How to Adjust Rear Derailleur on Your Mountain Bike
To adjust the rear derailleur on a mountain bike, first, shift to the highest gear and loosen the derailleur cable. Then, use the barrel adjuster to align the jockey wheel with the smallest cog. Next, shift down to the lowest gear and use the limit screws to adjust the derailleur to align the jockey wheel with the largest cog. Finally, re-tighten the cable and make any necessary fine-tune adjustments with the barrel adjuster.