  We present a new dispersive framework for the extraction of the strong
coupling constant $\alpha_s$ from $\tau$-lepton decays. A new feature of our
procedure is the use of the quark-hadron duality on the limited region $s_{\rm
d}<s<m_{\tau}^{2}$. The duality point $s_{\rm d}$ and the $\bar{\rm MS}$ strong
coupling constant $\alpha_{s}(m_{\tau}^{2})$ are self-consistently extracted
from the $\tau$ data for the non-strange vector spectral function. We use 2005
ALEPH and 1998 OPAL experimental data on the vector spectral function. We
compare the new framework with the contour improved perturbation theory up to
order $\alpha_s^{5}$. The new procedure yields systematically lower values for
$\alpha_s$. From the 2005 ALEPH data, we obtain
$\alpha_{s}(m_{\tau}^{2})=0.308\pm 0.014_{\rm exp}\pm 0.005_{\rm th}$ which
corresponds to $\alpha_{s}(M_{\rm_{z}}^{2})=0.1170\pm 0.0018_{\rm exp}\pm
0.0007_{\rm th}\pm 0.0005_{\rm ev}$. The extracted value for the duality point
$s_{\rm d}$ is found surprisingly stable against perturbation theory
corrections $s_{\rm d}= 1.71\pm 0.05_{\rm exp}\pm 0.00_{\rm th}\,\, {\rm
GeV^{2}}$. From the 1998 OPAL data, we obtain
$\alpha_{s}(m_{\tau}^{2})=0.290\pm 0.023_{\rm exp}$ and $s_{\rm d}=1.68\pm
0.10_{\rm exp}\,\, {\rm GeV^{2}}$.
