[Mark McM]

Originally Posted by yinzerniner

I'm sure there was a pretty big business decision to go to the XDr hub design instead of just sticking with 11 as the smallest sprocket. They probably could have accomplished the exact same goals in terms of drivetrain efficiency, cadence and range but it would have been more expensive on the manufacturing side since they'd have to make larger cassettes and chainrings, which leads to more material waste as both have a lot of one-piece construction. Also, the don't get to sell new freehubs to everyone.

I'm pretty sure the XD and XDr hub designs were orginally intended for single chainring applications. In order to get a wide gear range with a single chainring, you either need very large sprockets (with a large chainring) or very small sprockets (with a small chainring). It was probably thought to be easier to use 9 and 10 tooth sprockets, instead of 50 and 60 tooth chainrings.

Originally Posted by yinzerniner

That being said I'm also sure that the 2x FD with a clutch / damper RD works better with the smaller 13t max jumps at the front, so combining the improved FD shifting (which has always been a SRAM weakpoint) with the economic concerns it was a no-brainer from a business standpoint.

Quite possibly. Many new design concepts involve compromises, and often some lesser benefits have to sacrificed to gain greater benefits. There have been many examples of this: Dual pivot brakes have higher leverage and are easier to keep in adjustment than single pivots, but they are also heavier and have smaller rim/pad clearances; indexed shifters/derailleurs are more complicated and more expensive (and also usually heavier) than friction shifters, but can provide faster/more precise shifting; etc. SRAM may believe the benefits of this system outweigh the deficits, and they may be right - but that doesn't mean there are no deficits, or give them free reign to make silly claims.

Originally Posted by yinzerniner

Addressed this in an earlier post, as the "larger sprockets/chainrings are more efficient" argument isn't necessarily true, just that all the test done with existing equipment shows that with that equipment the larger items test better. However that testing was done with non-clutch/damper RDs, current cassettes and typical 11s chains. All three of those variables have been changed with the new AXS group.

Since previous tests were done with then current best available components for 7spd, 8spd, 9spd, 10spd and 11spd equipment, there's little reason to believe that 12spd components will behave any differently.

Tests have shown that clutch derailleurs don't increase drivetrain losses, but so far it has only been hypothesized that they can decrease losses. No definitive proof has yet been given. And if they do improve efficiency, it is not limited to this 12spd system.