Bicycle Mechanics - AARRRGGGHHHH dam it

i have just started freeriding and hav ebought a Saracen Mantra(LE). ever since i got it the rear deralliur(however you spell it) has been switchin from one gear to another and i am whackin my bits off the top bar. i have tried to reallign the deraliur but it has done nothin at all. any other suggestions you lot.
please help.

thanks very much

Removing the slack in the cable will do fine.

:beer:

Yeah. Twist the little knobs on the cable (theres one by the derailer and one near the fork). Just twist 1/4 turns at a time to make sure you don't over do it. Spin the pedals and shift through all the cogs to and repeat untill each shift is smoothe and the chain stays on the cogs without any interuptions. Also, make sure you aren't tightening/loosening the brakes or front derailer. :D

Follow this link, and read my directions for installing/adjusting both of your derailleurs! or, www.parktools.com has some good instructions.

Adj Derailleurs (http://www.bikeforums.net/showthread.php?s=&postid=162234#post162234)

i have got SHIMANO DEORE derailer and SHIMANO STXRC shifters. i dont know of this helps you. ijust payed £65 to get these fitted and they aint done it properly

thanks for the advice but it aint made any difference. one thing i did notice was that the chain is catching itself up and the deraileur is flicking to get the chain tight again. what does this mean. if its serious im chucking the bike away.nothin but trouble.

solved it!!!! the chain was way toooo long for the bike. i had to take 8 links out until it was perfect. it just needed a bit of fine tune after that!!! THANKS ANYWAY