The "effective" relaxation time tau of isolated star polymers with excluded volume interactions in the Rouse model limit (i.e., disregarding hydrodynamic interactions present in real solvents) is studied varying both the number of arms f and the number of monomers per arm l. Here tau is defined from the response of the gyration radius of the star polymer to a Kramers potential that describes the effect of shear how in lowest order in the shear rate. Monte Carlo simulations are performed with two different techniques (simple sampling with enrichment or dynamic Monte Carlo, respectively) for two different models (simple self-avoiding walks with an extended core or the bond fluctuation model, respectively). It is proposed that the ratio tau(f,l)/tau(1,l) should be a universal function of f for large l, and the Monte Carlo data are used to test this hypothesis.