If you've ever observed a wheel balance being carried out, you will note that the machine records the 'out of balance' weights for both inner and outer rims. The best possible balance is achieved by placing the correct adjusting weight as close as possible to the outer edge of the rim. Most tyre fitters will use stick-on weights on the rim as close as possible to the outer edge, behind the spokes, but will avoid putting them on polished rims because people tend to get a bit pissed at having little lumps of grey stuff stuck on their sexy rims. But it is a compromise on achieving the best possible balance, especially with deep dish rims.
June 88 535iA, 173,000 km; Sep 00 735i 170,000 km