In this paper, we aim to uncover previously unknown relationships between readability and phoneme-related features of text. Phonemes are the smallest unit of sound that can distinguish one word from another. Phonemes encode pronunciation, therefore they encode phonetic/auditory details about words that letters do not capture. However, the use of phonemes to aid readability estimation has thus far been limited in literature. This paper aims to bridge this knowledge gap by investigating the relationship between readability and individual phonemes, groupings of phonemes, and phoneme-derived features. The experiments are carried out on the WeeBit corpus. Our findings indicate that phoneme-related properties on their own do not serve as accurate indicators of text complexity.