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Bottom bracket
#1
hello,
Can anyone tell me how tight the bottom bracket should be?
Is it similar to the tightness when tightening cones (hand tight} ?
Phil.

And also when refitting the rear sprocket, how tight does it have to be? and does it self tighten?
thank you phil
  Reply
#2
What sort of bottom bracket is it?

Most newer bottom brackets are cartridge type, whether they are square taper, ISIS or Octalink. There are also external bottom bracket types like Shimano Hollowtech. None of these require any bearing adjustment, just fitting into the bottom bracket shell.

Older square taper bottom brackets, like the top one in this picture require adjusting:

[Image: bbs.JPG]

First install the bearings with plenty of grease in the right side cup (chain side) and install and tighten it in the bottom bracket shell. Then install the axle, then install the bearings in the left cup, fit it over the axle and thread it into the the left side of the bottom bracket shell. Lastly you need to fit the lock ring over the 4 or 5mm of protruding left hand cup thread.

Turn the left hand cup so that axle is free, but there's no play, then tighten the lock ring and re-check. You will usually find that tightening the lockring had altered the bearing adjustment and that the axle is now either too tight, or that there is some play. Undo the lockring and either loosen or tighten the cup, just an eighth or a turn or so, re-tighten the lock ring and check the feel of the axle again. Sometimes you have to do this a few times and fiddle about a bit to get it just right.
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#3
mine is the top one...

i pretty much done what you said.. thank you for taking your time to give me a great answer... Thanks to the people on this site i have carried out quiet a few jobs successfully already.
Phil
  Reply
#4
No problem.

When it does wear out, you can replace it with a cartridge type bottom bracket, like a Shimano UN54: http://www.bikeradar.com/gear/category/components/bottom-bracket/product/un54-bottom-bracket-14172, a doddle to fit, no mucking about with lock rings, and last ages.
  Reply


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