bottom bracket issue

[John-Ellis]

Hi Guys and Girls,

I posted before that my crank arms had a bit of a wobble, I thought I fixed this problem but by tightening the bolts. However the crank arms after a while started to wobble again.

Now the noises, creaks and wobbles is all unbearable. So I went to Halfords and got the tools to remove the crank arms and the bottom bracket.

All went pretty well until it come to the bottom bracket, it is not like modern bottom brackets the bearings and spindle are not housed in a cartridge assembly, it turns out my bike has the old fashioned spindle and bearing cup at each end with ball bearings inside each cup.

Now the bearings had grit and allsorts of dirt in them, so I took them out altogether and cleaned them, then I cleaned where they sit in the bike.

So my question now is, do I try and put the old bearings back in, or does anyone think I might be able to buy a more modern cartridge type bearing and spindle assembly.

Thanks

John

 

[fossyant]

Just go and get a shimano UN54 cartridge bearing BB. Fit and forget.

Assuming your existing crankset is shimano then the above is ok just measure the axel width and order similar. Frame BB shell is usually 68mm for road bikes and 73mm for MTBs so just measure this too

 

[John-Ellis]

See pictures of the spindle and bearings, you can see hoe dirty the bearings were.

 

[Rickshaw Phil]

Yes, a cup and cone type bottom bracket can be replaced with a more modern cartridge type. I presume it's a square taper type? (edit: didn't see your pics until after I posted) As Fossyant says, you'll need to know the axle length and the width of the bottom bracket shell (most commonly 68mm).

If you want to keep the bike on the road until you have the new part it'll be fine to grease and reassemble the old BB for the time being.

A question occurs to me: You state that you initially cured the wobble by tightening the crank bolts. Was the movement in the BB or the were the cranks wobbling on the axle? If the latter, the tapers in the cranks may have been damaged by being ridden loose and you may need replacements.

 

[John-Ellis]

To be honest until I get the bike back together I wont be sure what was causing the issue as all the bolts and tne crank arms were really tight. I did notice a lot of movement on the spindle though so I have a strong suspicion it was that.

But if it is being replaced im not too worried.

Thanks for all the help peeps.

John

 

[John-Ellis]

So what is the difference between say a un24 and a un54 bearing unit, they all seem to be 68/113mm in size?

Cheers

 

[Steve Malkin]

Your photo shows the spindle is stamped with a '3P' size code.
According to Sheldon Browns bottom bracket size database that means it is for a 68mm width shell and is an asymmetric one with an overall length of 119mm.
The symmetric equivalent would be 122mm in width, so the appropriate shimano cartridge would be a 68x122.5 BB-UN55 available from Chain Reaction cycles for £16.99 here:
http://www.chainreactioncycles.com/Models.aspx?ModelID=71369&_$ja=tsid:46412|cgn:Shimano - Bottom Brackets|cn:Chain Reaction-UK-PLA-PLA-All-DT-SE|kw:271963UK_UN55 Square Taper Bottom Bracket&gclid=CIHA-JKEjLgCFSXItAodcWIAwg

 

[Steve Malkin]

UN24 Vs UN54 is just to do with the quality of the bearings, basically the higher the number the better quality the bearing and the longer it should last.
If its just for a cheap hack bike then the cheapest one will do you OK

 

[John-Ellis]

Steve, I cant tell you how much I appreciate that mate, thankyou, I will place the order now.

Thanks again mate.

John