Don't know if similar applies to the SS but on my 900 Monster, the chain runs very close to the edge of the tyre. So close that if the chain is loose it will contact the tyre edge and, obviously this is more pronounced with a wider tyre. When I first got it, seeing as it has a 5.5" wheel like the 916, I tried a 180 but deemed it too close to the chain so went back to a 170. It's not like the power is going to overwhelm the grip of a modern tyre.
This would also depend on chain tension settings. A newish chain would have the tyre closer to the swing arm loop, and OE hugger
