DIY Adjusting the Rear Derailleur On an Electric Bike

by | Aug 24, 2021 | Electric Bike - General Maintenance

Electric bike riders, when confronted with a shifting problem, may think that a bike shop is the only answer to fixing the problem. However, this may be a problem that can be solved by the rider.

A shifting problem can occur due to a misalignment of the derailleur. With a few simple adjustments the shifting problem can be fixed and the ebike back on the road again.

DIY Derailleur Alignment

When encountered with shifting problems, such as excessive noise, slow shifting, or no shifting from cog to cog, these can be solved with a few derailleur adjustments, such as:

  • The limit screw adjustments (H-limit and L-limit)
  • Indexing
  • The body angle screw (B-screw) adjustment.  

All that is needed is a screwdriver or hex wrench and a way to hold up the bike, such as a repair stand, to check the adjustments.

H-Limit Screw Adjustment

Before starting this alignment make sure the derailleur hanger is not bent. The H-Limit adjustment is usually the upper screw as shown in the picture above.   

  1. Shift the derailleur to the biggest front chainring and the smallest rear cog.
  2. Keep shifting the shifter until there are no more clicks.  This ensures the shifter is fully actuated outward. 
  3. If the chain does not move to the smallest cog, turn the H-limit screw a few turns counter-clockwise.
  4. Pedal and see if it makes the shift outward
  5. If it’s still not shifting outwards, turn the barrel adjuster clockwise a few rotations.  The barrel adjuster is located on the derailleur and up at the shifter.
  6. Pedal to see if it shifts.
  7. When the chain is on the smallest rear cog and the shifter is not clicking, turn the barrel adjuster a couple more times clockwise to add slack to the cable.
  8. If the limit screws aren’t labeled, tell them apart by turning each screw.  The screw that causes the derailleur to move is the H-limit screw.
  9. Tighten the H-limit screw a half-turn, pedal, and listen for noise.  If there is no excessive noise while pedaling, the H-limit screw is not tight enough.
  10. Tighten the H-limit screw another half-turn.  Again, pedal and listen for excessive noise.  If excessive noise is heard, check to make sure the chain is rubbing against the cog next to the smallest cog.  Sometimes an overly tight limit screw will cause a shift to the next cog while pedaling.  Loosen the limit screw until it shifts back and creates excessive noise while pedaling.
  11. Once the excessive noise is heard, loosen the limit screw a quarter-turn at a time until the noise is gone.  If two settings are equally quiet, turn it to the tightest of the two settings.
  12. After the H-limit screw is adjusted, turn the barrel adjuster a couple of times counterclockwise 

L-Limit Screw Adjustment

The L-Limit screw is usually the lower adjustment on the rear derailleur as shown in the picture.

  1. Shift to the next smallest chainring in the front.
  2. Shift to the next largest cog on the rear.
  3. Shift to the largest rear cog.  If the chain doesn’t make the shift, the L-limit screw is already too tight.  If the chain is slow to move to the largest cog, this is also indicative of a too-tight screw.  If there is excessive noise once the shift is made to the largest cog, this also means the L-limit screw is too tight.  However, having a too-tight screw is the desired position to start the adjustment procedure.
  4. If the shift is made properly from the next largest cog to the largest cog, tighten the L-limit screw-in half-turn increments until excessive noise is heard.
  5. Once excessive noise is heard, loosen the L-limit screw in quarter-turn increments until it shifts quickly and the excessive noise is gone.

B-Tension Screw Adjustment

B-screw adjusts the spacing of the G-pulley or guide pulley to the cogs that should be between 5 and 6 mm.  However, if the bike is shifting properly, the B-screw doesn’t have to be adjusted.

  1. The chain should be on the smallest cog in the front and the largest cog in the rear.
  2. Gauge the spacing with a hex wrench.
  3. To increase the gap, tighten the B-screw.
  4. To close the gap, loosen the B-screw.
  5. If significant changes were made with the B-screw, check the indexing for proper shifting.

Indexing

Indexing is the process of adjusting the slack in the cable to align the guide pulley with the cogs so that each shift lines up perfectly with the gear and cog.

  1. If there are two front sprockets, shift to the largest.  If there are three front sprockets, shift to the middle.
  2. Start on the smallest rear cog.
  3. While pedaling, shift the index shifter one index click, no more than one click.
  4. If the chain did not move to the next cog, turn the shift lever to the outermost click.  Turn the barrel adjuster a full-turn counterclockwise.  Try it again and repeat the steps until it makes the shift.
  5. Once it makes the shift, take the slack out of the cable at the pinch bolt.
  6. If the chain shifts two cogs instead of one, turn the barrel adjuster one full-turn clockwise and try to shift again.
  7. Once it shifts the way it’s supposed to, turn the barrel adjuster counterclockwise outside the acceptable adjustment range.  This will be indicated by excessive noise.  Turn the barrel adjuster until excessive noise is heard.  Check to make sure the excessive noise is from the chain striking the next shift cog.
  8. Turn the barrel adjuster quarter-turns clockwise until the excessive noise is gone.
  9. Shift to all rear cog positions to make sure excessive noise is not heard on any shift.  If excessive noise is heard, turn the barrel adjuster a quarter-turn clockwise until all excessive noises are gone on all cogs except for the largest one.
  10. If the chain is slow to move on to a cog, this can be fixed by another quarter-turn clockwise of the barrel adjuster.