i was playing around with my bike trying to see how things work and i goofed up. now my chain rubs on the front derailleur when i am on the smallest cog in the rear and largest in the front. how do adjust it. if i shift into a larger size sprocket it still rubs on the 2nd smallest. only the third and up doesn't rub. tried twisting this thing near the shifter and i saw two small screws on the derailleuer as well. i don't know which one to adjust. or is it my rear der? the chain rubs on the metal plate, the one that is farthest out (closest to pedals) on the derailleur.