Most FD have sufficient travel to accommodate triple cranks, but there are differences.
FD cages are curved to best fit with outer chainrings of certain size ranges, ie, 52-53 road, 48-50 compact drive, 46-48 mtb. Also the length and drop of the back of the cage determines the minimum size granny they'll fit. Most atb FD,s will work with a 24t granny, most road FD are limited to inners of 38t or more, though road triples can go smaller.
So don't sweat double or triple as much as the chainring sizes it'll work with.
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