What tire is used on a 24 X 3 wheel and also a 25 X 2 12 wheel. Both had 30 X 3 on them. Is that correct?
The 24inch is the dia of the wheel and the 3 is the height, so 24+3+3=30 inches (total height)
The same for the 25 inch wheel 25+2.5+2.5=30 inches.
It would seem that 30x3 could fit both rims but the overall height (and circumference) will differ from the original. Hope that makes sense.
A 30X3 does indeed properly fit a 24 inch rim, and may be able to be stretched onto a 25 inch rim, but will not really fit.
Are these wheels both on the same car? Are they truly different? A 25X2.5 is not a common size wheel, at least not in the USA. It would require a 30X2.5 or a 31X3 to fit properly.
Tire sizes can be very confusing because they are sometimes measured inside-out, and other times they are measured outside-in. Andrew H shows the math for them.
Drive carefully, and enjoy, W2