Help with tyre size meanings

[aesmith]

Hi,

I'm familiar with the size markings for road tyres. For example our Landrover has 235/85 16 (omitting load, construction and speed rating). Meaning 235mm wide, height is 85% of width, and 16" rim diameter. If omitted, aspect ratio is 80%.

Tractor tyres seem to have either fewer or more measurements. For example 7-16 is presumably 7" wide on 16" rim. Height is what, 80% of the width like a road tyre, or something else?

Turf and some industrial have more sizing figures, for example 27 x 8.5-15. I can guess that's 15" rim diameter utility what does the 27 indicate?

See a couple of examples of agriculture and equipment turf or industrial tyres ..

 

[TractorTech]

The 27 indicates that it is 27" in diameter.

 

[aesmith]

Cheers. Can I ask how to get diameter from the other formats, for example 11.2-24?

Trying to square my workings with fact that one example quotes around 10% slower on 15-19.5 compared to 11.2-24.