Aspect Ratio

[Shordy]

Aspect ratio? What does that mean? I always thought that it was the depth of your side wall in millimetres? Anyone own a tape measure?

Just to answer your question, the aspect ratio refers to the way they measure tyres, example:
190/55-17 means 190mm wide, the height would be 55% of the width, and the rim diameter is 17", so the aspect ratio is 55% of 190mm.
Why they use a mixture of metric width and imperial wheel size has always intrigued me though.