How to Check a Bike's Hanger Alignment

If you crash on the right side of your bicycle, there's a good chance that you'll bend the rear derailleur hanger and your bike will no longer shift properly. If you have a steel or titanium frame and the proper tools, this is a relatively easy repair.

Instructions

Difficulty: Moderate

Things You’ll Need:

• Break-away Bolts
• Bike Grease
• Bike Repair Stands
• Bike Tools
• Derailleur Hanger Tools
• Allen Wrenches

Assessing the Problem

1. Determine whether this is a fix you can make. Did you crash on the right side? Does your rear derailleur shift poorly or appear to be bent inward? If so, your hanger is likely bent.
2. Stop now if you have an aluminum frame. Many aluminum frames have a replaceable hanger. If so, replace the hanger.
3. Bring your bike to a qualified mechanic to evaluate the situation before you try to bend it back if your aluminum frame doesn't have a replaceable hanger, since aluminum often breaks before it bends.

Repair the Hanger

4. Assemble the proper tools. You will need a repair stand and a hanger alignment tool. You may also want a true rear wheel without the tire.
5. Clamp your bike in a bike stand (drivetrain facing out).
6. Install the wheel without the tire (optional).
7. Shift into your smallest cog and, using a 6 mm Allen wrench, unbolt your rear derailleur.
8. Inspect the hanger threads for damage. If they're undamaged, thread in the alignment tool.
9. Rotate the tool, measuring the space between the tire or bare rim all the way around. It should remain constant.
10. Carefully bend the hanger back into proper alignment if the distance between the tool and the tire or rim varies, by pulling outward on the arm of the tool.
11. Double check the alignment again.
12. Remove the tool once the hanger is properly aligned.
13. Grease the threads and install the rear derailleur. If the rear derailleur is adjusted properly and not damaged, it should shift smoothly now.