i have a bike i haven't ridden since my concussion last year. i've always had something wrong with my shifting. before when i did ride my bike everyday, i began to notice that i couldn't use certaiin gears and that it was hard to engage all but the middle front chainrings. i didn't really mind at first, but now that i'm trying to ride again it seems my bike has gotten worse. the chain skips around from gear to gear on the cassette so i can't really pedal good. in the front i could only adjust the front derraileur so that i can engage to either just the middle and small chainring or the big and middle chainring. i tried adjusting the rear derraileur too, but the fourth to second chainring always have problems. the chain won't stay on those gears, it always has to jump to the next larger or smaller gear then back to whichever one it's suppose to, then do it again. i'm going to but grease so that i can install new cable line, but untill i get to, i was wondering if there could be anything else wrong. thanks for any help.