Rhythmic patterns related to Brazilian Portuguese adjacent stresses and secondary stress were investigated under a dynamical systems perspective. Paired utterances contrasting alleged stress clash vs non clash reveal a duration pattern difference in the opposite direction of the Rhythm Rule: the closer a syllable-sized unit is to phrase stress, the longer its duration. Polysyllabic words may exhibit initial lengthening as a possible indication of an initial secondary stress. The two phenomena are simulated by using the same parameters with the coupled-oscillators model of speech rhythm production.