Super light, smooth shifts, dies quickly
- Familiarity: I've put it through the wringer
The XG-1099 is an impressive feat of engineering. This thing is significantly lighter than the XTR M980 10-speed cassette, and I feel confident in stating that it is probably the sexiest cassette ever made. The cogs on most cassettes are bolted to an aluminum spider or carrier. Here, all but the largest and smallest cogs are machined from a single block of steel and are thus connected to each other rather than being affixed to a central piece of metal. I've found that it shifts slightly better with SRAM derailleurs than with Shimano derailleurs, but I would happily use it on all of my bikes if not for the mayfly-like life span of the large cog.
Unlike the interconnected billet steel middle cogs, the largest cog (32t or 36t) is made of aluminum. I don't doubt that SRAM chose the aluminum to save weight in this weight-weenie's-wet-dream of a cassette, but the aluminum is much more malleable and wears out in an unacceptably short period of time. Worn out cogs can cause the chain to skip, shift poorly, or fail completely. Despite SRAM's representations to the contrary, this large aluminum cog is not replaceable. To clarify, perhaps the cog is theoretically replaceable, but SRAM has never released or sold the replacement cogs. I've worked on class actions that have been filed over less. A simple Google search will produce several forums and threads filled with rants from riders about how quickly the aluminum cog died on their $400 cassette, one chap claims his XG-1099 was only a few weeks old when it gave up the ghost as he power-shifted on a steep climb.
To summarize: If you are a racer who counts every gram, then buy this and put it on your race bike. It's awesome, but don't put it on your training bike and expect it to survive. If you are a weekend warrior who has the means and motive to spend $400 on a cassette, expect to spend another $400 in 4-6 months. Or just never shift to your big cog.