Taper bottom bracket sizing
 

First, I apologize for not hanging this off of an old thread. I searched, found a good one and added my question. I was blocked. Hmmm. Perhaps we are not allowed to post to old threads?

Below was my question as I try to help a buddy get his old MTB back on the single track.

Yes, old thread but why create a new one. Helping get a buddies bike on the road and I have never ordered a replacement BB catridge.

Shimano square taper
BB-LP27. Unclear if the 27 is telling me something.
73 XI. 73mm diameter IIRC
BC 1.37 x 24 is thread...
I did not measure the overall spindle length as I thought my photos of the BB would tell me all I needed to know.
I did not look to see if it was symmetrical or asymmetrical. I assume asymmetrical because it was on a triple fitted old school hard tail mountain bike.
I have only found a 73 in a 118mm length...not even addressing whether the drive side protrudes more than the non drive side.

Advice welcome and needed so we can order a replacement.

How do I order to ensure the correct spindle length? Best mail order solution these days? I am an old timer as you can see from my join date.

Measure the spindle, or look up the spec for the specific crankset you’re using.

Don't assume anything.. measure the old BB and FIND OUT. at least you still have the old BB to measure... when it's not there is when the real fun begins, and having spare old BBs around to test fit becomes the norm.

Asking your own questions in the threads of others is called hijacking. Even though you think your question is the same as others, there will be nuances that apply only to you. And then it gets hard many times after your post to know whether responses are for you or for the OP or a previous person that replied.

Starting a new thread is always the right decision. If you think other threads have pertinent info in them, then just link to them in your thread and explain what you thought useful in them. If a particular reply in the thread, then you can link just that response.

An update.

Length is 113mm and BCD is 104/64. 9 Speed Shimano, 3 chain ring MTB. Appears to be symmetrical. No real way for a definitive measure of a cartridge unless I am looking at it the wrong way.

Any advice where to order a replacement would be appreciated.
https://cimg1.ibsrv.net/gimg/bikefor...6759bb2b8.jpeg

From Sheldon's site.
https://cimg6.ibsrv.net/gimg/bikefor...5e0b29045b.jpg

It is generally bad form to add to old dormant threads. You did the right thing creating a new one. I would much rather have new threads then dredging up old threads unless you have some really pertinent info that just has to be shared in that thread and is extremely related to the original topic and really couldn't go anywhere else without being completely silly and ridiculous but those are few and far between.

In terms of this your crank will determine what BB you need generally so I would check the spec there.

In your case your local shop will be able to get you the correct B.B. and confirm data for you on the width but if the current BB was working in terms of length then just stick with the 113 in the correct width. However you can always bring them the B.B. to get the right one. If you are looking cheap the UN-300 is Shimano's only current choice but that means very little because your local shop might have some older 73mm B.B.s hanging around I know my second to last shop before my own had a bunch of them before closing in 2023 so you might find a higher end Shimano variant still. If nothing else Phil Wood, IRD Defiant/QB-95 or SKF make really good quality B.B.s.

Here's a link to an exploded view for the LP-27
https://www.google.com/url?sa=t&sour...ZQDgM3XcpB2KJK

As you can see, the only difference between the 68 & 73 is the LH cup.
Therefore, if you found a 68mm version, you could try to reuse the old, brittle, likely to break old cup.

Nothing more annoying than to pore through pages and pages of answers only to find out that the thread is many years old. If you want an answer to your question, start a new thread. Many people who suddenly realize that the thread is very old will not bother answering. Likely the thread you found was closed by the moderators. This often happens when people start arguing for no good reason

BCD, the number of speeds, or the number of chain rings are not part of the spec for a bottom bracket. You're not replacing anything else, right?

You've identified that it's a 73mm shell and length is 113mm. The 1.37 x 24 is the spec for English threaded (as opposed to French or Italian). There are a lot of options, but a Shimano BB-UN300 is probably the closest in general quality to what you're replacing. These are in millions of bicycles and are known to be reliable and easy to install.

Shimano BB-UN300 Bottom Bracket - English, 73 x 113mm Spindle, Square Taper JIS

FWIW: a Tange square taper bottom bracket is another option. Tange has a very good reputation for producing highly reliable products.

The Tange BB-3912 and BB-3922 currently appear to be available in 73x113mm from multiple online sources.