hi, i need to set up the front and rear derailures on my giant defy 5, the chain is slipping when i am moving into higher gears on the small ring at the front, i adjusted the tensioner on the rear derailier until it seems ok, then when i moved into the big ring on the front it was doing the same again on the rear. i have removed the crank arm to clean the bottom bracket will this be the problem? i do want solve the pronlem myself so i am not going to pay a shop every time something needs fixing, or am i better off taking to a shop