New chainrings and BB, or new crankset?

Giraffoto

The Tricross has an FSA triple crankset with the usual 50t/39t/30t rings. I never use the inner one, and after a bit of complicated arithmetic I’ve come up with a figure of 36t/46t as being ideal for the way I ride. So what I’m after is a double with 36t and 46t rings.

For about £55, I could get brand new chainrings in that size. Then adjust the front derailleur so it couldn’t go anywhere near the old inner chainring, or leave it there and continue ignoring it.

For another £10 or so, I could get a new BB (it’s a square taper one) to bring the crankset inwards to a double position. But would that be worthwhile? Could the fitting points for the inner chainring then be too close to the frame?

For about £150 I could get a whole new Hollowtech II double crankset, with the size of rings I want (Shimano FC-CX70) and a new BB with external bearings. But would it be worth it? Would I notice any improvement? Are internal BBs any better or worse than external ones, apart from the ease of getting the cranks off?

keef66

Anecdotal evidence suggests the outboard bearings can be shorter lived than the older cassette type Bb's like your square taper job. Get the BB shell faced if you go this route.