Tires are likely the most overlooked item on any hot rod. The problem is that they also have one of the biggest effects on a car’s performance. Most any average ride can vault to fast-car status by just tossing on some super-sticky race rubber. Even a car with a great suspension can be hobbled by hard tires that grip slightly better than butter. That’s why it’s important to put as much thought into choosing tires as you do on the more glamorous go-fast goodies. And while at first glance it may seem like tires are fairly straightforward, the truth is there’s a ton of science packed into every grooved ring of rubber. It may seem cool to run 40 treadwear autocross race slicks on your daily driver, but they will wear out quickly and heat cycle into hard and gripless junk before you know it.
Show up to a speed-driving event on tires with too low a speed rating and you’ll end up a spectator instead of a driver.
Yep, shopping for tires is serious business, and to make the right choices you’ll need a little knowledge. Now, we could fill this book from cover to cover with tire info and still have more to say, so this time around we’ll just touch on the basics so you’ll know the terminology and what all that info stamped on the sidewall of every tire actually means. After all, knowledge is power, and who doesn’t want more power?
Tread design combines a little art with a ton of science, as each tire manufacturer has their own ideas on what works best for a given driving segment.
The most common pattern is called symmetric. Symmetrical tires have the same pattern on both the inboard and outboard halves and it doesn’t care which direction it rotates. It makes rotating your tires easy, but they come up short in the performance department. In other words, they are great for your family sedan—not so hot for your Pro Touring Camaro.
Next up are tires with an asymmetric pattern. These combine great water dispersion with excellent dry grip since the designers can vary the tread pattern across the face of the tire. Usually they incorporate larger tread blocks on the outboard side for increased cornering stability on dry roads (which also reduces tread squirm and heat buildup on the outside shoulder). The inboard typically has smaller independent tread blocks for improved wet traction. A dead giveaway on these tires is that they will be stamped “INSIDE” on one side of the tire and “OUTSIDE” on the other.
Directional pattern tires (also referred to as unidirectional) incorporate lateral grooves on both sides of the tire’s centerline that run in the same direction and create V- or wedge-shaped tread blocks. This really helps in the rain as the pattern “pumps” water more efficiently out from under the tire. These tires are designed to only spin in one direction and will be marked “LEFT” on one side of the tire and “RIGHT” on the other, or with directional arrows.
Lastly, there are asymmetric and directional patterned tires that combine the previous two designs. They're treated as directional in terms of rotation, and if you run different sized tires front and rear then each tire becomes location-specific and negates the possibility of rotating your tires.
What pattern works best? Post on any Internet message board and you’ll be deluged by “keyboard warriors” trying to push their point of view. If you plan on road racing, autocrossing, or carving up the nearest mountain road, then find out what others are running in the real world.
Now, let’s figure out what all the other data stamped into the side of your tire actually means.
|Traction Grades||Asphalt g force||Concrete g force|
|C||Less than 0.38||0.26|
|Temperature Grade||Speeds (in mph)|
|B||100 to 115|
|C||85 to 100|
Trivia: a typical valve stem weighs about 1.2 ounces more than the aluminum that was bored out to make room for it.