Sorry, been away most of the week. There's been a few questions off the back of my post about SRAM doubles. To try and explain better what I mean let me try and do it from my requirements. I emphasize that their mine YMMV.
First off I'm talking about touring not sport or around town. I need a range of gears from just below 2 metres up to 8 metres (I know some of you prefer gear inches rather than roll out but I don't ride ordinaries
). I also need them at about .5 metre intervals as far as possible. Bigger than that leaves too big a gap in effort and smaller is only necessary for the fine tuning needed when the priority is to go as fast as possible. This too me is where Rohloff have got it exactly right.
So if we say 1.5m to 8m that means I need 14 gears ( I can't ride 1.5 'cos it's too small for me, 1.8 or 1.7m would do fine ). Allowing for chain crossing and duplicates a 3x7 transmission gives me that already. 3x8 and 3x9 just gives me more of nothing, 3x10 gets to be a nuisance because a 1 sprocket change often doesn't produce the difference I want.
For me a 44-32-22 chainset with an 11-34 9 speed cassette is crazy. There's far too many low gears that are far too close to each other and at the other end there's an enormous gap between an 11 and a 13 sprocket.
My ideal touring set up could be a 7 speed triple. 48-38-28 and 13-34 for loaded touring and a 13-30 unladen. A 7 speed 135mm hub is a wonderful thing too with very little dish. Problem is that quality 7 speed stuff is hard to find now. Even if you went with friction levers hubs are hard to find.
If you want to render the same with contemporary components a triple doesn't make sense. There's far too many gears for a start. If you want off the shelf ( with drops ) then neither C or S offer the range you want. If you want to mix road and MTB stuff then front mechs are a problem area ( and rears too as quality 9 speed stuff disappears).
So a super compact set up reccomends itself. With 10 speeds upwards and more flexible chains it can easily give the range and gaps I specified above. A mix and match of SRAM road and MTB will give it to you off the shelf. If you don' t want an MTB chainset then this is possible. Several niche manufaturers make 46-30 chainsets. Sugino make one thar goes smaller. A TA or Middleburn set up where with different spiders allows you to make what you like. Putting custom rings on the inner and middle of standard cranks does too.
I accept that at the extremes a triple might have a greater range - if someone's got a 54-38-22 triple to work it would be hard to match. But for more mundane cases it's true. I need 14 gears not 30 so a triple offers nothing here over a double. The downside of 50-34 compact in putting the chainring change right in the middleof the most used gears doesn't apply - you've split into a high set and a lower set of gears.
So, yes, using SRAM for touring makes perfect sense.