[Fast Freddie]

Aspect ratio: The ratio of the tire sidewall height (the distance from tread to rim) to its overall width. The ratio number is usually used with the expression ?series?. The lower the number, the lower the tire profile, this means that a 50-series tire has a lower profile than a 60-series tire. In most cases, a shorter sidewall height (lower series number) creates a more responsive tire, but it is less capable of isolating road noise and surface disturbances.

 

[clavos]

I'll just delve a bit deeper on the aspect ratio in that the series represents a percentage of the tread width. For example, a 225/40/18 tire size would translate as this. The 225 equals the width of the tread in mm. The 40 equals 40 percent of the tread width or 90mm in this case, and is the distance from the rim to the tread. Last but not least, we all know the 18 is the diameter of the rim.

 

[Fast Freddie]

great info clavos

 

[DrJones]

The old tire standard was better.

I had 35/12.50/R15s on my truck. 35 inches high, 12 and a half inches wide, 15 inch wheel. Makes much more sense (and involves less math) than the new standard.