Seems like one member went to the darkside with a 180/??-15 car tire, and just managed to fit it on. I don`t recall the aspect ratio or the brand right now.
The 170/80-15 mc tires of most brands seem to fit according to reports on this board.
I wouldn`t recommend anything wider. As it is the 150/90 is the stock size tire for much larger cruisers including the older vn1500s I believe. Not sure why you would want a wider tire than the 170 anyway.
I also read of another member blowing up their rear rim with a oversized car tire. Be careful fitting them!
1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Rebuilt Forks w/ Progressive Springs
VN750.com Grill Cover
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R
1990 Kawasaki Vulcan 750
1998 Honda VFR800 FI
2014 Honda VFR800F
1989 Pontiac Firebird Formula 350