I just got a cranbrook real cheap and like when I was a kid I wanna change it into a bmx cruiser type my question if you may the rim om the bike now are super clean Crome but the rear tire has a crack in the middle threats so I wanted to change them the size is (57-559) 26x2.125 will any other size work as long as its 26" tire not to versed on the big tire and what the 2.125 means any help or advise will be appreciated. Also do the tire have to be each cruiser tire