Originally Posted by
Wogsterca
I/m having trouble visualizing that big a cross chaining problem on a double, the gap between the rings should be about double that between cassette cogs, so if the big ring lines up to the 6th cog, the small one lines up to the 4th cog or there abouts on a triple they should pretty much line up to 3-5-7 meaning that cross chaining should only be an issue on maybe one cog on a double, two on a triple, otherwise you lose too many gears if you lose 3 on the bottom and 3 on the top then on a double where there are 18 speeds, your little better off then the 12 speed double on my Raleigh....
The point of a compact double is that there's only a small overlap between the two chainrings. With a 12-27 10 speed cassette and a 50/34 crank, you've got from 33 gear inches to 110 gi. there are only three cogs on the 50 chain ring that overlap with ratios available with the 34. Of those six gears, four (the extreme cross chained ones) are unusable. The lowest usable gear in the 50 tooth ring is about 63 gear inches, which works out to about 15 mph at 80 rpm. The tallest usable gear in the small ring is about 64 gear inches.
While the number of gears actually usable in a 2X10 setup isn't as much bigger then a 2x6 or 2x7, they're better spaced at both ends of the range. I don't actually think compact doubles make sense for non-racers, but that's a different problem.
It's likely the double on your 2X6 Raleigh is something like a 52/42 or 52/40. That's a much smaller difference, and there's a lot more overlap in gears.