  We have investigated the motion of vortex domain walls passing across non
symmetric triangular notches in single Permalloy nanowires. We have measured
hysteresis cycles using the focused magneto-optical Kerr effect before and
beyond the notch, which allowed to probe beyond the notch the occurrence
probability of clockwise (CW) and counter-clockwise (CCW) walls in tail-to-tail
(TT) and head-to-head (HH) configurations. We present experimental evidence of
chirality flipping provided by the vortex -- notch interaction. With a low exit
angle the probability of chirality flipping increases and here with the lowest
angle of 15$^o$ the probability of propagation of the energetically favored
domain wall configuration (CCW for TT or CW for HH walls) is $\approx 75\%$.
Micromagnetic simulations reveal details of the chirality reversal dynamics.
