Camilo

I'm looking at buying a used bike with this bottom bracket: "Shimano Dura-Ace External Bearing"

The bike currently has a Dura Ace 7800 53-39 crankset on it, and I plan to change it to compact. A couple of questions:

Is this an easy DIY? Any special tools required? For what it's worth, back in the 70s and 89s, I knew how to remove the cotterless cranks on my bikes and maintain/rebuild the BBs, but haven't done any of this sort of work in the past 20 years.

I'm assuming I can stick with the same front derailleur. Is this true?

If so, will there be major front derailleur adjustment issues? I have competence with adjusting derailleurs, but haven't actually installed / positioned one in ages. I'm pretty sure I could do that though.

Exactly what sort of specs should I be looking at for the new crank? I know the number of teeth on the chain rings that I want, but nothing else.

Any other aftermarket brands cranks I should look for (FSA, SRAM, etc.)? I'd like to stick to close to the same level of quality and weight as the current crankset, but am not married to Dura Ace or Shimano. I'm an avid recreational rider but not very strong and don't race, mid-50s and about 165 lbs. I probably don't need the absolute most durable/strong crankset, but don't want to insult the frame and groupset with a bottom of the barrel crankset. I'd like to stay reasonably light weight if given options.

Thanks, as usual.

CACycling

I'd go with an Ultegra compact. Good, solid crankset and not too heavy. Not sure if the DA BB is the same as for Ultegra. If it isn't, Ultegra external bearing BBs can be had pretty cheap. As for what to look for, chainring size (which you mentioned) and crank arm length. Typically you'll see them in 170mm, 172.5mm and 175mm.

For the install, you'll need a tool to remove/install BB cups if the DA don't work with the new crankset, a tool to tighten the preload screw on the crankset (if you go Ultegra), allen wrenches to tighten the clamp bolts on the crank arm and allen wrenches to loosen/tighten the FD (yes, you'll need to lower your FD to work with the compact crankset). Not a huge job but you'll need the correct tools.

This is my choice for external BB removal/installation and it also tightens the preload screw:
https://www.nashbar.com/bikes/Product...2_10000_200497

operator

You forgot a chain tool, and a chain pin (unless he's using a quicklink).

OP: Do yourself a favour and stick with a shimano compact if the rest of your drivetrain is already shimano. Do not buy anything remotely resembling an FSA, especially anything named Gossamer. The bb's suck, the cranks suck. Same goes for sram for anything less than Red quality.

CACycling

+1 Forgot the chain tool and agree FSA is a brand to avoid.

HillRider

External bottom brackets are just cups with bearings and the spindle is part of the crank arms so the DA cups you have will work with any other Shimano Hollowtech II crank, either regular double or comppact and any group.

Shimano says their double front derailleurs wok with either regular or compact chainring.