I just got some 15" alloys to replace my steel wheels and had my local tyre shop swap the tyres from the steelers onto the alloys- I noticed afterwards when I got home there were no weights on the outside of the wheels. I did a 130 mile journey the same day at speeds up to 95mph and noticed no vibration etc.
I'm not sure if they put balancing weights on the inside but if not should it pose a problem?

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1994 E300D S124 OM606 Estate/Wagon 'Green Machine 2' 120,000 miles

2001 Gary Fisher 21-speed ? miles
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past:

1983 230E W123 M102
1994 E300D S124 OM606
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
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"music and women I cannot but give way to, whatever my business" -Pepys