Power is the dessert of car modifications; it gets all the attention. It should be done last, but everyone wants to do it first. Tires are the vegetables. They are no one’s favorite, but they are easily the most important.
I have seen people double the power output of a car and not upgrade the stock, all-season tires. This is a recipe for disaster. It’s the same way with a perfect suspension or giant brakes. Every modification made to a car can be enhanced or crippled by tire choice. A proper set of tires is the easiest way to enhance the performance of a car.
First, you need to decide what size tire you need. This is determined by the size of your wheel. Tires are sized using three numbers: section width in millimeters, sidewall height as a ratio of the section width, and the rim size in inches. Tread width is the actual contact area of the tire and is narrower than the section width. The section width can vary with manufacturer; one company’s 225 may be another’s 215 or 235. The sidewall size and rim diameter determine the tire’s height; this is important for the accuracy of the speedometer, odometer and traction control.
Luckily, Tire Rack has mounted and measured every tire they sell. They will list what size wheel they measured the tire on, the section width, the tread width, and the suggested rim width. Anywhere in their suggested range will work. A narrower wheel will provide more protection from curb rash, and a wider wheel will provide better steering feel.
For a 225/45r17, the tread is 225 mm wide, the side wall is 45% of 225 mm, and the rim height is 17 inches. With a measuring rim of 7.5 inches, the section width is 8.9 inches, and the suggested rim width is 7-8.5 inches.
Where will the car be driven? This will decide what category of tire you should be shopping in. There are four main categories:
- Summer: Good year-round in the South; Summer-only in the North
- All-Season: Good year-round in all but the most northern parts of the US
- Winter: Good during the winter, especially in places with heavy snow
- Track: Only for race tracks and very limited street use (R-compound)
|Dry Performance||Wet Performance||Snow Performance|
What do you need the tire to do? Once you pick your category, there are several sub-categories dividing tire styles by performance and features. In the summer and all-season tire categories, they are further divided by performance level; some overlap can occur here as a ultra high performance all-season tire may outperform a grand touring summer tire. Track and winter tires are divided by features (dry vs wet race tires or studded vs non-studded snow tires).
Treadwear, like section width, is another vague tire measurement. The trend is lower numbers offer more grip with a shorter life span. This number is derived from a test where the tire is driven on until worn and the distance traveled determines the given treadwear. Despite this, two different 200 treadwear tires could last different distances and offer different levels of grip. Really, this is a general guideline, not a rule.
Speed rating is usually irrelevant as long as you choose from the proper category for your intended needs. The all-season tires for your daily should be good to 120-130 mph; while, the high performance summer tires on your sports car should be good to at least 150 mph. Load rating is another measurement that is irrelevant as the tires can usually support far more than the car would ever weigh.
Picking a Tire
If your plan is to increase handling and performance, really your only option is a summer tire. Don’t just pick the widest tire you can fit on the wheel; look up the size of your wheel and pick a properly sized tire. People usually want to cheap out on their tires as they will just wear out; but a good name brand tire usually performs better while lasting longer. However, some of the newer tire brands are making great progress, and a name brand can put out a sub-par product. Do your research; reviews by regular people can be far more insightful than the nonsense numbers on the side of the tire. Picking the right tire is the most impactful performance modification you can make.
I have a 2003 Nissan 350Z that I drive everyday in the southern half the United States. The stock tire size for the 19X8.5 inch wheel is 245/35r19. I chose a max performance summer tire: Continental Extreme Contact DW. The measuring rim was 8.5 inches giving an 8.3 inch tread width and a 9.3 inch section width. The treadwear is 340 which is higher than the older Sport Contact 5 at 220 (meaning it will likely last longer), but the new tire manages to offer better grip (based on consumer reviews). The load rating is way higher than I would ever need, and the speed rating is faster than my car can go.
I don’t use those wheels at the track; I have a second set of wheels with lightly used race tires on them. If you have the means, a second set of wheels is a great way to widen the range of your tires. On the street, I use my pricey but durable summer tires but on the track, I use my cheap and ultra-sticky used race slicks. If you deal with heavy snow in the winter, a set of wheels with snow tires and a set with summer tires would allow optimum performance all year long.
I know it’s hard to spend hundreds, even thousands of dollars on a part that may only last you a few years, but without a good tire, all your other modifications are basically worthless. The key to the best driving experience: proper tires.