I am wondering about a problem very similar to the original poster. The chain on my new road bike, a Fuji Roubaix Pro, rubs against the front derailleur cage when the chain is on the larger of the two front chain rings and the largest of the rear cogs, and also when the chain is on the small front ring and the smallest rear cog.
I thought this seemed odd and took it back to the bike shop. They told me this is normal as these are gearings that aren't usually used and shouldn't be used. I thought it this was odd, but the known Park Tool website states something similar:
The front derailleur should shift the chain between chainrings without throwing the chain off the extreme outer and inner rings. It is possible that the front derailleur will rub the chain slightly even on properly adjusted bikes. This is likely on some bikes when riding in the largest sprocket in front and the smallest cog in back. As the bike is pedaled with force the frame flexes and moves the chainrings side to side, which cause an intermittent rubbing noise. Loosening the H-limit would move the front cage out more, and may stop the rubbing, but it may also cause the chain to shift over the largest ring and come off. If all aspects of front derailleur adjustments are correct on this bike, the rider is simply exceeding the engineering and design capabilities of the machine.
Link for above (last paragraph):
http://www.parktool.com/repair/readhowto.asp?id=75
Is this actually normal? Why would a bike not be able to use some of it's gears?
Bike info:
2 front rings, 10 rear
Front Derailleur: Shimano 105, FD-5500, clamp-on, 28.6mm
Detailed info:
http://www.fujibikes.com/2002/usa/ht...roubaixpro.htm