Always inspect for damage or loose bolts/parts before proceeding. Never lay the bike down on the drive side. It is always advised to keep your drivetrain clean and lubricated to get the best performance. If you think shipping damage has occurred, or something is functionally wrong with the derailleur out of the box, do not ride the bike and report to us immediately at: firstname.lastname@example.org
Rear Derailleur Tuning:
- The most common shifting issue on new bikes is dealing with “cable stretch”, which is all the housing, ferrules, shifter and derailleur parts, and cables finding their final resting place during the initial break-in of the bike. Typically, the tension on the cable is reduced during this process, so you will turn the barrel adjuster on the rear derailleur outward in small increments until the chain chatter is gone and all gears are adequately reached during shifting. For our Shimano mechanical 2x builds, Shimano front derailleurs have a built-in tension adjuster which requires a 2mm allen key; tightening it will add cable tension.
- Ensure that the notch behind the main derailleur fixing bolt is hooked above the notch on the derailleur hanger when installed. Ensure that the batteries are charged, and units are connected/wires are plugged in for electronic groupsets.
- If the chain is chattering, check for a bent or loose hanger, a loose derailleur fixing bolt, or visible damage to the derailleur. If these look normal, try using the barrel adjuster on the derailleur, ideally while pedaling the bike in a stand. Turning it out will put more tension on the cable and move the indexing up the cassette (toward the bigger gears), and turning it in will decrease tension on the cable and move the indexing down the cassette (toward the harder gears). Continue adjusting until the chattering is gone and each gear is still properly reached during each shift.
- For Di2 derailleurs, indexing adjustments are made by holding down the button on the bar end unit until it flashes rapidly (a couple seconds), then use the shifter itself to move the indexing up or down. Hold the button again to exit adjustment mode and test the chattering and gear shifting. Repeat until quiet and shifting is optimal.
- For AXS derailleurs, simultaneously hold the shifter button and use the shifter to move the indexing up or down. Release the button to exit adjustment mode and test the chattering and gear shifting. Repeat until quiet and shifting is optimal.
- If lagging, chattering, or falling off in the hardest (smallest) rear cog, adjust the high limit screw so that the upper derailleur pulley is directly aligned with the hardest cog. If lagging, loosening the screw is the fix here; if falling off, tightening the screw is the fix.
- If lagging or falling off the easiest (biggest) rear cog, adjust the low limit screw so that the upper derailleur pulley is directly aligned with the easiest cog. If lagging, loosening the screw is the fix here; if falling off, tightening the screw is the fix. It is especially crucial not to loosen the low limit screw too much in order to avoid throwing the chain and derailleur into the rear wheel spokes.
- If chattering or grinding occurs, especially at the easier end of the cassette, the b-tension screw must be tightened so that the upper pulley does not touch the next easiest cog during shifting.
- If overall lagging during shifting is occurring, regardless of up or down shifting, the b-tension screw may be screwed too far in, pulling the upper pulley too far away to guide the chain adequately up and down. If your bike is thoroughly used, you could have worn drivetrain parts, or too much grime in the system.
Front Derailleur Tuning:
- Ensure that the front derailleur and derailleur mount bolts are tight, properly angled to align with the chainrings, and is the correct height so that it clears the big chainring with only a small gap remaining (1-2mm). Check for damage to the chain (breaks, kinks, rust, stiff links) and make sure the quick link is fully snapped in place. Check for bent chainring teeth, loose chainring bolts, loose crank, and derailleur damage. For thoroughly used bikes, the front derailleur cage could now be warped outward into a more oval shape rather than a rectangle due to overuse, often causing shifting lag or chain drop. Di2 front derailleurs can have indexing adjusted by holding down the bar end unit button until it flashes, and using the front shifter to slightly change where the derailleur cage rests after shifting; always ensure the wires are connected and the battery is charged. AXS front derailleurs do not have index adjustments, so only limit screws, positioning, damage, disconnected units, dead battery, or updates are to be considered for fixes.
- If chain is rubbing:
- First make sure you are adequately using the trim adjustments in the front shifter to see if this alleviates the issue
- Inside while in small chainring: requires either less cable tension or loosening the lower limit screw until the derailleur cage no longer touches the chain. If it no longer rubs, but now does not reach the big chainring, there is either too little cable tension, or the derailleur angle/height is wrong.
- Outside will in small chainring: this is typically due to cross-chaining, one example of which is when you are in the hardest rear cog but still in the smallest chainring. It is recommended to use a different gear combination than this, although trim adjustment on the front shifter can often eliminate the noise. However, if it is still occurring further up the cassette, either more cable tension is needed, or the derailleur angle is wrong.
- Inside while in big chainring: this is also most often caused by cross-chaining, but in the other extreme chain angle, which is the big chainring and easiest cog. It is recommended to use a different gear combination than this, although trim adjustment on the front shifter can often eliminate the noise. However, if it is still occurring further down the cassette, either less cable tension is needed, or the derailleur angle is wrong.
- Outside while in big chainring: requires either more cable tension or loosening the high limit screw until the derailleur cage no longer touches the chain. If it no longer rubs, but now does not adequately shift to the small chainring, there is either too much cable tension, or the derailleur angle/height is wrong.
- If chain is dropping:
- Inside off small chainring: tighten the low limit screw until the derailleur cage is barely not touching the chain while in the easiest cog. If it still drops, the derailleur angle or height could be wrong, or there is damage or looseness to some part.
- Outside off big chainring: tighten the high limit screw until the derailleur cage is barely not touching the chain while in the hardest cog. If it still drops, the derailleur angle or height could be wrong, or there is damage or looseness to some part.
- If not able to shift into one chainring, either increase/decrease the cable tension, or loosen the corresponding limit screw. The derailleur angle or height could also be wrong.
This page is primarily written to address new bike issues, not thoroughly used drivetrains. If something was not adequately covered here, or this list did not provide enough aid for your particular situation, please either visit a local bike shop or email us at: email@example.com