It is said that driving a race car in the wet brings out the most skilled drivers and distinguishes them from the rest of the pack. The utmost precision in technique and car control, alongside enormous commitment is required to extract the most from the vehicle. Ayrton Senna was famous (amongst other things) for his impeccable wet-weather racing on almost every occasion. The rain minimises the performance differences in machinery too, as those who have superior feel for their car can outperform those with statistically faster hardware.
The fact is that racing in the wet is incredibly unnatural to many racing drivers. When driving in the dry, the ‘racing line’ is the fastest route to navigate a lap of the race circuit, maximising the radius of any corner taken to carry more momentum. When cars drive over the racing line, a layer of rubber is built up on the track, as each car’s tyres slip along the surface and deposit small rubber particles. This rubber build-up can then sit nicely in the naturally abrasive, bumpy asphalt surface, causing the grip levels to increase further as the sticky surface gets laid down. This is where the phrase ‘laying down rubber’ or ‘rubbering in the track’ comes from. However, when the rain arrives, this rubbered surface becomes incredibly slippery, as the tyres now have a thin barrier between their surface and the track below. The typical racing line that has been drilled into the minds of developing drivers progressing through their careers must be ignored: the car becomes extremely sensitive under acceleration due to heavily reduced traction, the limited lateral forces available from the tyres causing the car to resist turning. Braking distances are lengthened, and extra care must be taken over areas of standing water that can suddenly fling the car into a spin or unanticipated aquaplaning without any notice. Driving away from the rubbered racing line allows the tyres to make a larger contact patch with the abrasive asphalt surface as opposed to the slippery rubber build-up, increasing grip. Of course, this is also combined with a wet-weather, treaded tyre that can displace the water as the car runs over the track.
This is shown in the above diagram, taken from grassrootmotorsport.com : Learning to Race in the Rain.
The driver must carefully pick a new route to navigate each corner, crossing the rubbered line as few times as possible. This includes braking on the inside of the corners, braking deep and crossing over the typical racing line, rotating the car as quickly as possible before progressively building the power early.
This must all be done whilst the driver is trying to race against many other competitors out on circuit, alongside managing the performance of the car itself. It’s incredibly easy to make mistakes, and really gives insight into just how talented the exceptional wet weather drivers are. Due to the nature of weather, the track conditions can constantly change, known as mixed conditions. If the track starts dry but rain arrives, or vice versa, the given grip level down any straight or corner can vary widely, even lap-to-lap. Great drivers can find the limits of the car through any corner, rapidly and in spite of changing conditions.
However, the story may be changing for wet weather driving in the top echelon of motorsport. Modern Formula 1 circuits are held to the highest available FIA safety standards and are resurfaced roughly once a decade. Modern resurfacing techniques, alongside updated asphalt compounds, result in a very densely packed surface, where the abrasive gaps and micro bumps are extremely minimal compared to older tracks. This has a big implication for wet weather driving, as now, whilst the rubber is still laid down on the track surface in dry running, the introduction of water is more likely to wash the embedded rubber surface particles away, as there are fewer cracks and track abnormalities for the rubber to fill.
This allows additional options to take advantage of the traditional racing line in wet weather conditions, as the surface is far less slippery than it might have been had the asphalt retained more of the laid-down rubber. This phenomenon was clearly seen in the 2021 Belgian GP qualifying sessions.
George Russell managed to place his Williams, a car lacking in performance compared to the front runners, on the front row of the grid throughout a mixed condition session. Many drivers were avoiding the rubbered racing line surface in order to maximise their grip in the wet conditions. However, George Russell had generated a massive 1.7 second advantage over Lewis Hamilton’s previous best lap, with the majority of this time coming in the first sector alone. While braking away from the rubbered line, Russell had instead opted for the more traditional racing line in the first hairpin, gaining him massive amounts of time down the incredibly long straight towards the next corners.
One reason behind this could be a naturally drying track allowing more grip at the regular apex of the corner. However, Lewis Hamilton then goes quickest in the middle sector, by taking the more traditional racing line through the corners of No-name, Pouhon and the Les Fanges chicane, while Russell avoided it. Evidence suggested that when the track was still wet and raining, use of the dry racing line, by maximising the turning radius of the cars and carrying more momentum through the corners, was yielding more time gains than avoiding the supposedly more slippery rubber surface. The Belgian GP of 2021 went on to be a race mired in controversy, as the race was not carried out over full distance, only managing 2 laps behind the safety car before a red flag was thrown, with half points awarded to the top 10 based on lap 1 positions.
This does not mean that driving away from the traditional racing line when the rain comes is now extinct in Formula 1, as any rubber that does happen to build and embed itself into the track surface will provide incredibly poor traction in the wet. New resurfacing technology is beginning to adjust how drivers may tackle wet conditions, especially on the newer circuits on the calendar. Formula One is unique to other motorsports in this sense - for every other road-racing discipline, the wet racing line should be respected in those slippery conditions, once again giving an opportunity for the best drivers to excel and outperform their opponents. It will be interesting however to investigate the development of wet weather racing as track surface and tyre technology develop in the coming years.
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