Simple 29-year-old rule Hamilton, Leclerc broke in accidental DQ ...

Lewis Hamilton and Charles Leclerc were two standout performers at the United States Grand Prix, with Leclerc taking an unlikely pole position on Friday and Hamilton coming close to overhauling Max Verstappen for victory on Sunday.

By Sunday night they were notable for a completely different reason: both were disqualified from the race.

Disqualifications are rare, reserved largely for technical breaches and the most serious sporting breaches relating to the fairness of competition.

Their offence was to run their cars too low based on a rule introduced almost 30 years ago.

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The effect of their disqualifications extends to more than just pride.

Hamilton has lost ground to Sergio Pérez for second in the drivers championship. He would have got it down to 19 points, but with four rounds to go the margin has blown out to an unlikely 39 points.

Leclerc’s DSQ, combined with Lando Norris rising to second, means the Monegasque has dropped eight points behind the Briton to seventh in the standings.

Just 22 points separate Mercedes from Ferrari in the battle for second in the constructors championship, but it was a marginally more comfortable 31 points before the disqualifications.

On the bright side — for some, anyway — both Williams drivers moved into the points, including Logan Sargeant for the first time in his F1 career. It takes the team to 10 points ahead of Alfa Romeo for seventh in the teams standings.

In short, the pair of disqualifications have had far-reaching consequences. So why and how did they happen?

WHY WERE HAMILTON AND LECLERC DISQUALIFIED?

It might surprise new and even some longstanding fans to know that in the super-high-tech world of Formula 1 racing, ride height is regulated by a piece of wood screwed into the bottom of the car.

The plank, as it’s officially known in the rule book, is exactly 1 centimetre thick and placed in a specific area in the middle of the car’s floor.

Attached to the plank are the skid blocks, which are made from a titanium alloy and protrude slightly from the wood. These blocks are what cause the spectacular sparks from beneath the car whenever it gets too low to the ground.

The skid blocks are in place to protect the floor and plank when the car bottoms out. The titanium takes the hit instead of the wood so that at the end of the race the plank will measure no less than 0.9 centimetres.

Losing 1 millimetre of plank thickness is permissible through general wear and tear. Lose 1.1 millimetres and you’re out.

The plank exists as a cleverly simple solution to police ride height. Measuring the height of the car before and after the race wouldn’t be enough, because teams would come up with ways for the car to hunker down at high speed. By introducing a consumable part, the regulation effectively polices itself.

Teams prefer to run their cars as low to the ground as possible because it improves aerodynamic performance.

If a car can ‘seal’ the floor area of the car — that is, have air go directly from front to back without spilling out of the sides — it can produce massive downforce. The closer they can get to the ground, the better sealed the floor is.

But sometimes teams must be protected from themselves. The plank was introduced as part of a raft of safety-oriented changes in 1994 following Ayrton Senna’s death. Some at the time speculated the Brazilian’s car had catastrophically bottomed out in that fateful San Marino Grand Prix, sending him into the barriers.

Though cars have changed a great deal since then, the basic principles of performance and safety remain.

WHY DID THEY BREAK THE RULE?

Ferrari and Mercedes would not have intentionally broken this regulation. The risk of disqualification is too great.

Instead both teams would have arrived here by accident.

It’s not surprising this happened at the Circuit of the Americas and on a sprint weekend.

COTA is a very bumpy circuit, perhaps the worst on the calendar.

Several theories for its bumpiness have been floated. One is that the type of clay the circuit is built on shifts with rainfall, disrupting the asphalt.

Others have theorised the track simply wasn’t laid properly, with Silverstone’s bad resurfacing job and subsequent need to resurface a second time in 2018 and 2019 respectively proffered as evidence.

Whatever the reason, the bumps are not just a driving challenge but a set-up issue too.

With just one hour of practice this weekend on account of the sprint format, teams had an unusually short period to find the right ride height. They didn’t have enough time to conduct the sort of heavy-fuel race simulations they would usually reserve for FP2 on a Friday afternoon.

In the case of Mercedes and Ferrari, the dual elements of the bumps, which ride up and whack the bottom of the cars, and the compressed schedule conspired to put them over the limit.

Mercedes might also have been caught out by the new floor brought to the car in Austin. The boost in performance is unlikely to have had a noticeable effect on ride height, but the complication of assessing its working range and setting it up may have contributed to failing to account for the other factors.

HOW DID THEY GET FOUND OUT?

FIA stringently polices the technical rules throughout the weekend and in several different ways.

Long-time FIA technical delegate Jo Bauer oversees scrutineering and “carry out, or have carried out by scrutineers, at his discretion, any checks to verify the compliance of the cars entered in the competition, at any time until the end of the competition, without prior request from the stewards or clerk of the course”, according to the regulations.

Scrutineering happens regularly, but it’s perhaps at its most high profile during qualifying, when drivers are randomly called to the weighbridge in pit lane for a series of checks that can take up to a few minutes.

Scrutineering procedures are broad and range from weighing the car to ordering a team completely dismantle a car to prove it’s in compliance with the rules.

Some parameters are checked on every car regularly. But because the technical regulation run to 183 pages, some more detailed checks are carried out randomly on a smaller number of cars for practicality.

Measuring the thickness of the floor is one of those limited random checks.

On Sunday night only Hamilton, Leclerc, Verstappen and Norris were checked. Verstappen and Norris’s cars were in compliance, Hamilton and Leclerc’s cars were not.

Bauer found excess wear on the skid blocks and reported it to the stewards. Bauer is the policeman in this situation, the stewards are the court.

Mercedes and Ferrari attempted to plead their case, but there were no overwhelming mitigating circumstances, and the stewards meted out punishment.

ISN’T DISQUALIFICATION HARSH?

Breaking the technical regulations comes with an automatic disqualification. On some rare occasions teams may be able to argue for leniency based on some external, unavoidable factor, but in almost all cases it’s a black-and-white, open-and-shut case.

Given how much performance can be gained from even minor breaches of the technical rules, stringent policing is crucial to ensuring fairness in competition.

Think of it like the anti-doping code. World anti-doping bodies take a zero-tolerance approach to doping both to preserve the integrity of competition as well as to deter competitors from risking it. The punishment becomes a form of policing.

Breaking the technical rules can be thought of as a form of mechanical doping. And just like in the world of actual doping, you don’t have to prove the action had any beneficial effect or even that the actor had any intent to dope. It just has to have happened.

Mercedes and Ferrari wouldn’t have done it deliberately and probably derived no performance benefit — the constant bottoming-out of the car may even have made them slower — but that’s not relevant. Just operating outside the rules is enough.

ARE DISQUALIFICATIONS COMMON?

The success of the zero-tolerance approach is that disqualifications are extremely rare. Only eight drivers have been stripped of position in the last decade, six of whom had committed a technical breach.

The first was Daniel Ricciardo, who was thrown out of the 2014 Australian Grand Prix for breaching fuel-flow limits in the very first race of that rule’s operation.

In 2015 Felipe Massa was disqualified from the Brazilian Grand Prix due to tyre temperature irregularities on the grid.

Romain Grosjean was eliminated from the 2018 Italian Grand Prix for using an illegal floor.

The 2018 United States Grand Prix saw Esteban Ocon and Kevin Magnussen both disqualified for using too much fuel, the former exceeding fuel-flow limits on the first lap and the latter using too much fuel over the race.

Sebastian Vettel was the most recently disqualified driver before this weekend, having been stripped of what would have been his last F1 podium finish at the 2021 Hungarian Grand Prix for not having one litre of fuel left in the car for scrutineering at the end of the race.

The only exception was Ricciardo and Nico Hülkenberg’s disqualifications from the 2019 Japanese Grand Prix for using a brake bias system that was declared an illegal driving aid after protest from a rival team.

Driving aids are covered under the sporting regulations — the clause stipulating a driver must drive the car alone and unaided — but Renault arrived at the system trying to operate in a grey area of the technical rules.

Hamilton and Leclerc — and Mercedes and Ferrari — are new and unwanted additions to the list.