  Based on the S-matrix approach, we introduce a modified formula for the
$\pi^{\pm}$ electromagnetic form factor which describes very well the
experimental data in the energy region $2m_{\pi} \leq \sqrt{s} \leq 1.1$ GeV.
Using the CVC hypothesis we predict $B(\tpp) = (24.75 \pm 0.38)\% $, in
excellent agreement with recent experiments.
