Thing can go bad in a heart beat at 30 mph. At high speeds, you want to have a lot of experience and even then, a flat tire or broken rim and you are GONE. Slalom racing and road courses put tremendous side loads on the rims that they seldom get in normal road use. I've seen pictures of the centres broken out of factory wheels. If you plan on racing or aggressive stuff, get race parts. There is a reason why forged parts are used in hipo and race engines. Forged wheels for the same reason. You might get away with cast stuff for a while but it will bite you eventually. Around here years ago stock car guys were using Corvette rally wheels at the local 1/4 and 3/8 mile oval tracks. So many centres were getting broken out of these wheels that they were banned. Fine for the street but not for race applications.