In the latest Audax UK magazine ‘Arrivée’ there is an article by Neil Goldsmith about his experiences as principal mechanic at the remote Eskdalemuir control assisting the 1500 riders on the 2017 London-Edinburgh-London ride. Here is an excerpt from it.
“We had one rider who had broken his gear hanger. Unfortunately there was nothing we could do for him. All carbon, aluminium and many titanium frames have replaceable gear hangers. A gear hanger is a sacrificial part designed to break to save the frame. There are around 200 variations of gear hanger and bike shops buy them in to order. It is a roadside repair to change a gear hanger if you have one with you, and impossible without a hanger which fits. Gear hangers are easily sourced online. I regard them as an essential spare to carry along with spare tubes.”
They are very small and light and can get you home.