Tire mounting q:
 

Uniformity Method
When performing uniformity match-mounting, the red mark on the tire, indicating the point of maximum radial force variation, should be aligned with the wheel assembly's point of minimum radial run-out, which is generally indicated by a colored dot or a notch somewhere on the wheel assembly (consult manufacturer for details). Radial force variation is the fluctuation in the force that appears in the rotating axis of a tire when a specific load is applied and the tire rotated at a specific speed. It is necessary to minimize radial force variation to ensure trouble-free installation and operation. Not all wheel assemblies indicate the point of minimum radial run-out, rendering uniformity match-mounting sometimes impossible. If the point of minimum radial run-out is not indicated on a wheel assembly, the weight method of match-mounting should be used instead.

Question is does the factory rims have this mark?

Weight Method
When performing weight match-mounting, the yellow mark on the tire, indicating the point of lightest weight, should be aligned with the valve stem on the wheel assembly, which represents the heaviest weight point of the wheel assembly. After match-mounting by either of the above methods, the tire/wheel assembly can be balanced

Re: Tire mounting q:
 

I'm not sure if the factory rims are marked. I do know that very few tire installers even know what the marks are for let alone install the tires correctly.
When I have had the marks properly aligned I'm sure it was totally by random chance and not by any intelligent planning.

Re: Tire mounting q:
 

The uniformity method is something I rarely used back in my tire mounting days, mainly because new wheels are infrequently marked, and I seldom had time to examine old wheels for any indications.

I don't know how true the weight matching method is, for a couple of reasons:

1. If the valve is meant to show the heaviest point on the wheel it should basically be randomly clocked around the wheel circumference, at least as much as is allowed by the spoke layout (for example, a 5 spoke wheel would only have 5 possible valve locations). This may be the case with steel wheels, but every aluminum/alloy wheel I've ever seen has the valve located at a point that is the same relative to other details on the wheel that are part of the casting process. On my BBS wheels the valve is two spokes to the left of the size marking on the wheel, every time. How can the balance of the wheel be known before the forging process is carried out?

2. I could often obtain a better balance by positioning the tire somewhere other than the alignment marks. I would always start using the valve to line the tire up, but if the balancer demanded an unacceptable amount of weight I would reposition the tire. The rate of occurrence was high enough that there was no clear indication that lining up the valve with the mark on the tire made any difference.