How do you measure wheels, I mean ? OK.. The wheels on my mower are shot , bearings and all, so I want to get new ones.. So I measure them and they are 7 1/2" high, so I go looking for new ones, they all are listed at 8" ?? Is that right , WOuld the 8 " wheel be OK to use or does that 8" wheel actually measure 7.5" ?? and does anyone know if the wheel s on a bobcat version are the same ?? cause those are the only ones I have found ?? Thanks..