Here are two frames: Velo Orange Campeur and New Albion Drake. Assume that they are made of essentially the same steel, 4130 CrMo. The Drake has a very pronounced dimple on the inside, to help increase tire clearance. The Campeur, as far as I can tell, has no such dimple, so let's assume that the Campeur chainstay is entirely dimple-free, inside or out. Other things equal, would this difference make the Drake a weaker frame?

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    As all things are not equal I fail to see how an answer to the question is useful. – mattnz Jul 12 at 0:15
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    Either frame will be fit for purpose of being a bike frame. Neither frame will be endangered by this design. Make your decision based on something tangible, like tyre clearance and perceived comfort to the rider. I don't think this question can be answered outside of opinion and conjecture, or perhaps destructive testing. – Criggie Jul 12 at 5:02

The dimpled chainstay may have less stiffness in certain directions at that point, but if forces are not concentrated there, or in the direction of less stiffness it just doesn't matter.

A u-shaped beam (which is what the heavily dimpled tube essentially is) has less resistance to twisting forces than a tube, but there isn't any significant twisting forces on the stays.

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    It's also worth pointing out that in some cases, "less stiffness" is what designers are actually after, especially in stays, as a way to build in some minor suspension-like give in a frame. – dwizum Jul 12 at 13:33
  • Also, the chain-stays are only ever loaded on tension. You push the bike down at the seat and the bottom bracket, and the stays provide the counter force. This counter force is pressure for the seat-stays, and tension for the chain-stays. Of course, the bend in the chain-stays means that you get some localized bending forces there, but the overall action on the chain-stays is just trying to stretch them out. You could basically replace them with wires and still have a robust bike... – cmaster Jul 13 at 8:00
  • Over bumps and under acceleration that is not true. Also, chain stays need to have lateral stiffness. – Argenti Apparatus Jul 13 at 11:22

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