the perfect vehicle for your driver-in-training teenager, right?) Save your money for that freedom cruise when the kid finally turns 18 – for you, not them. Conversely, it’s not a good idea to put a lower-rated tire on a higher-rated vehicle. This is why it’s suggested you only ride on the spare tire for a day or two at lower speeds – it really can’t handle much more than that.
Of course, if you are, hypothetically, one of these mythical speed demons (because no one ever really tests out the reaches of their muscle engine, surely), then some crazies in the tire industry brought us the “Z-series.” As you can see in the infographic, Z-rated tires are then expanded into three levels. These tires have the best grip and stopping power, but when (hypothetically) used to their purpose, have a very weak tread life. Yes, these are the tires the Nascar drivers have to change every twelve left turns – because they’ve quite literally burned off the tread. (Whoa.)
Ever seen those shredded tires on the interstate left in the wake of an 18-wheeler? That’s the fate of a tire not properly rated to the weight and speed of it’s automobile. For a semi, it has a multitude of back-ups. For you, the results could be fatal. A safe rule of thumb is to stay with the speed rating chosen by your vehicle’s manufacturer, or, as always, consult an expert.
There you have it. The last of our four primary components that define the perfect tire for your ride. We’ve smoothed out the points of ride quality, lengthened the life of your tire, bundled you up for inclement weather tires, and, finally, given you a quick recap of speed rating. Hopefully these basics will help you in your next tire-search. Of course, these are still only a small slice of the pie that is complicated tire formulas, but maybe now the words our tire experts are saying will make a little more sense – saving you time in your next visit.
This post, including graphics, was created by Milton Ruben Social Media Specialist, Heather Cortright.