Bicycle Derailleur Adjustment
Rear Derailleur: There are 2 limit screws, one is the H labled screw and one is the L labled screw. The H screw sets the limit for hardest (hi) gear, the one with the fewest teeth. Set this with no cable attached. This is the natural gear for der. with no cable tension so you can adjust it by standing behind the bike and looking to see that the gears on the der. align with the hi gear. also check that your rear derailleur hanger looks to be straight.
Adjust the L lightest (low) screw. Push the der. to its inner limit with your thumb to see where it will allow the chain to go. If it will not reach the Low or biggest gear in the back then you need to loosen (counterclockwise) the L screw. If the chain goes over the last gear and down in the spokes then tighten the Low screw. Look from behind the bike and see that when the der. is pushed all the way in that the gear on the der. aligns with the gear.
There is a third screw, you can adjust it with the cable attached. It is called the b tension screw. It adds some tension to the spring, sometimes helpful.
Adjust the cable- shift your bike into its highest gear. Pull the cable tight. Shift the bike one gear. If it does not go to the next gear with the click try increasing the cable tension by screwing out the barrel adjuster, either on your der. where the cable housing stops or up on the shifter. Increase or decrease the cable tension to make the gears shift quicker.
Flourinated greases are good to lube the inner cable with. Tri flow works pretty good too. If you develop corrosion on your cables you can use a scotch bright or steel wool to remove it or you could replace your cables at some point.
the front der. adjustments are basically the same procedure, just takes aligning the cage of the derailleur with the chainring. L is your inner smallest ring and H is the big ring. tightening H will prevent the chain from coming off the outside of the big ring toward your pedal and tightening L will keep the chain from falling off on the inside toward the frame. Tweek the cable tension to make the gear go up when you click it. Adjust the cable with shifter barrel adjuster or by pulling the cable tighter at the pinch bolt.