Tyre size measurements

Hi all,

When a tyre is marked 100/80, what do those numbers relate to? I
understand they determine the width of the tyre, but at what points?

Thanks in advance,

Ben.

 

1st hit in Google was:
http://www.chris-longhurst.com/carbibles/index.html?menu.html&tyre_bible.html

"100" Section Width: The width of the tyre in millimetres from sidewall to
sidewall. This measurement varies depending on the width of the rim to which
the tyre is fitted: larger on a wider rim, smaller on a narrow rim. The
number on the side of tyre indicates the width measured with the tyre fitted
to the recommended rim width.
"80" Aspect Ratio: The ratio of height to width; this tyre's height is 65%
of its width.

PQ

 

Correction:

 

Thanks for that info PQ, now I understand. Great site too, lots of useful
info!

Cheers,

Ben.