This study presents an experimental methodology for characterising the mechanical behaviour of sandy subgrade soils under unsaturated conditions, with relevance to pavement design and performance assessment. Repeated Load Triaxial (RLT) tests were conducted under controlled suction states on three sandy soils with varying fines content, aiming to evaluate resilient modulus (MR) as a function of moisture and matric suction. Suction equilibrium was achieved externally through water content control, and the corresponding suction levels were inferred using soil water retention curves (SWRC) established for each material. This approach enabled testing across a realistic range of field moisture conditions while maintaining repeatability and control over suction states. The results show that MR increases with decreasing moisture and increasing suction, highlighting the importance of accounting for unsaturated conditions in subgrade characterisation. The methodology demonstrates a viable laboratory procedure for capturing suction-dependent mechanical behaviour and offers insights into how such behaviour may influence pavement foundation design.