Just removed the stock 195 tires from my 92 400E, and fitted 215/60R15 tires on my 15" stock rims.

All I could say is that they fit perfectly, the stock rims are 6.5" wide, most of the 215/60R15 tires can fit 6-7" wide rims.
Actually when Michelin calculates the section width for their 215 tires, they use 6.5 rim, that means the 6.5" rims are quite normal for 215 tires.

For those who don't want to invest extra on new rims, I would strongly recommend 215 tires on stock rims.

I put Michelin Arctic Alpines on my car, though I know the performance on snow degrades with the fatter snow tires, but it definitely greatly improved my overall dry road handling, also my 400E looks much better than before.

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99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.