ISCG old or ISCG 05?


Turbo Monkey
Nov 28, 2005
Spreckels, CA
What's the deal with this? Did most bike companies not go for the iscg 05 standard, or is it only a few companies like moorewood?


Jul 18, 2006
Above you on the podium.
Not that this has anything to do with the topic, but what was the point of switching from iscg to iscg-05?
Was it an issue of addapting to bike design, or just something new?
I cant see any perfrormance increases with the new design....


Turbo Monkey
May 14, 2006
It is my understanding that all the ISCG-old standard did was specify the distance between the holes. This was somewhat loose and you'd often get bikes/chainguide problems as a result. With multiple bb's now being used as well, the ISCG standard was somewhat dated.

ISCG05 takes it to the next step to define more accurately where these holes are, the depth, and positioning of other members around it.

I think its main goal was to make a system such that the chainguide manuf could properly make a chainguide and not have to worry about computability with a frame.

from iscg05.com

1. The ISCG 05 is compatible with all currently available bottom bracket types that we are aware of. Drawings are provided for standard, BMX, and ISIS Overdrive designs. The new ISCG 05 is broad enough in its scope that other types may be integrated in the future. This addition offers simplified chainguide installation for shops and consumers and aims to cut down on chainguide model variations industry wide.

2. The new ISCG 05 standard tab clocking is now defined in relation to an imaginary line running from the center of the bottom bracket shell to the center of the rear wheel. This clocking method is identical to that used with conventional derailleurs. This aims to eliminate the guesswork that plagued the past standard. Big thanks to James Gardner and Dan Connors at Cannondale for this well thought out addition to the standard.

3. A new rotated standard allows frame designers flexibility to use low non-elevated chainstays on long travel frames. This rotated standard uses the same bolt circle and relative positioning as the ISCG 05, repositioned 14 degrees counter-clockwise.

4. Tab thicknesses, tab offset, and tab parallelism to the bottom bracket face are now all defined simply and completely. This aims to eliminate the guesswork that previous ISCG users faced.

5. A new larger 73mm bolt circle diameter makes for more robust mounting. ISCG 05 frame tabs can be stronger than previous incarnations, and chainguide rotation is less possible.

6. Outside vendor supplied ISCG 05 adapter plates are now governed by a 2.5mm thick mounting width. This allows simplified setup for consumers using external cup bottom brackets like the Raceface X-Type and Shimano Saint. Big thanks to Bryn Johnson from Raceface for this forward thinking addition.