Personally I haven't had any issues with them. I did see one blow apart once but after looking over the tires on that car it looked like there was excessive camber being used which caused the blow-out. This past weekend I used Jaco Blues at the Canadian Indoor Nationals and finished 3rd in A main 17.5.
This was an open tire event. These tires worked great and had lots of grip. No complaints either.
RC America, HUDY, XRAY, JACO, Performance Hobbies, WERKS RACING, www.speedzoneusa.com, Sweep Racing USA