Quick answer

If your child's bike skips gears after a fall or a knock, the derailleur hanger is bent far more often than the derailleur itself. Straighten a mild bend with a hanger alignment gauge if you own one; otherwise fit a replacement derailleur hanger. Prevelo's hanger fits every Prevelo bike with a derailleur, so you can order with confidence.

Why the hanger bends before the derailleur breaks

The derailleur hanger is a small sacrificial tab bolted between the frame and the rear derailleur. It is designed to bend or snap so the frame and the derailleur survive a crash. That is good news for your wallet, but it also means a bent hanger is the first thing to check when shifting goes wrong. A hanger that is only a few millimetres out of line will pull the derailleur cage sideways, so the chain climbs or drops a cog at the wrong moment.

Diagnose before you buy

Put the bike in a stand or flip it upside down. Sight along the chain from behind the rear wheel: the derailleur cage should hang parallel to the cassette cogs. If the bottom of the cage points in toward the wheel or out toward the dropout, the hanger is bent. You can also shift through the gears slowly and watch the chain; skipping that appears in only two or three gears usually points to a hanger problem rather than a cable or cassette issue.

Straighten or replace?

A hanger alignment gauge is the only reliable way to straighten a hanger. If you do not own one, do not bend the hanger back by eye or with an adjustable wrench; aluminium work-hardens and can snap, leaving you with a broken hanger and a derailleur in the spokes. For most home mechanics, replacement is faster, cheaper, and safer. Prevelo's replacement derailleur hanger is a direct-fit part, and the product page notes that if you are unsure which hanger your bike uses, you should contact Prevelo before ordering.

How to replace the hanger

Shift to the smallest cog, then loosen the derailleur cable pinch bolt and remove the rear wheel. Use a 5 mm hex key to unbolt the derailleur from the hanger, then remove the two frame bolts holding the hanger. Clean the dropout faces, fit the new hanger, and tighten the frame bolts to the torque marked on the frame or in your bike's manual. Reattach the derailleur, refit the wheel, and reconnect the cable. Check that the derailleur body sits vertical before you index the gears.

When to stop and get help

Stop if the dropout itself is cracked, if the hanger bolts will not tighten, or if the frame threads are stripped. Those are frame repairs, not hanger swaps. Stop also if the derailleur cage is visibly twisted or the parallelogram has play; a new hanger will not fix a bent derailleur. If you have replaced the hanger and the gears still skip, the problem is likely cable tension, a worn cassette, or a bent derailleur, and a shop should look at it.

Symptom, cause, and action

  • Chain skips in two or three gears after a fall: The hanger is bent sideways, pulling the derailleur cage out of line. Sight along the chain from behind; the cage should be parallel to the cogs. If the cage is visibly angled, replace the hanger.
  • Chain rubs the next cog or drops off the largest cog: A hanger that is bent inward pushes the derailleur into the spokes or stops it reaching the low gear. Check for spoke rub marks on the derailleur cage. Stop riding until fixed; spoke damage is expensive.
  • Gears shift fine on the stand but skip under a rider: A hairline bend can hide when there is no load. Put the bike on the ground, have your child pedal, and watch the chain from behind. If it skips under load, replace the hanger.
  • Hanger is cracked or snapped: A broken hanger cannot be straightened. Remove the derailleur and fit a new hanger before riding. Replace, do not attempt to weld or bend.
  • New hanger fitted but gears still skip: The derailleur cage or parallelogram is bent, or the cable tension is wrong. Check the derailleur for twist and play. If the derailleur is bent, stop and see a shop.

Parts that fit this repair

  • Replacement Derailleur Hanger: Replacement Derailleur Hanger for all Prevelo bikes with derailleurs. If you are unsure which hanger your bike uses, please contact us. Note: Zulu Series bikes purchased before October 2018 use the Alpha Three and Alpha Four derailleur hanger. One part covers the whole Prevelo range, so you can order without measuring. The pre-October 2018 Zulu exception is the one case where you need to check before buying.
  • Zulu Frames: Prevelo Zulu frames are offered in three models — Zulu Three, Zulu Four, and Zulu Five — each available in Speed Silver, Bodacious Blue, or Pedal to the Metal Pink. These frames are built with the features listed below. Triple butted alloy tubes. Internal cable routing. Dropper post compatible. Universal Derailleur Hanger. Rear Thru Axle. Choose your model and color from the available options. If you are replacing a frame rather than a hanger, the Zulu frame uses a Universal Derailleur Hanger, which is a standard you can find at most shops. That makes future hanger replacements easier to source.