I am pretty sure that the bottom bracket is English threaded.

I would recommend buying a complete new bike.

Looks like 10 speed already (which I doubt was standard).
Check the wheels to make sure they're 11-speed compatible, if that's the way you want to go. And add 11-speed shifters to the list if you do.
Otherwise (if you keep it 10- speed) make sure you find a suitable 10-speed rear derailleur (not Tiagra 4700 which uses a different cable pull ratio to 10-speed 105/Ultegra/D-Ace).

The BB currently there is a square taper, but replacements are cheap. It will be an English threaded 68mm item, just get whatever matches your crank of choice (which should also suit how many rear gears it has).

Also add a chain, cables and bartape to your shopping cart.

The crankset looks like 105SC triple crank (probably an FC-1057), which came into being some time in the early 90s. It's possible that the bar-end shifters were added later specifically to facilitate an easy 10-speed conversion; Shimano didn't start making 10-speed drivetrain components until 2003.

The bike has a square-taper bottom bracket that's made to fit a 68mm-wide BSA (english-threaded) bottom bracket shell.

Hard to say much more without seeing more of the bike.

As far as giving recommendations, what are you trying to achieve? What do you dislike about the bike that you want to address?

Unless the parts are clearly worn out this is going to be a bit of effort for little in the way of performance gains. At the same time if the parts are clearly worn I probably would make some changes rather than replace like-for-like.

As others have mentioned you have a square taper BB and this style tends to wear with the cranks if they aren't maintained religiously so I would expect to have to switch them both. I would go with a more modern design like Tiagra cranks and BB assuming the frame does have a standard English thread. I 'think' your bar end triple shifter will work with a double if you get the limiter screws set correctly as its a friction design but you may also be looking a new front mech and new bar end shifter if you go double.

I have worn out brakes and had a lever fall apart but I would only replace them if they are truly shot.

In general my upgrade list after buying a bike would look something like:
Saddle
Bars (in combo with stem to get the front end right)
Seatpost (specifically if the seat post is a PIA to adjust)
Hydration setup

Overall your list looks like a mechanics safety checklist in reverse order. The parts need to work but its not where you will get bang for your buck,

The OP's photos look like the BB is probably a cartridge, and there's no maintenance that can be done on those. You just replace them when they're toast. But they usually last a very long time.
If it's still spinning smoothly, I'd only replace it if I got new cranks that needed a different spindle length or BB type.

A new front bar-end shifter wouldn't make sense unless the old one lacks sufficient cable pull, which would be very unlikely in a triple-to-double conversion.

Thanks for the replies, guys. The bike is currently in a bike bag at a friends house, while I'm in the process of moving. It hasn't been ridden in over a year, but here's a little more history of it. The previous owner put the bar end shifters on it; I'm pretty sure they're Dura Ace 10sp (I'll double check and take some more pics in the next few days). When I got it (about 3 years ago), I got new wheels (Mavic Kysrium Equippe S), seatpost, and handlebars. While it was moved/in storage, the rear derailleur got damaged. So it has to be replaced for sure. So I was thinking I'd go on and replace the front derailleur and the crankset while I was at it to make it more modern/streamlined/matching.

Shimano bar end shifters are only made as Dura-Ace.

Here is the reality- for most of us that are not going to Kona or racing in the pro tour circuit, a 90’s bike should be fine. A little story for ya, I setup my girlfriends steel Trek with Shimano 600 components to fit me. When I would fly to see her, I was using her bike for my long rides when training for Ironman back in 2013. The bike road great. Never an issue. I had close to a couple century rides on it too.

Reality also is that since the 9 speed revelations in bike technology, there has been little major advancements except for Di2 electronic shifting and hydro disc brakes, if those are things that interest you. 9 speed parts were introduced I think around 1998. It offered STI shifting built into the brake levers, hollow spindle bottom brackets to save weight, and dual pivot brakes. Those were major breakthroughs. Adding 10 from 9 and 11 from 10 on the cassette range is minor at best. So, if you already have a 9 or 10 speed groupo, just ride it. It’s a can of worms if you try upgrading stuff.

Buy an entire bike if you want to upgrade at some point. It’s kinda like putting money into a 2000 Honda Accord with 250k miles on it when a newer accord is going to make so much more sense.

8-speed SL-BS64 levers are considered an "Ultegra" part.


Shimano launched their first nine-speed road group in 1996. But I'm not sure I so much significance in that launch.

Integrated shifting was a big deal, but it came to Dura Ace 7400 in 1990, six years earlier.

Shimano's dual-pivot brakes were also introduced prior to nine-speed, for instance the BR-7403 from the early 90s.
Shimano's dual-pivots also weren't the first dual-pivot sidepull calipers, just the first to really take off. The earliest that I'm aware of are Altenburger Synchron brakes, from (I think) the late 1960s.
And dual-pivot calipers in general go back even farther, since the centerpulls popularized in the mid century were dual-pivot. The better ones are actually pretty darn good brakes, albeit less convenient to cable up than sidepulls. Single-pivot brakes possibly wouldn't have made a resurgence to popularity if it weren't for Campagnolo choosing them for their first brakes.

Splined three-piece BBs triggered a design revolution (and a standards war), but I'm not sure that their immediate benefit was very earth-shattering. Octalink cartridges aren't that much lighter than square-taper cartridges of similar purpose and price, maybe a few tens of grams or less. The spindle can be stiffer, but there's not much evidence that square taper flex is a problem in the first place.

I forgot about the SL-BS64.

I believe that they are not labeled with Dura-Ace or Ultegra.

They're labelled as explicitly non-Dura-Ace. :D



"Not compatible with Dura-Ace rear derailleur"

Thanks for the more detailed info

I think we are saying the same thing. Not major improvements, to some degree. Square taper always worked fine for me. Funny how the 2 piece crank (spindle attaches to drive side arm) became the standard by most and Bullseye was doing that on BMX cranks in the 80’s. Nothing new there either. Moreover, thru axle becoming popular and QR skewers always seemed to be fine as well.

His bike is fine. It’s more about the desire to want something new.