The simple F1 plank rule that is more complicated under the surface

A Formula 1 car is made up of thousands of intricate components, each one, if you find beauty in engineering, a work of art. Exotic metals are machined into intricate shapes or grown into yet more intricate shapes by 3D printing. Advanced composite materials are analysed to the nth degree to ensure the layup of the various fibres and the resin encapsulating them is the exact solution to a complex three-dimensional problem.

And yet, one of the simplest parts of the car has this year attracted more attention than any of the sophisticated components. I’m talking about the plank or, as it was known in the early days, the skid block. It has attracted particular attention after the disqualifications of Lewis Hamilton in China and Nico Hulkenberg in Bahrain before the more recent, and perhaps more significant, disqualification of both McLaren cars in Las Vegas.

The plank was one of a raft of measures introduced mid-season in 1994 to slow cars down after the fatal accident of Ayrton Senna. In those days, the regulations governing bodywork ran to 674 words, rather different to the 19,000 words of the 2025 bodywork regulations, and much of that complexity has come about as teams better understood the aerodynamics of their cars and how best to set them up for maximum performance.

In 1994 we had true flat-bottom cars. The step plane, which is a region of the outer edges of the floor that had to sit 50mm above the central, 300mm wide, reference plane, was not introduced until the following year. Then FIA president Max Mosley felt that if the cars were forced to run at a higher ride height, they should be slower, more stable and hence safer.

Prior to the complications of the step plane, the easy way to do this was to mandate a 10mm thick skid block beneath the car. This had to be 300mm wide and run from a position in line with the rear edge of the front wheels to the centre line of the rear wheels. This was announced in May and was to be fitted for the German GP on 31 July. The regulations stated that the 10mm plank must not wear below 9mm during the race.

With such a rapid design cycle required, teams chose a material they knew well from which to make the skid blocks. This was Jabroc, which had already been used for rubbing strips on skirts and front wing endplates. It is made from beech wood that’s impregnated with a resin and then compressed at high temperature to produce a hard composite of wood and resin. It increases the specific gravity of the wood from around 0.7 to about 1.3.

Symonds was involved in the very first plank wear disqualification, when Schumacher was struck from the results of the 1994 Belgian GP

Photo by: Motorsport Images

I was involved in the very first disqualification for an infringement of plank wear rules, at the 1994 Belgian GP with Michael Schumacher. In a similar manner to this year’s Las Vegas incidents, we had suffered from having no real dry running until the race and, together with very little experience of the plank, we ended the race in first place but with a plank that was below 9mm in a few places. We argued that this was the result of an off earlier in the race and also that correct measuring procedures had not been carried out. Our arguments, even in the court of appeal, were futile and our disqualification stood.

As understanding progressed, Jabroc fell out of favour. It’s still used in F2 as it’s a relatively cheap material, but in F1 it has been replaced by a glass composite known as Permaglass. This has a similar density but is more stable than the wood, as well as being more abrasion resistant.

It’s this extraordinary performance gain from ultra-low rear ride heights that’s caused McLaren and Ferrari plank wear problems

Aerodynamically, prior to the 2022 regulation reset, most teams found that running the car with a very low front ride height gave gains. This brought the front wing closer to the ground, improving the load generation of the mainplane and allowing the flap to be backed off to get the correct aerodynamic balance and better airflow to the rear. Ultimately most cars developed to very high rear ride heights, which, as the car pivoted about the front wheel, brought the wing closer to the ground and lifted the plank, which was behind the front wheel centre line, thereby allowing an even lower front ride height. The problem then was one of wearing the front of the plank.

The 2022 regulations reset things in that the ground effect rewarded running the rear of the car very low, and the gains to be had from this were so great that teams left little safety margin on rear ride heights. It’s this extraordinary performance gain from ultra-low rear ride heights that’s caused McLaren and Ferrari plank wear problems this year.

This article is one of many in the monthly Autosport magazine. For more premium content, take a look at the January 2026 issue and subscribe today.

Both McLarens were disqualified from the 2025 Las Vegas GP for excessive plank wear

Photo by: Clive Mason / Getty Images