Can anyone tell me why rear dummy axles for through axles come in both 20mm and 19mm diameters? I realize this dimension relates to the size of hub, but is one dimension more common than the other? It seems like 19mm is the standard. Yes, or no?
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I don’t think the dummy axle’s diameter is what is important, at least for non through axle designs. But 19mm is ever so under .75”, a very common stock raw material size, and about what a slight skim pass on the lathe might shave off. Now 20mm is a common metric country size. Lastly there’s the likelihood that the 19 and 20mms are not actual dimensions but labels of general reference. Andy.
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Take a look at the description of dummy axles on bikefabsupply’s website. They have a standard 20mm version for USA made dropouts and 19.25 version for some import dropouts. I have no idea why there is a difference, but I can confirm that the 20mm version is indeed ever so slightly too big for some dropouts, I had to file it down to fit Tange and Allotec.
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The larger size also obv won’t work with many of the disc brake fixturing systems.
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