Low profile tires are becoming more popular, so upgrading to a larger wheel can be a great way to improve the appearance of your car. You can also increase performance by having a shorter sidewall. This allows for more grip and lateral stability. A larger wheel will allow you to choose from a wider range of compatible tires, especially for performance models.

There are tradeoffs. Tires are heavier than wheels so the weight of tires goes up with wheel size. This can negatively impact fuel economy, acceleration, and make the steering heavier. A shorter sidewall provides less cushion and makes the car ride harder.

HOW BIG CAN I GO?

The tires and wheels may rub against the fender when turning tight or when the suspension bottoms. Speedometers measure speed by measuring the distance traveled for each wheel turn. A size change could cause the reading to be inaccurate. Both the stock width and the tire width must be maintained in order to keep the suspension and speedometer working properly.

It is safe to fit a tire that is up to 20 millimeters larger than the stock rim. The width of your rim will affect the tire’s actual width. For every inch (12.5 millimeters), that is added to the rim width, the tire will expand by 5 millimeters.

It can be a bit more difficult to move to a different wheel because the tire sizes are both metric and percentage. Wheel sizes, however, are in Imperial measurements.

For example, the car currently has 225/45R15 tires. Here’s what that means:

• 225 – Tire width measured in millimeters
• 45 – Sidewall height in relation to tire width
• 15 – Rim diameter measured in inches

To convert the wheel size into millimeters, multiply by 25.4:

• 15 inches x 25.4 = 381 millimeters

Next, calculate the sidewall height by multiplying the tire width by the height percentage:

• 225 millimeters x 0.45 = 101.25 millimeters

Add the two numbers together, to get the total height of the wheel and tire:

• 381 + 101.25 = 482.25 millimeters

The new tire and wheel should not exceed 3 percent of the original combination’s combined height to keep speedometer errors in check. To fit a 16-inch (406.4 millimeters wide) rim, a tire should have a height of 75.85 mm, which is 34 percent of 220 millimeters, or 220/34R16. Closest size is 220/30R16. This is within the 3 percent margin.