nmnm wrote:Beware with alu frames, it's quite possible to break the fragile hanger in the process of removing/reattaching the mech. I almost sheared the thread at the airport this year on day 1 of my hol. I bought a spare hanger as soon as I got back - hangers are quite tricky to buy (many different shapes that won't fit your frame) and broken/sheared hanger = no chain tension = no pedalling.BeeKeeper wrote:Removing the derailleurs is a sensible thing to do - it reduces the chance of them being damaged.
Taking a spare hanger is a good idea in any case. But if your frame has replaceable hanger, better than removing gear mech from hanger: leave the mech attached to the hanger and instead remove hanger from frame!
This makes the hanger even less likely to get bent or broken, but more importantly it eliminates any risk of damaging those fine threads when re-attaching the mech. The hanger will usually be secured by fasteners that are much easier to re-fasten without risk of cross-threading than the fine-threaded mech bolt. You will have to take the wheel out to get at these fasteners, which makes the packing and assembly jobs take even longer in situations where the bike may travel with this wheel in-situ. But if it avoids damage, it's worth it.
Even those who do NOT have a replaceable hanger may find it advantageous to remove their rear wheel BEFORE attempting to re-attach the rear mech. This avoids all of the struggle with chain tension whilst you try to line up the mech bolt with the hanger, which is the usual cause of mis-aligned assembly, AKA cross-threading.