about mounting tires yourself is that you can do it properly. Most people don't realize that tires and wheels can not be made perfectly round. Manufacurers have agreed to make the low spot of the wheel at the valve stem, and the high spot of the tire will be marked with a dot. If you align the dot and the valve hole you get an almost perfectly round unit.
Properly aligned tire/wheel units last longer, run cooler and longer, and require less weight to balance.
