The aspect ratio refers to the height of the cross-section of the tire to its width. This is a two-digit number that is usually slashed after the width of the tire. For example, you can say that the size of the tire is P215/65, which means its width is 215 and has a 65 aspect ratio. The 65 means that the tires aspect ratio is 65% of the width For example, "1501" indicates that the tire was manufactured during the 15th week of year 2001. This information is critical should there ever be evidence of a manufacturing problem and a tire recall. We encourage you to register your tires so that manufacturers can contact you in the case of a recall. Additional Tire Size and Capacity Information Is the ratio of the height of the tire's cross-section to its width. The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire's width. The bigger the aspect ratio, the bigger the tire's sidewall will be. The driver’s side door jamb. Inside your glove box compartment. Within your petrol tank hatch. Assuming your current tyres are the originally fitted, you can find tyre size data on the sidewall of your tyres. However, no matter where you find your tyre size, you will have to decipher a sequence of numbers and letters. Sport quads—20 to 25 inches. Utility quads—24 to 28 inches. Factory mud or rock equipped quads—27 to 30 inches. Keep in mind that you’ll want to keep within a couple inches of your stock tire size. If you go too big, you’ll start to rub on your fenders (among other issues). If you go small—well, that’s just silly. 55 refers to the profile of the tyre, or the distance between the wheel and the edge of the tyre, looking at it from the side. The number is the percentage of the width of the tyre. It is commonly known as the “aspect ratio”. So, the profile of our example tyre is 55% of 205mm, or 112.75mm. This number also increases in increments of 5. 4″ = refers to the diameter of the rim, in inches. It should be noted that tire sizes in the industry are not exact. It is not unusual for tire dimensions to be slightly different than the tire markings. For example, a 4.80/4.00-8″ tire typically has a 15.5″ diameter rather than the 16″ diameter you would expect. The RC tire width measurement is measured in millimetres starting at the point where the tires rubber meets the wheel so not including any other measurements such as RC tire offset or RC tire sidewall. There are many factors involved when measuring RC tires like offset, sidewall height, circumference etc. To measure RC car tires, keep in mind 3Pxi.