  The peaks of 30 optical afterglows and 14 X-ray light-curves display a good
anticorrelation of the peak flux with the peak epoch: F_p ~ t_p^{-2.0} in the
optical, F_p ~ t_p^{-1.6} in the X-ray, the distributions of the peak epochs
being consistent with each other. We investigate the ability of two
forward-shock models for afterglow light-curve peaks -- an observer location
outside the initial jet aperture and the onset of the forward-shock
deceleration -- to account for those peak correlations. For both models, the
slope of the F_p - t_p relation depends only on the slope of the afterglow
spectrum. We find that only a conical jet seen off-aperture and interacting
with a wind-like medium can account for both the X-ray peak relation, given the
average X-ray spectral slope beta_x = 1.0, and for the larger slope of the
optical peak relation. However, any conclusion about the origin of the peak
flux - peak epoch correlation is, at best, tentative, because the current
sample of X-ray peaks is too small to allow a reliable measurement of the F_p -
t_p relation slope and because more than one mechanism and/or one afterglow
parameter may be driving that correlation.
