Yes one could go as far as 205-60-15 or 205-65-15.
However the 684001-ES/164 wheels are designed for 185's.
195's would be optimal IMHO.

I tried 195-60-15's and they felt too short,and caused an early
slam shift on the 3-2 downshift in the BW-35.
It is a 240 Turbo size,and I would not recommend it.

I have just set up some 15 spoke 780 wheels
with Yokohama TRZ's in 195-65 -15.
Check Tire rack,they feel great,corner well,
and suposedly last a while.
This gives a 25 inch diameter wheel,and is close
to the stock 140 series 165-15 , 25.4 inch size.
Also +30 mm track,this gives better road feel,
a slightly wider stance,and better handling.


684001 & 140 wheels are 40 mm ET ,850 wheels would be closest at 43mm ET.
However I checked a 164 green book and the size was listed as 175-{80}-15.
Or 26.02 inches,a fairly large diameter wheel for a Volvo.
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71-145-S ; 72-145-E ; 72-1800-ES