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Q about replaceable derailleur hangers
I have nothing in my fleet with a replaceable derailleur hanger. (Everything is steel, brazed into the steel stays.) My understanding is hangers are in some sense "sacrificial." They break, not your expensive frame or derailleur. Am I more-or-less right about the rationale?
If so, I'm totally confused about an email I got from Silca touting titanium derailleur hangers. I can't get to the Silca site just now, but it's this URL: https://silca.cc/collections/derailleur-hanger Wouldn't replacing typical aluminum(?) derailleur hangers with titanium increase the odds that something much more precious is sacrificed in case of a crash or other unanticipated problem?
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Monti Special |
#2
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(probably should move this thread to General Forum) According to Josh Poertner, it's designed to fracture or deform before frame damage, but no test data has been provided.
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#3
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Unless the titanium derailleur hanger is made to fail, it wouldn't be a good idea. The only reason for the hanger to fail is to save the frame from expensive damage.
BTW, you can bend a steel dropout and bend it back. You absolutely can NOT do that if the aluminum, carbon or even titanium frame has the same damage.
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Forgive me for posting dumb stuff. Chris Little Rock, AR |
#4
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They make sense on carbon and AL bikes where bending and fatigue are an issue. I've had a few warp in the past on steel and Ti bikes and had the bike shop simply bend them back. I find them annoying really.
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#5
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UDH and T-type systems purport to improve the system. And Shimano has a competing patent, cuz, of course.
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#6
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I've gone through a few aluminum hangers on aluminum and carbon frames, they are pretty cheap, I try to keep a spare on hand for any bike I ride very much. They are "somewhat" tuneable with a hanger tool (I've never broken one truing it up) and toast after a significant bend, cracks or sheared off. All the steel frames I've ever had have steel hangers and I just true them up after an impact or "incident", they usually don't bend very much, the derailluer takes the hit instead of the hanger.
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#7
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Purport to lock you into buying $600 cassettes.
It'll be interesting to see how this shakes out or if the bike industry rejects SRAM's attempt to vertically integrate into all proprietary components while doubling the price on consumables. Last edited by rice rocket; 05-01-2024 at 11:25 PM. |
#8
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So it might be risky in damaging the frame but that hasnt been the case, a hanger cracking and turning the derailleur into a pretzel is also a risk. |
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#10
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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. |
#11
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Great explanation, per usual. I can't be the only geek here wanting to see an FEA sim or (even better!) an experimental test!
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#12
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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.
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