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12-speed SLX Derailleur Adjustment

The SLX derailleur on the Zulu Four HEIR is fairly easy to adjust. This guide will help you understand how to troubleshoot derailleur issues.

First, let's identify the different adjustments:

shimano slx 12 speed derailleur screws
View of the Derailleur from Directly Behind the Bike

 

shimano slx shifter barrel adjuster
View of Shifter from Top looking Down

Note the B Screw, L Screw and H Screw are adjusted using a 2mm hex key.

Here's how each of these adjustments function:

B screw:  Adjusts tension on the derailleur, between the frame and the derailleur (not to be confused with tension on the derailleur cable which is adjusted with the Barrel Adjuster).  The B screw adjusts the vertical distance between the derailleur pulley the rear cassette rear cassette.

To increase the vertical distance between the derailleur pulley and the cassette turn the B screw clockwise
To decrease the vertical distance between the derailleur pulley and the cassette turn the B screw counterclockwise
The SLX derailler has a line on the bottom of the derailleur cage (on the side of the derailler facing the wheel).  Shimano recommends adjusting the B screw so that that line lines up with the tip of the teeth on the largest cog on the cassette.

 

H screw:  Adjusts the limit for the derailleur on the smallest cog end of its movement.  Stated differently, when shifting into the smallest cog, the H screw determines how far inboard (towards the wheel) or outboard (away from the wheel) the derailleur sits.  The H screw should be adjusted so that when shifted into the smallest cog (highest gear) the derailleur pulley sits directly underneath the smallest cog.

When shifted into the smallest cog (highest gear)
To move the derailleur pulley inboard (towards the wheel) turn the H screw clockwise
To move the derailleur pulley outboard (away from the wheel) turn the H screw counterclockwise

 

L screw:  Adjusts the limit for the derailleur on the largest cog end of its movement.  Stated differently, when shifting into the largest cog (lowest gear), the L screw determines how far inboard (towards the wheel) or outboard (away from the wheel) the derailleur sits.  The L screw should be adjusted so that when shifted into the largest cog (lowest gear) the derailleur pulley sits directly underneath the largest cog.

When shifted into the largest cog (lowest gear)
To move the derailleur pulley outboard (away from wheel) turn the L screw clockwise
To move the derailleur pulley inboard (towards the wheell) turn the L screw counterclockwise

 

Barrel Adjuster:  Unlike the other adjustments, the Barrel Adjuster does not look like a screw.  Instead it is a barrel that sits around the shifter cable where the cable attaches to the shifter.  The Barrel Adjuster is designed to be adjusted with your fingers - you should not need to use a tool.

The Barrel Adjuster adjusts the tension on the cable, which in turn adjusts the indexing of the gears.  

If your derailleur hesitates when shifting into bigger cogs (lower gears), increase cable tension by turning the Barrel Adjuster counterclockwise.  
If your derailleur hesitates when shifting into smaller cogs (higher gears), decrease cable tension by turning the Barrel Adjuster clockwise. 

 

As always, if you have any questions or need help, never hesitate to contact us.

Other useful resources:

Shimano SLX Manual

Park Tool Video on Derailleur Adjustment