No, really. What does it designate, since Shimano's own web is cryptic on this.

HT were the hollow crankarms, HTII was supposed to be hollow spindles and Hollowglide are the chainrings.

So any hollow spindle should be HTII, i.e. all 2-piece cranksets should be HTII as per:
https://bike.shimano.com/en-EU/techn...lowtech-2.html

But then in Shimano specs:
https://productinfo.shimano.com/#/spec/ROAD/Crankset

So 57xx is HTII, but 47xx is not? It's a 2 piece crankset ...

If you look at the 4700 cranksets, they are cast with C-Channel on the back.



The 105 cranks R7000, are hollow forged. The Ultegra/Dura Ace cranks are hollow bonded. Thus, they essentially have a hollow tube.

Ultegra/Dura Ace, Hollow Bonded

105 Hollow Forged

I know I know, there was the other discussion about failing hollow bonded crankarms (not mine), then I started the one on hollow chainrings. But the Shimano web is adamant about specifically HTII: "HOLLOWTECH technology is an ultra-lightweight hollow crankarm created by SHIMANO with the company’s own proprietary forging technology that also maintains rigidity. The addition of HOLLOWTECH II technology integrates the bottom bracket axle with the right crankarm for more stiffness and a weight savings to achieve a high-dimensional balance."

Then it goes on lengths talking about ... what is essentially every 2-piece crankset BB design and the hollow tube spindle. So that HTII is basically nonsense, has nothing to do with BB and in fact any Hollowtech (I) crankset is automatically HTII as well?

Just want to add, the reason I ask is about Shimano's markings on corresponding BBs.

Looking at R9100 they would label it (it's also on the packagaing like this) as HTII:
https://bike.shimano.com/en-EU/produ.../BB-R9100.html

Same goes for Ultegra/105 respective BB, also as HTII:
https://bike.shimano.com/en-EU/produ.../SM-BBR60.html

Even the Tiagra/Sora BB-RS500 say it's Hollowtech II:
https://bike.shimano.com/en-EU/produ.../BB-RS500.html

Then on Tiagra crankset they only list the logo for "2-piece crankset":
https://bike.shimano.com/en-EU/produ...0/FC-4700.html

Now apparently all those BBs above will work with all of Shimano's 2-piece crankset spindles, while everyone refers to all those cups across all lineups as HTII.

Big Marketing Names?

A lot of bottom brackets were largely hollow. Campagnolo Record/Nuovo Record square taper bottom brackets were hollow.

Octalink, and ISIS bottom brackets are hollow.

And, every 24mm and 30mm "two-piece" crankset with external bearings bottom bracket is hollow.

I think Shimano would have gotten into trouble had they called their Tiagra C-Channel cranks "Hollow". Plus they want something easy to differentiate their upper tier products from their lower tier products.

Right, so basically they got the HTII for marketing purposes originally, meanwhile all cranksets become hollow spindle, but they call them "2-piece-crankset" instead, but then forgot to put that logo on the RS500 BB even though it's the matching one for Tiagra/Sora.

Did I get it right?

"HOLLOWTECH" is registered as Shimano TRADEMARK
"2-piece crankset" is NOT registered as Shimano trademark, and it is used by other companies:

22mm axle "2-piece crankset" from Haro - https://jrbicycles.com/products/prem...piece-crankset
24mm axle "2-piece crankset" from Box - https://boxcomponents.com/products/b...35349237235879

This is why they don't advertise "2-piece crankset" on bb box
But, you can still find "2-piece crankset" label on bb tools:

This may well be technology and terminology that morphs over time.

Hollowtech was Shimano's big thing with the Octalink.
Then with the external bottom brackets, they would have introduced the 24mm 2 piece cranksets with "Hollowtech II". Initially these would have been exclusively Dura Ace and Ultegra.

I know that Claris got Octalink V2, which was used for several years.

When was the Tiagra 2-piece introduced? I presume the Hollowtech II had been in use several years before the Tiagra was converted to that technology (without the hollow).

I had Tiagra 4500 once and that was already 2-piece, feels ancient now but the design was retained for a while until the 4-arm FCs came ...

EDIT: Forgot to mention the most important ... bike it came on from 2008

2007 catalog:

Announcements:Descriptions (Hollowtech vs Hollowtech ii):Specs:

This is so cool ... so page 3 (as ordered above, marked 134) goes on to say the bold new cap-free* design is to *integrate* the spindle into the crankarm ... which they did ... in Tiagra 4500 then ... but it's 2022 and it is not HTII.