2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/125009Using the elegant method employed recently by Erickcek, Smith and Kamionkowski, on the premise that the space-time of Solar System is described by a metric with constant-curvature background added by a static perturbation, we show that many $f(R)$ gravities are ruled out by Solar System tests.7 pages, no figure. some discussions and references added; typos corrected minor revisionAstrophysicstext