I tend to go through bottom brackets quickly because I am about 215lbs and had a serious injury on my right leg a few years ago. I push much harder with my left leg so that after 3-5k miles i wear out my BB. I currently have SM-bb70 (part of the SLX group set) on my Bruce Gordon BLT.
My rookie questions are: Are bottom bracket sizes standard? In other words. When looking for a replacement do I need to measure the size of my BB 1st? Do you have a recommendation for a long lasting BB? I don't mind paying a bit more for a BB if it will last longer.

Thanks

if you can spring for the chris king with injection tool that would be the easiest from a maintenance perspective. i would also consider getting your bb shell faced

On the basis that we are only talking about HollowTech 2 External Bottom Brackets

Shimano HT BB2 Bottom Brackets are a standard design, and the fitting is interchangable with each other and other brands of HT2 BB's. The sizing is determined by the BB shell, this will be 68 or 73mm, the BB has spacers to compensate for this difference, and make sure that the fit is correct for the crank.

There is a difference between road and MTB BB's these are not interchangable.

You say you are getting 3-5k from a BB, that's good for a HT2 BB; dependant on conditions ridden in, if you want longer, would look at a Phil Woods, or when you BB70 fails, get the bearing pulled from it, and replaced with Enduro bearing. the shells normally don't wear out, just the bearings

Bottom brackets are the interface between the bike frame and the crankset. Since neither is really standardized, neither are bottom brackets.

Where it meets the frame the width, diameter and thread pitch have to match. Almost (but not quite) all bike bottom bracket shells are either 68mm or 73mm wide and English threaded.

Where it meets the crankset the spindle length and crank interface have to match. Spindle length is easily measured. The interface is going to be square taper, hollowtech, octalink, Isis, etc. There's lots of different ones.

Thanks for the replies. I am trying to understand what is being said here and looking up some of the terms on google. I am trying to learn about bike maintenance one step at a time.
I found https://www.cheapbikeparts360.com/pro...ottom-bracket/ based on Jim's recommendation. I cannot tell if it is for a MTB or a RB.
I am headed out to church and look forward to reading more about this when I get home.

Would give Phil Woods a mail to confirm with them https://www.philwood.com/support/faqs.php as to the compatibility with your Crank

I would assume that a Bruce Gordon bike's BB has been faced. The outboard BB's use radial bearings that aren't the best choice for our use. They aren't designed for lateral loads and with uneven pressure you may be putting more of a side load on the bearings.
Enduro has an external BB with cups and cones, but it comes with ceramic balls and is very expensive.
A crank that uses old square taper bottom brackets might be cheaper in the long run and more reliable.
This is a good one: https://www.bikeparts.com/search_resu...p?ID=BPC314973

The crank is a Deore LX triple but I cannot figure out which model it is.

Look for the model number on the back of the crank arms. It'll be something like FC-M580.

Ahh, thanks! it is FC-T661