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Old 12-22-18, 10:46 AM
aire díthrub
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Join Date: Sep 2017
Location: chatham-savannah
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Bikes: Raleigh Competition, Pashley Roadster Sovereign, Mercian Vincitore Speciale

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Something that I did not notice when I first built the bike nearly 3 years ago is that one side (the right side in the photo) is about 3mm longer than the left side. Unfortunately I don’t know for sure which way I had it installed, but I presume I had the short end on the drive side, the chain ring was very close to the stay (probably backwards??). Can anyone confirm which direction it should go? Will a symmetrical axle work for this application or should I find one like this?
traditionally, with an asymmetrical bb, the longer side is the drive side. These are most common on road cranks, to give extra clearence for the chainrings. They are also found on older proper track cranks as well though, depending on the design. Ideally all square taper cranks should be asymetrical. There should be no issue in flipping it around, to get the chainline more narrow. (A common trick with conversions on older frames.) the problem with doing that though, is it will cause your non drive side crank arm to be offset way out. This probably won’t affect your pedal stroke noticbly, but if you’re concerned with aesthetics, it can look pretty odd. Most modern square taper bb’s today only come symmetrical, obviously because different cranks require different offsets. If you’re going to switch from asymetrical to symmetrical, you have to take the offset into account, in your total length when converting, if you want the driveside crankarm to sit in the same place (chainline). The problem of course is that you can only take one side into account. That means one side will either be inboard or outboard from what it was designed to be.

Last edited by seamuis; 12-22-18 at 11:26 AM.
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