Bottom Brackets?

[simulatedjim]

I bought a Beast frame and fork, it is the Extreme Series.  The factory Bottom Bracket is Shimano BB-UN52, 110 mm spindle.  I've been reading about what the numbers mean but can't find this exact number to buy.  Does the "52" mean better quality? The higher this number the better? Will a BB-UN55 110mm work? 

[w2zero]

I have been meaning to look up some BB stuff.  Maybe this link will be of service to you.  http://sheldonbrown.com/bbsize.html

[simulatedjim]

Yes I found his site and it shows compatibility with some but skips over others which is what confused me.
CT21, LP27, UN40, UN51, UN52, UN71, UN72, UN91. the list shows these are compatible but the "55" is isn't? Trying to understand what the numbers mean.

[Scooter]

I believe the 55 has an aluminum adapter and the 52 has a plastic adapter.

[Colin]

Pretty sure the 55 is just a Quality/Year indicator.

higher first digit = better quality/lower weight

That's all I treat it as, anyone disagree?

Col.

[Neffro]

In my experience the higher the two digit number, the higher the quality. I have only used UN-XX as replacements and the are all decent, but the higher end ones weigh less. I am not sure how the bearings differ (or if they do). I think the 70's were equated to XT level and the 90's to XTR.

I do know that the low end LP-XX can be junk right out of the box. Some feel like there is sand in them when they're brand new and they weight as much as a small boat anchor.

[simulatedjim]

Everything I can find, agrees with what is stated above.  I got a UN-54 and it has a plastic half and the UN-55 has aluminum on both sides.(higher number)better parts.