Cant address your question, but I have a 07 or 06 version and it still rocks. I thought about making it a tri bike (don't have one right now), but not sure what to do with it. I am probably going to make it a trainer only bike for now. I thought about selling it, but not sure what to ask for.

Good luck!

Anyone?

What confuses you about an English threaded bottom bracket?

Some terminology confusion here.

Your frame has a BSA BB shell. This can't be upgraded. Well, maybe you can buy a different shell, but you'd need to know what alloy the frame is. You'd probably need some sort of credible plan to shorten the seat and down tubes to fit the bigger diameter shell, so figure some framebuilding tools. You'd need to weld the shell, then heat treat the frame. This will destroy the paint, so you'd need to repaint the bike (and I think strip the paint before heat treatment, but not sure - I've never done this myself). FYI: aluminum bikes can theoretically be welded, but it's not economical to do so.

BSA is 'old', but it's still a serviceable standard. Grand Tours have been won on cranksets with 24mm spindles, which fit fine in a BSA shell. Alternatively, some credible BB companies (e.g. Chris King, Kogel) make BBs for BSA shells and 30mm crank spindles (or the 28.99mm DUB spindles).

You didn't specify what groupset you're looking at. If you're sticking with the groupset's cranks, you just get a BSA BB that accommodates the crank's spindle. If Campy, you're getting BB cups rather than a BB, because they have the bearings attached to the cranks, but maybe that's just semantics. If you are getting a 3rd party crank, like Rotor or Easton, you match the BB to the crank's spindle. With Easton, that's 30mm.

You can stick any crank made by a major manufacturer in that frame. You can stick a wide variety of BBs in that frame. You didn't give us any sense of your preferences, goals, or what you're looking for. So the question is too broad. I could just pick a random crank, but that would be doing you a disservice.

I have a road bike thats I believe a 2006 Specialized Allez Sport that someone built up with full 2014 Tiagra 4800 group set including the crank set. Its a fun bike I love riding it. I'm not a bike mechanic, but if it helps, the BB says "SM-BB52 MOUNTAIN" on it.

Just curious why upgrade? If its a 2005 with 105 9 speed I'd say just clean, lube and tune it up and go rip it up:)

It's crazy that someone would put a mountain bottom bracket on a road bike.

Yeah I just noticed it for the first time, so functionally would there be any difference in bearings? or is there a size difference?

The bearing seals were designed for a mountain bike to keep mud and water out, so they would have more friction.

Ok interesting, I just bought my first power meter so very curious to do some of my regular rides and see how much effort is going in.

The seals maybe increase friction by 0.25 watt.

68mm BSA is not that old and definitely not obsolete. shimano hollowtech II cranks and bottom brackets will fit just fine, same with most SRAM GXP or whatever it's called these days. The crank you have is probably just fine, but if you want to upgrade, just find a new bottom bracket with british threads.

Right. The majority of the friction isn't from the bearings themselves but the seals, grease, and the quality from the manufacturing tolerances of the assembly. That's the summary.

This article does a great job going into depth, and touches on MTB and Track bearings and how they differ from Road:

https://fitwerx.com/...ycles-which-is-best/