I have the Cheng Shin tires and I am satisfied with them. I have good traction and disperse water extremely well (rooster tails) off the back tire. I also have a C50 and plan on putting tehe Cheng Shin on them also. Here is a good website for them:
http://www.kgmotorcycletires.com/cheng_ ... 6_c907.htm.
You can purchase them and have any local bike shop put them on. They will charge you for it with no complaints. Money is money. Expect to pay $25-$37 per tire for mounting and balancing. You may have to take the wheels off though. No big deaL, easy.