Shimano BB
 

I am very pleased, my cranks were stuck after not being maintained by the previous owners on a regular basis. Now that I am saving over a hundred for a new crankset all I need is a bottom bracket. Now I am alittle torn between what BB to get. Shimano has the UN5x, UN7x, and UN9x. What would be the best? I read that as long as you go between one of those 3 you will be good to go, but would it be worth it to get the UN91 as its about as good as it gets and its only 30-40 bucks?

Even the UN-53's are fine, they're LX / shimano 105 level bb's.

I've never found a reason to get fancier than the un-53.

Have you heard anything about IRD QB-55 or Tange LN39 bottom brackets? They say for the price they surpass Shimano.

What the hell price would that be? The UN-53's can be had for $22USD. And that's not even looking very hard.

all 3 are made by tange.

really is hard to go wrong with a un53 i have had a couple go south on me in a year or so but also had some that seem to last just about forever.

i'd say the only reason to go for something more expensive is if your looking to save some weight or if you need a dead reliable bike for a trip across continental asia or some such nonsense. and then i'd still only really trust shimano or the ridiculously expensive phil wood. i am sure other companies make good bb's but i don't have any experience with them.

the plastic side of the un-53 can be destroyed very easily if you let a ham-fisted shop employee work on your bike

so on second thought, just don't let any inept wrenches touch your bike and get whatever your budget allows.

+1 on this comment.

The plastic non-drive side cup on the 53 blows. That and the drive side is steel, and the spindle is not near as nice as the 73 or 93. On the UN73 both the drive and non-drive side cups are aluminum, the spindle is nicely machined silver hollow cro-mo rather than black pot-metal solid (not hollow) steel on the 53. The bearings however I believe to be the same (at least I could never tell the diff). Lastly, the 73/93 BB shell is cut away a bit to save weight. If it were me I would get the 73 (I have used about 5-6 of them over the years) and they have been without flaw.

The only reason to get the UN-9x over the UN-73 is if you need a 103mm bb spindle. Old Dura Ace was the only Shimano BB that had a spindle that short. The UN-7X never came in any size less than 107 to my knowledge.

Last, not to be a complete self serving a$$ but I have a NOS UN-73 68x107 BB I could sell you if you are interested. Would sell it to you for about the same as you could get the 53 for. I think I may even have new 8mm crank bolts I could throw in.

I just bought one at my LBS and the non-drive side is plastic.

Hm, perhaps I have a UN-72 because both drive and non-drive on mine are black annodized aluminum. I know when I worked at a bike shop we used to swap parts with other inventory to make an item whole. If it did not come in a box and was just the bare BB, they may have taken the non-drive cup for another BB. I have never seen a un-72/3 with a plastic cup but it has been a while since I worked at the shop too.

72/73 usually comes with alu cups

I got a UN54, pretty sure I remember both cups being aluminum when I installed them... not positive though.