Hi, I need to replace the tires on my 1988 Suzuki Intruder 750. The existing tire says, 3.00 - 21 which must be a 21 inch tire, right? Well all the specs I check online show it should be a 19 inch tire. Anyone know what´s up with it? It was purchased like new in January 1989 from the friend I bought it from. Ideas? Suggestions?