The derailleur hanger is the small metal part that holds the rear derailleur to the frame. It is made to bend before the derailleur or the frame does, so a fall, a knock in the car or a crowded bike rack can bend it. Once it is bent, the derailleur no longer sits in line with the cassette, and no amount of cable tension or limit screw adjustment will fix the shifting. The good news: you can check it and straighten it at home.
Signs your hanger is bent
- Shifting that will not stay indexed, however you adjust the cable
- The chain chatters, clicks or jumps a sprocket
- The derailleur looks tilted when you look at it from behind the bike
- The derailleur cage comes close to the spokes in the largest cog
- The trouble started after a fall or after the bike was transported
What you need
- The CycloSpirit Derailleur Hanger Alignment Gauge
- A hex key to remove the rear derailleur (usually 5 mm)
- A rag and a little grease
- A repair stand, if you have one: it keeps the bike level and the wheel easy to turn
Know the tool
- Tip screw (M10, replaceable): threads into the hanger in place of the derailleur
- Screw handle: turns the tip into the hanger
- Lever: the long arm you swing around the wheel, and the one you bend with
- Sliding bracket: moves along the lever and locks with its knob
- O-rings: markers on the indicator rod
- Indicator rod: its tip is what you set against the rim
- Ball plunger: sets how freely the handle turns
Before you start
- Remove the rear derailleur from the hanger. You can leave the cable on and let the derailleur hang out of the way.
- Check that the bolt holding the hanger to the frame is tight.
- Make sure the rear wheel sits straight and fully seated in the frame, with the quick release or thru-axle tight.
- Check that the wheel is true. Either way, take every reading at the same spot on the rim, next to the valve (see the tips below).
- Clean the hanger threads and add a little grease.
- Check that the tip screw (1) is tight on the tool.
- Tighten the ball plunger (7) until it is firm but still lets the screw handle (2) turn freely.
Step by step
-
Thread the tool into the hanger. Turn the screw handle until the tip is snug in the hanger hole, where the derailleur bolt went. Do not force it: if it binds, the threads may be damaged (see "When to replace the hanger").
- Swing the lever up to position A (12 o'clock) and turn the wheel so the valve sits next to the lever.
-
Set the indicator. Loosen the knob of the sliding bracket and slide it until the tip of the indicator rod just touches the outer edge of the rim, next to the valve. Tighten the knob.
- Mark the setting. Push the outer O-ring against the sliding bracket. If the rod moves later, you can put it back to this mark.
- Clear the rim. Slide the bracket down toward the hub until the indicator rod is clear of the rim and spokes.
-
Swing the lever 180 degrees to position B (6 o'clock) and turn the wheel so the valve follows. Slide the bracket back out to the rim and look at the gap between the indicator tip and the rim's outer edge.
-
Read the gap.
- Under 4 mm: the hanger is straight in this direction. Go to step 8.
- 4 mm or more, or the tip hits the rim: the hanger is bent. Slide the indicator clear of the rim and spokes, then bend the hanger with the lever, using gentle, steady force and a little at a time. Measure at A and B again after every small bend, and repeat until the gap is under 4 mm.
- Repeat steps 3 to 7 at positions C and D, behind the hub and in front of it.
- Final check. Set the indicator at one position and check all four. The gap should be under 4 mm at every one. If not, go round again.
Tips for an accurate reading
- Let the valve follow the tool. Turn the wheel so the valve is next to the lever at every position. You then measure against the same spot on the rim each time, so a wheel that is slightly out of true does not change the reading.
- Measure at the outer edge of the rim, not on the sloped sidewall.
- Bend about half the gap. Closing the gap at one position opens it at the opposite one, so a 6 mm gap means the hanger is out by about 3 mm. Bend toward closing half of it, then measure again.
- Small bends, steady pressure. Do not jerk the lever. Several small corrections are safer than one big one.
- A 4 mm hex key makes a quick gauge: if it slips into the gap, keep working.
- Rack, fender or frame in the way? Loosen the knob, pull the indicator rod back to clear it, then push it in again until the O-ring meets the bracket and tighten. The setting is unchanged.
When to replace the hanger
A hanger that survives a careful straightening holds up to normal riding. Replace it instead of bending it when:
- It is cracked, or it has been bent back several times. Aluminum gets weaker each time it is bent, and a tired hanger can snap during the alignment or later on a ride. Buy the replacement hanger made for your frame.
- The threads are damaged and the tip will not go in smoothly. A bike shop can clean them with an M10 x 1 thread tap.
If the hanger is part of the frame and cannot be swapped, bend it with extra care and in very small steps. If in doubt, ask the frame maker or a bike shop.
After the alignment
- Refit the rear derailleur and tighten its bolt.
- Check the limit screws and the indexing (cable tension) again: a straight hanger changes where the derailleur sits.
- Shift through every gear on the stand, then on a short ride.
Still not shifting well? Check the rest of the drivetrain:
- Chain wear, cleanliness and lube
- Wear on the cassette sprockets and the derailleur's pulley wheels
- Derailleur bolts tight and the derailleur cage straight
- The derailleur's return spring, with the cable off
- Shift cable and housing: rust, kinks or wear, and housing loops at the derailleur that are neither too long nor too short
- The shifter itself
Watch it done
Questions?
Use our contact form or write to support[at]cyclospirit.com. Bought the gauge? Register it for the 1-year warranty at warranty.cyclospirit.com.