An EZNEC simulation of a 160 meter dipole 70' above average ground, for bare wire, shows these 2:1 VSWR bandwidths:
#10, 67 kHz
#14, 63 kHz
And about a 3.5 kHz shift in resonant frequency due to the wire diameter. (Higher frequency for
By the time you string a 160m dipole across a typical property, the variation due to other
factors will be more important.
At VHF/UHF the diameter in wavelengths
is much larger, especially when using rods or tubing
rather than wire. That's why you see more variation due to conductor diameter.