hey guys my 81 has 5700 original miles great looking bike, but my rear tire is getting down there, i´ve never bought tires for a bike before wonder where is the best place to look? the size is a 4.60-16 or mp85 and other metric sizes 120/80-16 120/90-16 110/90-16. Just wondering where the best spot is to look and maybe a recommendation for a specific tire you used and got good miles out of and good grip? thanks