  We derive the relative distances to the Virgo, Fornax, and Coma clusters of
galaxies by applying the Dn-sigma and the Fundamental Plane (FP) relations to
the data of the homogeneous samples of early--type galaxies studied by Caon
etal, Lucey etal, and Jorgensen etal. The two distance indicators give
consistent results, the relative distance moduli to Fornax and Coma with
respect to Virgo being Dmu(FV)=0.45+-0.15 and Dmu(CV)=3.55+-0.15) respectively.
The formal error on D(m-M) may be as small as 0.07 mag (~3% in distance),
provided that all the sources of bias are taken into account and a correct
statistical approach is used. Much of the actual uncertainty in the relative
distance of the clusters (12-15%), is due to the existence of systematic
departures in the measurements of the velocity dispersions among the various
datasets, and to the corrections for aperture effects. The above result for the
Fornax cluster is supported by the L-sigma-mu relation and, with lesser
accuracy, by the log(m)-log(re) relations. Our value of Dmu(FV) is in fair
agreement with the one derived using planetary nebulae and SNe-Ia, while is in
open contrast with that coming from surface brightness fluctuations, globular
clusters luminosity function, and infrared Tully-Fisher relation. In our data
Coma appears slightly nearer than indicated by the other distance indicators,
but now a better agreement with the Tully-Fisher relation seems to exist.
Finally we found that there aren't correlations of the residuals of the
Dn-sigma with the effective surface brightness, the total luminosity of the
galaxies, with the ellipticity and the shape parameter a4. Instead a
correlation seems to exists with maximum Vrot, with (V/sigma) and with the
exponent m of the r^1/m fit to major axis light of galaxies.
