tjkoko

In rebuilding my 1993 Rockhopper's drive train, I have narrowed down the BB selection: the Shimano UN55 and the IRD QB55 or QB75 or QB95. Helpful comments would be welcome.

ThermionicScott 

My thoughts, in no particular order:

First off, that QB95 looks too pretty to hide inside a frame.

I'm using the 103mm QB55 in my fixed-gear and it has been doing the job for a couple thousand miles with no issues. Of course, I can say the same about any cartridge-bearing BB I've used to date.

The main benefit to the QB75 seems to be the aluminum cups, which drop the weight by a few grams (my 115mm and 118mm UN55s weigh something like 285-300g vs the 240g of the QB75) -- whether that's worth the extra $20 is up to you. I'm seeing a spec'd weight of 255g for the QB55, FWIW.

(Hmm, I could be saving ~50 grams at a rate of about a dollar each on my bikes...)

LlamaBikes

Shimano UN55's are known for lasting many 10's thousands of miles in all kinds of riding conditions. I have yet to kill one. I also have a QB55 in one of my bikes and it runs fine too, no problems whatsoever, although I haven't run it for many (10's of) thousands of miles yet to be sure.

The 10 year warranty on the QB95 is neat, although you could buy 4 UN55's for that price.

SquidPuppet

FYI the Shimano UN55s are asymmetrical. The NDS taper protrudes 2 ~ 3mms farther out than the DS. I don't know why they are built this way, but they are. This may or may not have adverse effects for your application.

I actually benefited from it. I have two goofy old single speed bikes with off centered BB shells and the UN55s allowed me to achieve a perfect chainline and a balanced Q factor.

ThermionicScott 

Not all of them!

Harris Cyclery measured the length from the BB shell to the end of the drive-side spindles on all of the Shimano BBs, plus the Tange 103mm unit. I did a little more math to figure out the remaining NDS length and determine whether they were within 1mm of being symmetrical, and saved the results in a table on my computer.

I'm guessing you were using the 110mm units, which are recommended for some cranks. So goofy, though...

tjkoko

The weight savings issue is, to me, a total non-issue. 8) I couldn't care less about a 50 gram deficit.

tjkoko

To me both brands of BBs appear to be of good quality based on the replies so far.

SquidPuppet

I didn't know that and thanks for providing the OP with clarity.

Yes I am using the 110. Man that is really wonky. Ranging from balanced to + DS to + NDS, anywhere from inconsequential to a significant amount. Koo koo.

Could it be QC or were your findings consistent with a number of units?

ThermionicScott 

I'm thinking that's just how they are. There might be a little variance in length depending on the machining, but I doubt it amounts to much.

The 110 always makes me scratch my head -- I wonder if there was a crank way back when that needed a spindle like this and it became its own standard. Usually, older cranks needed the extra length on the other side, though!

I use the symmetrical ones on my bike: 103mm, 107mm, and a 118 is going with a crank swap I'm about to do.

trailangel

IRD much better quality, hands down.
I have several of each, and I will never purchase another Shimano BB. They sit in the toolbox while the IRDs are mounted on the bikes.

SquidPuppet

It's funny actually. On my previous SS builds, the cranks I used called for 103mm BBs. I used a non Shimano brand which resulted in a super tight ultra precise fit to the shell. Super compact and I loved it.

The one bike I recently built up with a different brand crank called for a 110mm BB. I bought the Shimano this time around and when I got home and opened the box I was like, "What the hell is this? It's obvious to the naked eye that this is way off center. I call foul. This will ruin my chainline and my chain ring and arms may hit the stays. This is BS. Um, er, uh, wait a second, hey, I have this reversed in my head, this is actually going to correct my off center issue."

Straight drive train = Happy face.

ThermionicScott 

Haha, no sense in arguing with success!

Jeff Neese

I used a UN55 in my own Rockhopper and am very happy with it.

ThermionicScott 

This thread caused me to investigate my options while I have a bike torn apart and now a Tange LN-7922 (hollow spindle, aluminum cups) is on the way. I already had a UN55 in the right length, but...

arex

UN55's are hard to beat. I'm currently rebuilding my 25-y/o MTB commuter and had planned on replacing the BB, but when I took everything apart, I found the old UN55 spun just as well as the new one I bought. I went ahead and put the old one back on.

InTheAether

I bought a new UN55 off wiggle.com for less than $20 last month. It cam with Al cups and hasn't creaked once since I installed it. It certainly seems the business for the money.