another Cycle Maintenance Q

Feb 27, 2009 7 Replies
R

Have asked on rec.cycling .... but also trying here.



Following on from earlier post on Bottom Bracket. (and loads of help)



Removed the cranks and stripped out the Bottom Bracket, it's all now de-greased & cleaned ... before I re-assemble ... a Q?



The bracket consists of a spindle shaft, a fixed cup on chain side and adjustable cup on other. Each cup has a ball bearing cage with 9 ball bearings. There is also a plastic bellows between either end to keep things clean.



I read the Sheldon Brown web article on Bottom Brackets ... he advises consideration of discarding the cages, and instead putting in 11 loose bearings.

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it worth doing this on a 21 yr old bike ? ... or does the inevitable spindle wear make this pointless ? (read that spindle will have worn more than balls)



There are 2 thoughts ..



# I go ahead and do this ... cost is only for 22 1/4" balls (should be cheap enough)



# I put the existing 9 ball cages back in for now, and when the thing does wear out change it for a sealed cartridge BB ?



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V

I'd go straight for a cheap sealed bearing and be done with it.

Under a tenner on eBay, delivered. Example: eBay 230327409552

D
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H

Rick Hughes formulated the question :

The sealed bearing from the start. Usually the races where the balls run will also have some wear and neglect, the sealed cartridge overcomes both problems.

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R

one's same size .... overall length and end cap thread size will be key.

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F

My experience of caged ball bearing units for bottom bracket is rather poor. Where the cage is the weakest link and becomes distorted and finally breaks up. I also favour the idea of replacing the cage with the requisite number of balls. If more balls go in it also makes a stronger bearing.

On the other hand, if it's not broke, don't fix it.

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C

No :-) See Sheldon Brown's site on the subject.

You've got threads (British/ISO, French, Italian - yours are probably the former though), BB width (68 or 73mm, yours will probably be 68mm), axle length (depends on crank fitting), taper angle (Campag or JIS - yours will probably be JIS/Shimano).

Axle length is the one you're most likely to come unstuck with - use the same as you have now.

Shimano UN5x (currently 54) is a decent enough cartridge BB. It's what I'd use.

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C

In message , Clive George writes

With one small proviso, the existing axle might well be asymmetric in lengths outside the BB - the chainring side being longer than the plain crank side. Modern sealed bottom brackets seem to generally have symmetrically long axles each side, so the overall length may need to be longer to allow for enough length on the chainset side.

I'd suggest taking the old bottom bracket bits into a bike shop which would mean you would get the right sized one (I'd measure the BB shell width as well, but most likely as you say to be 68mm)

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