Bicycle Mechanics - Bottom Bracket Play?
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01-14-13, 07:06 AM
Overhauled the bottom bracket on my 1960's vintage French bike yesterday. Lots of problems caused by ameteurish work done previously, but that's another story. How tight should the axle be? The books I have are somewhat contradictory - "screw in adjustable cup all the way, then back off 1/8 turn", "slight play in the axle", "no play in the axle". Right now, it has very slight movement in the axle, back and forth and side to side. Too loose? Just right? The bottom brackets on the other bikes I have vary - some are rock solid, others also have slight movement. The bike is sitting on the stand now, so this is the time to make any adjustments!
01-14-13, 07:41 AM
ON a BB that is in good shape (no pits, uneven wear on surfaces) the proper adjustment is no play. The source that told you to back off the adjustable cup is dead wrong. When you tighten a BB lockring it pushes in against the BB shell and pulls out on the cup. All threads have some play in them, so the result is to make the adjustment looser, not tighter. Refer to parktool.com or sheldonbrown.com for proper adjustment. If a source does not refer to "preload" on a bearing you may not be getting full info.
01-14-13, 07:43 AM
If it's a cup-and-cone type bottom bracket it should be adjusted until there is no detectable play but it doesn't bind. It's a fine line and will probably take several trys to get it right. Cartridge bottom brackets are not adjustable and when the play gets noticable, it's replacement time.
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