Metzeler: 240/40R/18 = 25.8" tall Dunlop: 240/40R/18 = 25.91" tall Avon: 240/40R/18 = 25.5 " tall _________________________________ Dunlop: 250/40R/18 = 26.2 " tall Avon: 250/40R/18 = 25.8" tall Metzeler Does Not Make A 250/40R/18 Tire Hope this helps some
A 240 isnt always simply 240mm across. The shape of the tyre, the height and the way it sits on the rim will determine, especially when its mounted how wide it is.
Just remember as well, if youre comparing a mounted 240 on our rim, vs the standard 210 unmounted, depending on brand, it may not look all that different. In theory its only 30mm wider but when you take into account you've had to really cram it onto the rim, it can be less.
The way the sidewall sits and the shape of the tyre will also impact how it rubs / doesn't rub. Its just one of those things that when you're mounting a tyre that in reality, is too big for the wheel, it tends to highlight all the variations far more.