So I just got back into mountain biking and I bought an '09 Trek 4300...I took it to some trails and I like to ride particularly fast. Now, when going down hill on a turn, I notice I just don't get that good of traction. I even wiped out a couple of times where my back wheel went out. Are the stock tires any good? Should I upgrade tires or just accept that going downhill into a turn fast is just not gonna happen without my back end going out. Any recommended tires?