How To Adjust a Mountain Bike Rear Derailleur
Whether you mountain bike down edgy rock gardens or slog out singletrack switch backs, glitchy gears can aggravate. Since, they are also dangerous, it is important to adjust the rear derailleur of your mountain bike right away.
Tools you will need:
5 millimeter allen key
Needle nose pliers.
Cable tension tool (not essential, but handy)
There are 3 screws on the rear derailleur body used for adjustment.
The H screw-one of a pair at the rear of the derailleur body.
The L screw-in a pair with the H screw at the rear of the derailleur
The B Screw- usually underneath the parallelogram body.
Begin by opening the cable clamp using the 5 millimeter allen key relieving
the rear derailleur of all tension.
This should allow the rear derailleur to hang directly below the frame.
The top pulley wheel, known as the jockey wheel, should be right below the outside cog in line with the drive side rear triangle of the bike. If pulley is not in line, try turning the H screw counterclockwise to align it with the chain. Turn the cranks moving the chain to check chain flow and alignment.
Once pulleys are aligned with frame and outside most rear cog, try the
lowest gear or innermost cog. Since it is still without any cable tension, the derailleur cage must be manually moved.
Testing the high and low adjustments.
Manually turn the cranks to ensure that it doesn't jump or move into the wheel
or off of the largest gear. Make sure the barrel adjustment on the shifter is fully screwed in against the derailleur body. That way you as much screw to adjust as you tune.
Tighten the cable clamp on the derailleur.
You can pull the cable taut with your fingers or you use the cable tension tool-- but you can literally just use your hand. Then turn the clamp bolt tight without over-tightening.
Make sure you have enough cable to throw the derailleur cage to the next
several gears. Manually push your derailleur cage to see if you you have enough to travel to go through all the gears. Then, cut your cable approximately 1 inch past the clamp bolt. Putting a nipple on your cable end will prevent fraying.
Fine tuning shifts.
Click the shifter once to see how much the derailleur moves and how much
move cable it uses. Circle the petals around and then click the indexed shifter one gear. If the chain doesn't move over properly then turn the internal barrel adjuster a quarter turn at a time until it does.
Try that up each gear and then and then try back down again for all of
them. If it is going too far then you need to reduce the cable tension at the
barrel adjuster. You might hear a slight noise coming from the chain after you adjust. That is probably coming from the front derailleur. To check out a repair tutorial, click on the front derailleur on the bicycle diagram on the front page.