What shoes should I wear? Everything you ever wanted to know about tires

If you are considering new tires for your Mustang, how will you know what size, construction and compound tire to go with? There are a lot of things to consider when selecting a tire for your Mustang, so let's look at a few.

To get started, we need to understand a few basics like how to read the “side wall” of a tire. Every tire has a number molded in the side wall such as P275/40ZR17, what do these numbers and letters mean? Here is a secret decoder ring:

• “P” - identifies the tire as a Passenger car tire (I am sure this is a relief to know)
• ”275” - defines the tire width in millimeters (for Americans divide by 24.9 to approximate inches)
• “40” - gives the aspect ratio (read on for a definition of this one, it’s the hard one to understand)
• “Z” – states the speed rating and ranges from B to ZR (of course, all Mustang owners NEED the ZR rating because this rating is good to 300 MPH!)
• “R” - specifies the tire construction (in this case Radial tire, no Alice, R doesn’t stand for “Race”!)
• “17”- tells us the wheel diameter this tire fits (defined in inches)


Ok, so most of these definitions are pretty straight forward. The only one that tends to be confusing is the Aspect ratio, (40) in our example. Aspect ratio is simply the ratio of the tire sidewall height to tire sidewall width. So if you compare a P275/40ZR17 tire to a P275/45ZR17 tire, even though both tires are the same width (275), the 45 series tire will have a taller side wall which means that the tire diameter will also be greater than the 40 series tire. If this tire had a 30 series aspect ratio, it would look to be a very skinny tire or very low profile.

Since we now know how tire sizes work, let's compare wear ratings, side wall stiffness and tread patterns. First, wear rating is fairly straight forward: the higher the wear rating number the longer the tire lasts under normal driving conditions. The tire with a higher wear rating is also a harder compound and requires less rolling resistance to roll the tire along the pavement. Since fuel economy is best with the least amount of rolling resistance, a harder tire provides the best fuel economy. The lowest wear rating is zero which means a very soft, very sticky tire that is probably intended for drag racing. This type of tire also has a soft side wall, which is good for drag racing but not very good for street driving or performance cornering. Tires with a low wear rating wear out very quickly because as the tire compound gets softer, more rubber is transferred to the pavement. So regardless of how many smoky burn outs are done as you leave the drive way, this type of tire wears out more quickly.

The second item to consider with tires is the side wall construction. Generally speaking the stiffer the side wall, the harsher the ride. For street driven cars you want a medium range side wall typically found on passenger cars. If you want to do more performance handling maneuvers, you need a stiffer side wall tire (usually matched with a softer compound or lower wear rating). If you want to hit the drag strip and maximize the grip, then a tire with a soft side wall and a low wear rating compound is desired.

Finally, let's consider tread patterns since they have a functional element and lately are making a styling statement to enhance your car's looks when it's sitting still. If you need to drive your car in all types of weather conditions, then you still can’t beat the “all weather” tread design. This design is not focused on providing good looks but is engineered to manage traction on dry or wet surfaces covered with/without water or snow. If your Mustang ride is focused street performance during dry surface conditions, then pick a tread design that both looks fast and makes a performance statement while standing still. As a hint, look at the correlation between how well a performance tire works and how much rubber is in contact with the pavement. Said another way, you typically want to minimize the “notches” in the tire for maximized grip.

So much for shopping for tires based "solely" on price! To pick the right shoes for your Mustang, you'll need to do a little bit of research and have a driving style in mind to ensure you come home with a choice that you makes happy for the life of your tire!

- Scott Hoag

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