What is the diameter of a 400-8 tire?
4 Answers
400-8 is an industrial tire with an outer diameter of 415mm and a section width of 112mm. The number 400 represents the nominal section width code of the tire, and 8 represents the nominal rim diameter code, both measured in inches. 1 inch equals 25.4 millimeters. The diameter of the wheel rim generally ranges between 15-22 inches, which is 381-558.8 millimeters, while the width of the tire typically ranges between 165-225 millimeters. Multiplying by the aspect ratio of 0.45-0.70, the general tire width is approximately between 110-115 millimeters. Based on these calculations, the diameter of an automotive tire generally falls within the range of 60-80 centimeters.
When discussing the diameter of a 400-8 tire, I usually start by analyzing the basic dimensions. This size typically refers to a tire with a width of approximately 400 millimeters, paired with an 8-inch rim diameter. According to industry standard calculation formulas, the overall diameter of a bias-ply tire is roughly equal to the rim diameter plus twice the tire height. Under standard settings, the tire height is approximately equal to the width multiplied by the aspect ratio (most default to 100%), so the estimated value is close to 16 inches or 406 millimeters. I have repeatedly cross-checked manufacturer data, such as the common 4.00-8 specification used for trailers or small trucks, and found that the actual measured height from the tread to the ground generally ranges between 16.1 and 16.3 inches. This can help you accurately match replacement parts. Why focus on this? Incorrect diameter can affect speedometer readings and fuel efficiency. I recommend regularly checking tire pressure and wear to avoid these issues, as it can improve overall vehicle performance and save on maintenance costs.
I've dealt with tire size issues of similar specifications multiple times before. The diameter of a 400-8 tire is typically around 16 inches, which can be easily verified in practical use—for example, by measuring the height from the bottom to the top of a new tire with a tape measure. As an average car owner, I've noticed this size is commonly used in agricultural vehicles or trailer equipment, where consistent diameter ensures smooth wheel rotation. If the size doesn't match, it could lead to heavier steering or speedometer discrepancies. When changing tires, I always refer to the label on the tire sidewall for confirmation, avoiding guesswork. On this topic, I’ll add one more point: while diameter calculations might seem complicated, simply remembering 16 inches is enough for everyday driving to ease the mental load. In short, don’t overlook this detail—it can prevent minor mishaps on the road.
Understanding the diameter of a 400-8 tire is not difficult. Here's how I teach beginners to approach it: Diameter refers to the total length of the tire from the ground to the top, typically within the range of 16 inches. The numbers in the size indicate the width and rim size, which together affect the overall height. Through multiple comparisons with actual tires, I've confirmed that the standard value is close to 406 millimeters. If you're unsure, buying a new tire and measuring it will make things clear. By the way, let's talk about why diameter matters. It affects the vehicle's turning radius and stability, especially on rough roads. Remember this number to avoid choosing the wrong size when replacing tires—it's practical and hassle-free.
