i bought my blaster about a month ago and i've been riding pretty regularly. the back brake doesn't work at all and hasn't since i've bought it, when i push the brake pedal down it doesn't even move on the brake parts. The fronts were fine but i was just riding this saturday and about two or three hours into it they started just locking up on me. i first thought that maybe some mud got in there and messed things up, but after i sprayed it down really good they're still doing it. also every once in a while the front brakes would make a weird noise kind of a griding noise but it more or less just sounds like metal on metal. anybody come across any problems like this? and is it hard to change the brakes on the blasters cause i wanna go again this saturday but i'm not going to if i'm about to flip over the front of it.