In tires, aspect ratio refers to the ratio of the height of the tire's sidewall to its width.

• A. The tread depth
• B. The wheel diameter
• C. The ratio of the sidewall height to width
• D. The tire load index

Answer: (C)

Understanding aspect ratio starts with the relationship between sidewall height and tire width. Aspect ratio is the sidewall height expressed as a percentage of the tire width. For example, a 205/55 tire has a sidewall height that is 55% of 205 mm, about 113 mm. This ratio affects ride comfort and handling: higher aspect ratios give more cushioning, while lower ratios result in a stiffer ride and crisper steering.

Other tire attributes are separate: tread depth relates to how far the tread grooves extend, wheel diameter is the size of the wheel the tire fits, and the load index indicates the maximum load the tire can carry. The statement that aspect ratio is the ratio of sidewall height to width is the correct description.