2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47394We calculate contributions to the oblique parameters $S$ and $T$ for leptoquarks and bileptons, and find phenomenological constraints on their allowed masses. Leptoquarks suggested by the neutral and charged current anomalies at HERA can give improved agreement with both $S$ and $T$. If bileptons are the only new states, the singly-charged one must be heavier than the directly-established lower limit. We also consider SU(15) grand unification to find when it can be consistent with precision electroweak measurements.4 pages RevTex. 2 figures (gz.tar) included at end. In replacement, only report no. changedHigh Energy Physics - Phenomenologytext