Acceptable Trueness Tolerances for New Wheels?
 

What are reasonable errors (metric) for lateral and radial truenesses on a new wheel build, assuming excellent rim quality?

I have seen 0.5 mm mentioned several times for roundness and lateral run-out.

the way they build rims nowadays, you might see a little more than .5mm vertical runout on a properly trued wheel. I usually try to get a circular brake track if that's the case. Side to side should be less than that, definitely.

Would It matter if it were rim brake v. disc brake? Trueness matters all the way around, but would the tolerances change for different applications?

I give some rims more tolerance for vertical lateral true in order to have more even tension. Not every rim can be built up to ±0.2mm and still have the spokes tensioned evenly. If you look at Shimano's instructions for brake pad/rim clearance they recommend 1.5-2.0mm on each side. A rim that's ±0.5mm won't be an issue.

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.

It matters to the builder if she/he cares but, yes, less so for disk wheels. Perfectly even spoke tension is key to long lived wheel that will stay true through a trip through hell and back.

Agreed.

Regarding wheels building better when supplied with quality rims: I built a set of the new Open Pro rims, the tubeless ready ones to some white ind hubs and those built up so fast and even it was a dream. They're still rolling smooth 3k later and the customer loves them.