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Dent near bottom bracket on vintage steel frame

Bicycles Asked on July 19, 2021

I just bought myself an old vintage Koga Miyata and just realized today that there’s a weird dent on the frame near bottom bracket.

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Is this something I should be worried about? Or is it normal with these kind of frames, and what’s it for?

EDIT judging from other pics of the same frameset it seems like it’s normal? https://www.velosaloon.com/products/koga-miyata-gents-touring-frame-in-58-5-cm-c-t-57-cm-c-c-with-high-tensile-1024-tubing

Any idea what they are for and why aren’t they symmetrical?

One Answer

The chainstay has been crimped (at the time of manufacture) to provide extra clearance for the chain rings. On some bikes, I’ve seen this clearance provided by having the bottom-bracket end of the chainstay be a solid plate (thinner than the chainstay tube).

The bike almost certainly came with a multi-gear crankset when new.

Correct answer by RLH on July 19, 2021

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