FIA forces Mercedes to strip diffuser spikes after Ferrari-led rival complaints

Mercedes has been compelled to alter a novel diffuser design introduced at the Canadian Grand Prix after the FIA issued a technical directive in response to complaints from Ferrari and several other teams. The changes, which remove the distinctive spike-like profiles from the upper section of the W17’s diffuser, were already visible on the car during media day in Austria.

The upgrade package Mercedes brought to Montreal was the team’s first significant one of the season, covering the front wing and floor as well as the rear of the car. It was the diffuser additions that drew the most scrutiny — serrated profiles running across more than half the diffuser’s upper width, designed to extend its effective area and enhance downforce generation.

After Ferrari spotted the solution, the Scuderia asked the FIA for clarification and sought permission to develop a similar design, but was not given the green light. Motorsport.com has learned that the FIA’s primary concern was not that the Mercedes design was immediately illegal, but that it could open the door to more creative interpretations the governing body would not be comfortable with. That prompted the technical directive issued following the Barcelona Grand Prix.

The directive comes into force from the Austrian Grand Prix weekend. From 2026, such documents will be referred to as FIA docs rather than technical directives — a terminology change for consistency purposes only, as the scope of what they can cover remains the same.

Mercedes has acknowledged that the new guidelines required “minor tweaks” to the diffuser. The extensions themselves remain on the W17 in a reduced form, but the spike-like profiles have been removed. Racing Bulls has also been asked to modify its own diffuser extensions under the same directive.

The situation has not entirely closed off this area of development. Teams in the paddock have confirmed that while the specific implementation Mercedes used in Montreal is now prohibited, virtually all constructors are still exploring ways to effectively extend the diffuser within the updated guidelines. The current rules still leave meaningful room to work in this space — just not in the more extreme form Mercedes pioneered.