[Black Dog]

Almost any wheel can be made true to within a fraction of a mm if you don't care about even spoke tension. However, even spoke tension depends on the skill of the builder and the quality of the rim (more specially, how true the rim was before building). Some rims are easy to get very true and have even spoke tension while others are always going to force a compromise. Also some rims are "soft" and will bend easily from impacts and need to be re-trued and usually will require compromising even spoke tension to bring back to true. Since almost every single tire made has some runout, making a rim perfect in terms of vertical run out is less important than lateral trueness since the tire will still have tons of vertical runout. I would say that 1mm is max for vertical and about 0.5mm for lateral if it yields a wheel with very even spoke tension. A lot of good rims can be built to better tolerances than this and some bad ones will drive a builder crazy trying to get close to these numbers.