so i was out riding my 02yz426. chain got loose and wrecked the Sprockets. so now i have to get new ones and needed a little feed back. on the bike now i have a 51 tooth rear. i see stock is 49 for the yz and 50 for the wr. now i ride in the woods in michigan, and wanted to know what a good number front and rear is? and should i go steel or aluminum? my buddy i ride with says steel. and whats a good brand and where the heck should i get them from?