Q about replaceable derailleur hangers

[joshatsilca]

The big change here is that modern thru-axle systems route all of the loads and forces in the derailleur hanger into the hub axle and thru-axle, so that the frame sees almost nothing in terms of bending loads on the hanger in the event of an impact. This is opposite of QR frames, where there is very little bending load handled by the axle and QR nut and a very high percentage of the forces are handled in the frame. So thru-axle designs allow us to make much, much stiffer hangers which will provide for improved shifting, and then as long as we allow for failure at a certain point, we can still protect everything else, mainly the derailleur in the heaviest impacts.

The hangers also plastically deform at more than triple force of the factory hangers, so for pro racing, the need for bike changes due to bent hangers from minor incidents and crashes is reduced significantly.

Essentially, the entire system has changed and the old rationale is no longer valid, but the desire of many manufacturers to continue using the cheapest, softest, crappiest, cast aluminum for hangers has remained.

[Carbonita]

Great explanation, per usual. I can't be the only geek here wanting to see an FEA sim or (even better!) an experimental test!

Originally Posted by joshatsilca

The big change here is
that modern thru-axle systems route all of the loads and forces in the derailleur hanger into the hub axle and thru-axle, so that the frame sees almost nothing in terms of bending loads on the hanger in the event of an impact. This is opposite of QR frames, where there is very little bending load handled by the axle and QR nut and a very high percentage of the forces are handled in the frame. So thru-axle designs allow us to make much, much stiffer hangers which will provide for improved shifting, and then as long as we allow for failure at a certain point, we can still protect everything else, mainly the derailleur in the heaviest impacts.

The hangers also plastically deform at more than triple force of the factory hangers, so for pro racing, the need for bike changes due to bent hangers from minor incidents and crashes is reduced significantly.

Essentially, the entire system has changed and the old rationale is no longer valid, but the desire of many manufacturers to continue using the cheapest, softest, crappiest, cast aluminum for hangers has remained.

[bahyow]

I'd be curious to hear Josh's take on how much variance there is in the 3d printed hangers. Coming out of the aerospace world, all the old curmudgeons (sometimes including myself) are concerned about process control and it's effects. With 3d printing there are additional processes, that in theory effect strength and toughness.