But what AMuS report is that TD039 is also being adjusted. The AMuS article is behind a paywall, so I will post the transcription & translation made by this twitter account
AUTO MOTOR UND SPORT [STORY TRANSLATION] - The FIA keeps a close eye on the teams. Because there was too much trickery with both the base plate and the wings, new rules come into force in Singapore.
On August 22nd, the teams received mail from F1 Technical Director Tim Goss. The former McLaren engineer sent out two technical directives that have existed for a long time, but have to be modified again and again because teams keep finding new ways to outsmart the regulations.
The TD018 deals with the flexibility of fairing parts on three sides. It comes into force in Singapore. TD039 defines the rules for the floor panel fastenings and the aerodynamically generated rocking of the cars. The adjusted seven-page interpretation of TD039 generally applied as of the date of mailing. The stricter regulations contained therein for the front part of the guard rail will only come into force from the race in Singapore.
In an effort to minimize car bottoming for safety reasons and to protect drivers, a measurement was introduced in Spa last year that measures the vertical movements of the car and the impact as it hits the road. Anyone who exceeds a certain level, which is calculated using a complicated formula, has to make improvements. Roughly speaking, the limit is 8 g.
The guardrail under the car proved to be an inadequate tool to prevent too much contact with the ground. Although it is only allowed to wear a maximum of one millimeter in certain places during the race, the teams quickly found tricks to protect the plank even when it hits the ground.
The FIA is trying to put a stop to floor tricks. For example, with an insulating material between the chassis and the base plate that softens the shocks. Or fastening screws that protrude slightly and disappear into the plank when they come into contact with the road, thus also having a dampening effect. The TD039 put an end to that. A year has now passed and the teams have already discovered new loopholes. The newly added paragraph 1.3 is now intended to fill this in as well.
The text reads in official English: "We have noticed design details in the designated holes in the floor skid area that are designed to maximize the allowable stiffness in these areas. While these designs may meet the deflection requirements, we would like the teams to do so Remember that designs must still conform to the dimensional constraints of the corresponding trim parts, which state that there must be a continuous surface on the reference plane. Designs must not use breaks in this surface to allow for differences in vertical stiffness at these break points"
The FIA specifies in four points what it considers to be illegal in the future: gaps, cuts or butt joints in the relevant part of the reference plane, systematic damage, cracks or breaks on the surface of the reference plane near the holes intended for the skids, highly flexible materials on the plank or folded surfaces and connections.
Who thwarted the rules?
Most teams appear relaxed and claim that they don't need to adapt their cars. In fact, at Monza there was a rush to the FIA measuring platform to find out whether you were over the limit or not.
Haas reported that the rear wing needs to be slightly improved (in response to TD018). At Williams the focus is on the floor.
Wolff mentioned that Aston Martin had already taken a step back & it will now be interesting to see who still needs to improve. And how that affects the lap times in Singapore.
There were rumors that Mercedes would be affected by the rear wing and Red Bull by the floor. Which of course is not confirmed.
Christian Horner went on the offensive in Monza: "There's nothing that concerns us. We discovered a few rubber noses on other cars and are now waiting for them to disappear."
An engineer estimates the effect of the wing TD to be greater than the restrictions on the floor: "If you have to make corrections to the floor and as a result leave a little more ground clearance, in the worst case scenario you will lose downforce. If the front wing is twisted around the attachment point on the nose. Then the entire aerodynamics were designed accordingly. If you have to take a step back, you not only risk a loss of downforce but also balance problems."