Originally Posted by
CliffordK
Found these rings for the Ultegra 6800.
https://absoluteblack.cc/oval-road-c...for-110-4bcd/#
30/46 & 32/48.
Reading the page, they are doing several optimizations. First of all, the Ultegra 4 bolts aren't oriented on a square, but rather on a rectangle. That allows an oval ring to be used that fits onto the bolt holes better.
Second, they're adding an extra spacer, spacing the small rings off of the spider, and I assume the large ring overhangs slightly to compensate.
Third, they use special bolts. 7mm for the 32, and a mix of 5mm and 7mm for the 30.
That's really interesting. I looked at my Ultegra crank and thought "no way?!"
It appears they move the chain line in a little, use special bolts, and just barely clear the chain plates on the small chainring mount points.
From the description:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
IMPORTANT
Due to very special
2.5mm offset construction of BOTH chainrings towards the frame and custom bolts:
*30T can only work with 46T and special bolt set 46/30. (bolts included with small ring)
*32T can only work with 48T and special bolt set 48/32. (bolts included with small ring)*No other combination or mix of rings will work. Due to special mounting construction, aesthetic bolt covers are not offered for this design
*
We Only recommend Dura-ace 11spd chain or Sram Eagle 12spd chain for proper clearance of mounting tabs
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Two normal bolts, two smaller bolts! This works with the ovalized ring.
It's bolted from the outside. Stock Ultegra is bolted from the inside, without through holes to the outside of the big ring.
Ugly, but a cool hack.
Big ring from outside:
Big ring from inside:
....
Small ring:
A tiny bolt in this position, and minimal clearance!
