Probably doesn't affect it at all. If anything, (theoretically anyways) the 170 should handle better than the 180. I may turn in a tad bit faster and feel more responsive & lighter, but may never be anything you would feel on the street. Does it have a 5 1/2 wheel on it? Are you SURE the bike didn't come with a 170? I'm not sure, so just asking cause my SS has a 5 1/2 wheel on the back but comes stock with a 170. I changed to a 180 and like it better but that's another story.