Bicycle Mechanics - Old Tange cup and cone to new shimano un54 bottom bracket
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01-13-11, 08:34 PM
Is this a straight forward swap. Can I just get a un54 with the same length spindle and get the correct chainline and crack-chainstay clearance or is there more to it?
Essentially a drop in replacement.
As long as the spindle is the same length
the rest should be very close to the tange setup.
01-13-11, 09:54 PM
The only problem is if the original Tange spindle was asymmetric with an offset. If this is the case, then the UN54, being symmetric, will shift the crankset to the left relative to the Tange. If the offset is minimal, it may make no discernible difference. But if the offset is a few mm, that can be significant.
01-14-11, 01:57 PM
What SPB said. So a practical approach is to pull the drive side crank arm from the old BB, measure the spindle end to the cup, and make sure you get a cartridge that matches that key dimension. The non-drive side is less important, unless you care a lot about q-factor.
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