A rear derailleur hanger is a replaceable parts, made out of alloy, that links the frame and the rear derailleur together. In case of an impact to the derailleur, the hanger will sacrifice itself in order to protect the frame and derailleur as much as possible. If you feel like your gears all of the sudden have gone bad, the most likely cause is a bent hanger, caused by an impact to the frame/derailleur. In this tech guide, we will cover the basic steps to replace a hanger and make your gears perfect again.
Part One – Removal of the damaged components
The first step is to remove the damaged parts that we no longer need. There will be a small, torn piece of alloy attached to the Rear Derailleur (otherwise known as rear gear changer mechanism) You can do this by holding the torn piece of alloy with pliers or vise grips, anything that gives a firm hold. Then using a 5mm allen key, turn the centre bolt that screws into the torn alloy piece Anti-Clockwise until all the threads have pulled away leaving the scrap alloy piece in your grips.
Now you want to remove the rest of the destroyed replacement hanger. If you remove the rear wheel, and look at where the rear derailleur came away from the frame- you will notice the rest of the alloy hanger attached to the frame by 2 small [M3/2.5] fasteners. If you undo the fasteners you can remove the rest of the hanger.
Part Two – Installation of new replaceable hanger
With the old hanger disposed of, you can now attach the new provided hanger. Using the 3mm allen key, unscrew the 2 fasteners and insert the new hanger behind the frame just as the damaged one you previously removed was.
Now insert the 2 fasteners in place and tighten until snug – you do not have to over tighten these fasteners as they are very delicate and can break easily.
- The new replacement hanger is ready for use.
Part Three – Installation of rear derailleur
Hold the rear derailleur up close to the new hanger, You will notice there is a small lip at the bottom of the hanger where the hole & threads are for the derailleur to screw into. This lip is for the derailleur Limit Screw A. The limit screw is visible on the derailleur at the back next to the threads where the derailleur screws in. You need to position the A Limit so that the end of the A Limit screw is sitting against the lip of the hanger.
- With the derailleur in position, proceed to screw in the rear derailleur to the hanger using a 5mm allen key until snug. Provided that the (B) limits of the original derailleur are not altered, the shift indexing should be accurate. If shift indexing is not accurate, then the rear derailleur needs to be reset.