OK, it's been about 6 years or so since I mucked around with b-brackets and they've changed things around a bit.

I'm contemplating a new Chinese carbon road frame (Carbonal Talia) and I have a choice of b-bracket shell widths BB30 or BB86. I understand the BB30 is 68mm wide and uses a press fit b-bracket.

My question is, can I re-use my existing 7 year old Shimano Ultegra Hollowtech style crank - 54/30, and just buy XX brand BB30 bottom bracket ?. I even have a Park headset press to install, just not sure if I need a new crank or not.

As comment, the changes to bottom bracket designs is just friggin baffling and I've no clue why and how it got so confusing.

so you have not ordered this Yet so cannot actualy measure things in front of you

Your need and adapter if attempting to use a Shimano crank in a BB30 shell, like this BB30 Adapter for 24mm Spindle Cranks (Shimano, FSA, etc.) other brands are available.

Guessing you meant Hollowtech II (HT2), as Hollowtech cranks haven't been been made since the early 2000's and were all Octalink

For a guide on current BB standards, have a look at this Bottom Bracket Standards - Park Tool

Or....just shop for a different cheapo Chinese frameset that comes with BSA and none of the pressfit-idiocy.

Pressfit like BB30 and BB90 and BB86 all came about because manufacturers wanted to save money-as molding a whole is cheaper than making a threaded insert and making it work well....problem-by trying to do things cheaper for themselves the results are underwhelmingly annoying to the consumer due to lack of necessary engineering precision IRL and PressFit only working really well inside CAD where everything fits perfectly together. PF is a cost cutting measure, it really gets the consumer nothing but a ton of engineering-marketing talking points and headaches due to noise.

Yup, the b-bracket on the bike says "1.37 x 24" so a 24mm spindle crank.

Marcus has a good point about finding a different frame, trouble is all the cheapy Chinese frames I'm seeing use PF or assorted shell widths.

I'll keep looking.

BB86 will work with your Shimano crank - assuming it is a 2 piece, 24mm spindle crank.
BB30 will work with adapters.

A thanks for the links, especially the Park site. I love the Park site.

The more I read, the more I shy away from any press in system. Seems if you don't get it correct, the bearings fail early (too tight) or the system creaks (too loose), or you get lucky and it's Ok. I can see where it's OK for somebody installing frequently, but for somebody doing this every couple of years ?, big PITA.

I'm now hunting for BSA, 68mm shell, threaded.

Or I may just save up and buy an Ultegra 11spd. Di2 bike.

Thanks to all, it's much clearer now.