WHAT A precise frame sizing method that’s based on effective stack (X) and reach (Y) to the aerobar pads.
WHY Allows the rider to determine their appropriate bike size and more closely replicate their fit from bike to bike, rather than relying on traditional top tube measurements. A fine-tuned fit is especially important for triathlon bikes, where the rider must hold a fixed position for an extended period of time.
HOW Measures the height of the aerobar pad above the bottom bracket (effective stack) and how far the pad sits in front of the bottom bracket (effective reach).