the rim size is the important number so depending on the size of your rim either 15'' or 16'' will determine what tires will work. If you have a 15'' rear rim only 15'' tires will work, and vs versa for the 16''. Also tire sizes for metric bikes use three numbers in this order width/profile/speed rating/rim size. A rim is usually made to only except one size tire however most of the time you can go up one size in width thats it. I would not recomend changing tires to anything other then the stock size unless you don't mind messing with unfavorable handling issues. Most bike handle best with the tire size they were designed for. Hope this helps and good luck.
