  We describe very accurate imaging of radio spectral index for the inner jets
in three FR I radio galaxies. Where the jets first brighten, there is a
remarkably small dispersion around a spectral index of 0.62. This is also the
region where bright X-ray emission is detected. Further from the nucleus, the
spectral index flattens slightly to 0.50 - 0.55 and X-ray emission, although
still detectable, is fainter relative to the radio. The brightest X-ray
emission from the jets is therefore not associated with the flattest radio
spectra, but rather with some particle-acceleration process whose
characteristic energy index is 2.24. The change in spectral index occurs
roughly where our relativistic jet models require rapid deceleration.
Flatter-spectrum edges can be seen where the jets are isolated from significant
surrounding diffuse emission and we suggest that these are associated with
shear.
