So I bought a 2010 U.S. made RZ120 4 and I love it! I took it out yesterday right after I bought it and it climbed amazingly! However, when I was going downhill, my brakes felt like they couldn't stop me if I needed to quickly stop. It was hard to brake on turns and it felt like these things were as bad as my crappy walmart bikes brakes. Am I doing something wrong? Or do the brakes suck? They're Shimano BR-M486's. Would an upgrade be a good idea?