  Estimating the bar pattern speed (\Om{}) is one of the main challenges faced
in understanding the role of stellar bars in galaxy dynamical evolution. This
work aims to characterise different uncertainty sources affecting the Tremaine
Weinberg (TW)-method to study the correlation between bar and galaxies physical
parameters. We use a sample of 15 MaNGA SDSS-IV galaxies and 3 CALIFA galaxies
from \cite{Aguerri2015}. We studied the errors related with (i) galaxy centre
determination, (ii) disc position angle (PA) emphasising the difficulties
triggered by outer non-axisymmetric structures besides the bar, (iii) the slits
length and (iv) the spatial resolution. In average, the PA uncertainties range
$\sim 15 \%$, the slit length $\sim 9 \%$ and the centring error $\sim 5 \%$.
Reducing the spatial resolution increases the sensitivity to the PA error.
Through Monte Carlo simulations, we estimate the probability distribution of
the \R{} bar speed parameter. The present sample is composed of 7 slow, 4 fast
and 7 ultrafast bars, with no trend with morphological types. Although
uncertainties and low sample numbers may mask potential correlations between
physical properties, we present a discussion of them: We observe an
anti-correlation of \Om{} with the bar length and the stellar mass, suggesting
that massive galaxies tend to host longer and slower bars. We also observe a
correlation of the molecular gas fraction with \R{}, and a weak
anti-correlation with \Om{}, suggesting that bars rotate slower in gaseous
discs. Confirmation of such trends awaits future studies.
