I own a Raliegh mountain bike that I purchased about two years ago. I noticed that the last time I went trail riding, there is a noise coming from the pedal area. I'm not sure if it is the pedals themselves, or if there is something wrong internally, but it makes a squeaking noise and skips every so often. I know that it isn't the chain or the gears because I have had them looked at. Any thoughts on what could be wrong?