Originally Posted by
Paul-JK
As far as I know the stated tyre width is the carcass width at the widest point of the tyre. I'd assume this this will usually be the side walls, although that could change slightly depending on width of the rims you've got them on and the tyre pressure. I'm guessing it will be measured at a "standard" pressure on "standard" rims but I've got no idea what those standards are. The tread width is always less than the stated tyre width but how much less depends on the tyre design. Can't help with muddies I'm affraid but for the 2 tyres that I've had the measurements were:
GY Wranglers; stated size 245/75/17; tread width 195mm
MT ATZ 4-Rib; stated size 285/70/17; tread width 240mm