  Black hole X-ray binaries are ideal environments to test the accretion
phenomena in the presence of strong gravitational potentials. KERRBB held an
important place in the X-ray spectral continuum method for measuring the black
hole spin modeling the emission from the innermost regions of the accretion
disk. In this work, we present the results of X-ray spectral analysis using
publicly available RXTE data of GRO J1655-40 obtained during the 2005 outburst
with the two relativistic accretion disk models, KERRBB and KYNBB. Our analysis
showed that both models provide identical results with black hole spin
measurements, disk temperature, and disk luminosity when the inner edge of the
accretion disk is set at the innermost stable circular orbit (ISCO) for the
same accretion rates. We couldn't obtain reasonable fits for $\sim$ 89\% of the
observations with a fixed black hole spin value at $\mathrm{a_{*}=0.7}$ using
both models. Allowing the spin parameter to vary improved the fit statistic
significantly with reduced $\rm \chi^{2}$ values being reduced from $\sim$
10-100 to below 2. Both models revealed black hole spin values varying between
$\rm 0.52<a_{*}<0.94$, which can be interpreted as a variable inner edge of the
disk throughout different accretion states.
