Originally Posted by
am8117
Does anyone know if the previous 5-arm generation was also hollow, as in crankarms? Not the spindle - it's somewhat misleading to believe it's the bonding with spindle that is the culprit here, HTII has been around for a while before news of these started coming out.
Hollowtech has been around for quite some time. The Octalink (Ultegra 6500 and related) were called "Hollowtech II".
Based on the current notes, there seems to be a leap from "Hollow Forged" to "Hollow Bonded".
The older Octalink cranks were the Hollow Forged technology. And the ones that are failing are Hollow Bonded. The 105 (4 arm) and lower models are the Hollow Forged (or potentially solid in the lowest).
For weights of "new" sets (2018), I'm seeing:
https://ccache.cc/blogs/newsroom/201...ght-comparison
Dura Ace R9100, Cranks, 614g
Ultegra R8000, Cranks, 674g
105 R7000, Cranks, 713g
There isn't much weight savings with the Campgnolo carbon fiber cranksets.
So the 105 crankset is about 100 grams heavier than the Dura Ace, with the Ultegra somewhere in the middle.
The bonded cranks appear to have a cavernous internal space. And I can understand why Shimano chose that technology. However, the forged cranks seem to have more aluminum in the areas where more strength is needed.
Ultimately, if I move to the Shimano 4 bolt cranks, it may well be with the 105 which apparently is somewhat more robust (although it may depend a bit on how the spindle is formed and inserted).
Unfortunately I'm not seeing a list of which cranks had the bonded and which had the forged technology.
I have an Ultegra 10-speed, 6700 crankset, and for the life of me, I can't find any bonding marks on the crank arms or spider. So, I believe that has the previous technology of hollowtech forged.
The 6700 chainring, however, does appear to be bonded. However, the complaints I'm seeing are complaints about crank failures, and not chainring failures. In fact, the reviews of the hollow chainrings seem to be good, noting good weight to strength.
I don't have the Dura Ace 7800 crankset, but I think it may also be forged hollowtech (contemporary to the 6700, or slightly earlier). And, the chainrings appear to also be machined and not bonded.