BARCODE said:Aside from being inflated for carrying loads, tires need to be round to work properly. Wheels also need to be round. However, due to manufacturing constraints, neither may be, exactly. So, wheel manufacturers tend to place the valve core hole (or some other mark) painted DOTS at the lowest point of the wheel. Tire manufacturers, on the other hand, tend to place a mark, usually a red dot, on the wheel's highest pint. The hope is if you put the higest point of the tire on the lowest point of the wheel, they will cancel out and you'll end up with a round wheel/tire combo.
Hope this helps..