Mercedes arrived at the Canadian Grand Prix with its most significant upgrade package of the 2025 season — and it didn’t take long for the pitlane to sit up and take notice. The Mercedes F1 diffuser, fitted to the W17 driven by championship leader Kimi Antonelli and George Russell, featured a revised front wing and floor alongside several eyebrow-raising solutions at the rear of the car. It’s the rear-end trickery, however, that’s sparked a proper row.
Mercedes F1 Diffuser Design Draws Immediate Rival Scrutiny
Since winter testing, every team on the grid has been hunting for clever ways to extend diffuser performance — particularly because the current generation of machinery leans less heavily on ground effect than its predecessors. Mercedes’ Montreal-spec solution was bold: serrated, spike-like profiles running along more than half the width of the upper diffuser section on the W17. The intent was clear — push the diffuser’s effectiveness further without technically breaching the regulations.
Ferrari spotted it almost immediately. The Scuderia approached the FIA for clarification, asking specifically whether they could develop something along the same lines. The answer, according to Motorsport.com, was no. The governing body reportedly wanted to stamp its authority quickly, concerned that the Mercedes approach could crack open a door to increasingly creative — and increasingly extreme — diffuser solutions it wouldn’t be comfortable policing down the line.
FIA Technical Directive Forces Changes Ahead of the Austrian Grand Prix
Consequently, a technical directive dropped after the Barcelona Grand Prix, coming into force from the Austrian Grand Prix weekend onwards. From 2026, such documents carry the label ‘FIA doc’ rather than technical directive — a consistency measure covering everything from sporting to technical matters — but the impact remains the same.
Mercedes confirmed it needed to make ‘minor tweaks’ to comply, and those changes were already visible in media day photographs in Austria. The spike profiles are gone. The diffuser extensions themselves remain, just in a less aggressive form. Importantly, Racing Bulls also received instructions to modify their own diffuser extensions.
Nevertheless, the situation isn’t entirely closed off. Multiple teams in the paddock confirm there’s still room to explore this area — provided nobody goes as far as Mercedes did in Montreal. Ferrari’s 2026 challenger, the SF-26, already shows diffuser extensions in available imagery. Customer team Haas runs a similar concept, using multiple elements. Both, like Mercedes’ revised Austria-spec setup, sit within the limits of what the FIA now permits.
The message from the governing body is straightforward: innovate by all means, but don’t push it. For Mercedes and their rivals, the diffuser development race continues — just with tighter boundaries drawn around it. For more from Austria this weekend, check out our piece on Verstappen backing Red Bull’s new package to close the gap at the front.