How do you adjust a rear derailleur without a barrel adjuster?
With no cable, put the chain in the small ring and big sprocket. Adjust the inner stop so that there is just the minimum of clearance to the chain. With the shifter in the released, small ring position, hold the end of the cable with pliers and put some tension on it as you tighten the clamp.
What does the B screw do on a rear derailleur?
Simply put, the B-Tension screw is there to control the gap between guide pulley (the upper pulley on the derailleur) and the bottom of the cogs.
Which way do you turn a barrel adjuster rear derailleur?
This rule will help you remember which way to turn it: If the derailleur is hesitating when shifting toward the spokes (the more common problem), turn the barrel toward the spokes (counter-clockwise); and if it hesitates shifting away from the spokes, turn the adjuster away (clockwise) from the spokes.