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Bottom Bracket Replacement
#1
Previous Post was wrong.........
My bike is currently using a shimano BB-UN72 110mm. Its time to replace it, but can't find a match anywhere to purchase it. Is there a different number i can get to work with my set up?
Crankset - Shimano FC-M440 Crankset 175mm 44/32/22
Any suggestion would be greatly appreciated!
Nathan

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#2
OK, what you need to know is what thread type your frame is. From what you say im 99% sure that yours is british thread type 1.370x24 , there are two widths of b.bracket shell with the british type. 68mm and 73mm you need to know this too. You have your axle length (110mm), alright yeah. Now what type of axle, there are a few but you likely have a square taper axle. Once u have this info you can use any brand of b.bracket but I would stick with shimano. removing the old one can be tough if its been in there a while and the drive (chain) side is cross (backwards) threaded (with the british type). All in all nathan this is a complicated job and unless you're dead set on doing it I would leave it to the bike shop. At least the first time so they can Id exactly what type you need. Y'know what I mean son.

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#3
You can use use any of the Shimano UN series bottom brackets.
Such as UN26, 53, 54, 72, 73, etc.
Generally the higher the number then the higher the quality.
You have the main dimension (110) and, as Chainbrain says, you need to know the bottom bracket width (68 or 73). (There is a third size - 70mm - but this is the Italian type and you are very unlikely to have this)
Two ways of determining the size =
1) There is usually a label on the cartridge that states 110 x 68 (maybe 68x110).
2) Measure across the BB shell in millimetres.
To change the BB is quite straight forward (as long as no one has used threadloc) but you do need the correct tools.
"Crank Puller" and "Cartridge tool".
See: http://bicycletutor.com/cartridge-bottom-bracket/
But remember the drive side is "left hand threaded"

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#4
Great info gents!

Thanks. I found all the numbers you mentioned, except one.

The BB shell. I didn't know what that was. I assumed it was a measurement taken on the BB device itself.

When I searched for it online, I found it's a measurement on the frame of the bike.

Just thought I'd add that. If an old, rider like me doesn't know that, then maybe others don't as well.

This will help me completely replace my drive train! First time ever. I'm psyched.

Thanks again for the great info.
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