I don’t know too many mountain bikers who keep a replacement derailleur hanger in their pack and there aren’t many mechanicals that can more immediately strand a rider than a broken derailleur hanger. That’s where the SRAM UDH or universal derailleur hanger comes in.
SRAM designed the UDH to fit within the established parameters for every drivetrain on the market, and the number of brands that have adopted it is remarkable. Among them: Canyon, Devinci, Evil, Factor, Ibis, Niner, Pivot, Rocky Mountain, Santa Cruz, Scott, Yeti, and perhaps most significant, both Specialized and Trek have signed on.
So I’m not advocating that everyone rush out and buy this $16 hanger. Lots of bikes out there won’t accept it.
I’m bringing it to your attention for two reasons: First, I think people shopping for a new bike should keep an eye on this as a feature worth looking for. The hanger, if it hits something, is designed to rotate, creating an opportunity to escape destruction. Also, if the chain falls off the smallest cog, it’s designed to make the chain ride in a way that will feed it back onto the smallest cog.
I know riders who will keep stuff on them that they may never need, but consider this. The UDH is just the sort of part that could help a stranded friend ride out of the woods. Even if you never need it, it’s a little thing that might make you the hero of a ride that doesn’t need to end with a long walk back to the car. Given the fragility of many derailleur hangers, it seems like a worthwhile investment to me.