This episode of Fools with Tools is the first of our two-part series on derailleur tuning. If your derailleur is acting up, check out these tricks to fix your noisy, click-y, skipping shifting so you can pedal in peace and have access to all of your gears!
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How to Adjust Limit Screws
- Begin by shifting through your gears to find where the skipping, clicking, or lagging is coming from.
- Once found shift into hardest (smallest) gear.
Now identify the High (H) limit screw. This is typically labeled with an H and the Low limit labeled with a L. Note: Clockwise turns will limit outboard movement and counter-clockwise turns will increase outboard movement. Ideal high limit is where chain sits comfortably on smallest cog without any clicking or noise, and then turn extra half rotation counter-clock wise.
- Now it's time to check your Low (L) limit screw. Do this by shifting into easiest (largest) gear.
Using you thumb on the parallelogram, gently apply pressure onto derailleur to check for improper low limit.
Note: If chain begins to derail off back of cassette, low limit screw must be turned clockwise in order to limit the derailleurs inboard movement. If derailleur has trouble getting into the easiest gear, such as the chain riding on top of the teeth, or the shifter gets very tight when going into easiest gear, the low limit screw is too high and will need to be turned counter clockwise.
- Repeat step 5 until chain rides smoothly on easiest gear without falling off back of cassette if derailleur is pushed inboard.
How to Adjust B-Tension
- 3mm Allen
- Tool that may come with your derailleur*
- Begin by shifting into easiest (biggest) gear.
- Using B Tension screw, adjust the gap between upper guide pulley and largest cog to the appropriate spec.
*Note: Some derailleurs have a tool for finding this setting, some have it etched on the back of the cage, and others use a specific measurement. Shimano 7-11 speed requires 5-6mm gap and Sram 11-12 speed requires 13-15mm. Shimano 12 speed measures at 46-52mm from center of guide pulley and tip of teeth in largest cog.
How to Adjust Cable Tension
- Begin by shift through your gears to test their function. Start in hardest cog, then shift through gears one by one. For each, be on the lookout for abnormal clicking, skipping, and lagging.
- If your chain is moving up cassette with very little force being applied on shift lever, cable tension is too high and will need to be decreased. To do this spin the barrel adjuster clockwise.
- If the chain is hesitant to move up cassette, or frequently wants to drop back down into smaller gear, cable tension is too low and should be increased. To do this spin the barrel adjuster counter-clockwise.
- Repeat steps 3-4 until shifting is smooth and consistent across all of your gears.