Ball-and-socket helmet construction changes the math on rotational impacts, and the Helios Spherical builds that approach into a road and gravel lid without the flagship-tier price. Giro's Spherical Technology uses a ball-and-socket design powered by Mips that allows the helmet's outer liner to rotate around the inner liner during a crash, and also enables Progressive Layering of the inner and outer liners. In practice, the sliding layer is integrated right into the foam structure itself rather than added as a separate yellow plastic sheet pressed against your scalp — a design choice that anyone who's worn an early-generation Mips helmet will immediately appreciate.

The sliding Mips layer is integrated into the helmet itself as essentially an EPS shell within an EPS shell, with the two shells moving independently of each other via 10-15mm of travel thanks to a low-friction layer sandwiched between them and secured with elastomer anchors. The exterior polycarbonate shell is in-molded, permanently fused with the EPS foam liner for increased durability. The Progressive Layering part matters too — two different density EPS foam liners address high- and low-speed impacts for more comprehensive energy management rather than tuning for a single crash scenario and hoping the rest works out.

Cooling is where the Helios actually pulls ahead of some more expensive helmets in the Giro range. Giro says the Helios is two per cent less efficient on cooling than the Aether because the Aether has bigger but fewer channels — 11 compared to the Helios's 15 — but it's a difference most riders won't notice. The massive vents combine with internal channeling that forces air to flow over the scalp, while the Roc Loc 5 Air fit system adds a new dimension by enhancing cooling as well as fit comfort and stability. The patented design suspends the helmet just slightly off the top of the skull, allowing cool airflow to pass directly over your head.... Read More