Pirelli introduced new 18″ Formula 1 tyres in 2022, and while “porpoising” might seem to be the most talked about issue teams are facing, tyre graining is also causing a headache as this Tech Draft will show.
It is widely acknowledged that the biggest technical challenge that Formula 1 teams are facing early on in, and because of, this new era of technical regulations is the big bounce, or “porpoising” as it is more colloquially known, and any resolution is key to improved performance as the season progresses.
However, in 2022, tyre graining is another technical battle many are fighting, once again due to the new regulations, and if not managed effectively it can have a catastrophic effect on a car’s race performance.
Graining is probably the most common tyre defect that drivers and engineers deal with in F1 and is visually identified on the tyre tread surface as a ripple effect in the rubber caused by very small tears in the surface of the rubber. It is facilitated by bits of rubber separating and tearing away from each other and then melding back together because of the high tread surface temperature.
The result is an uneven tread surface and a compromised compound that reduces grip especially in corners and under braking, essentially an unstable layer between the tarmac surface and the tyre contact patch. Friction with the road surface overheats the contact patch and radiates that heat into the compound, and works into it.
Quite often the cause of graining is oversteer and understeer as the contact patch is dragged in a particular direction and scrubbed, overheating the compound and causing it to shear and grain.
Cause of graining can be identified by visual inspection
It is worth mentioning that most experienced engineers, and even some drivers can identify the cause of graining on visual inspection.
For the first Grand Prix of the season in Bahrain, even though the expected lateral loads an F1 car would experience there are not overly high, it was hardly surprising that because of the circuit’s well known abrasive surface, Pirelli selected to supply the teams with the three hardest tyres available, the C1, C2, and C3 compounds.
That selection seemed to work well enough, but even after the previous three-day pre-season test there the week prior, a few teams still suffered from graining, particularly on their longer race runs on the C3 Pirelli compound.
The following week in Jeddah F1 teams were given the option of selecting their weekend allocation from a range one step softer with the C2, C3 and C4 compounds offered. Retrospectively, it was hardly surprising that the less abrasive surface coupled with some higher lateral loads resulted in many teams experiencing graining.
The compounds offered at the last round at Albert Park were intriguing given that as in Jeddah, the C2 and C3 compounds were available, but rather than offering the C4, it was another step harder in the C5 that was available.
Williams excelled in managing graining in Melbourne
Nevertheless, even though that additional step harder was on offer, many teams still battled graining, except for Williams who excelled with a one stop strategy in the race for Alex Albon who started on the C5 and boxed on the last lap for the C2 to satisfy regulative obligations and finished P10, which was a remarkable finish for him and his team, given its recent race form.
Several factors have widely been attributed to F1’s apparent sensitivity to graining such as the 18” tyres’ lesser sidewall compliance, stiffer suspension settings due to ground effect aerodynamics, and the fact that a ground effect car has a greater propensity to understeer with the resultant front tyre scrub as a result.
But there may very well be a time in the near future where a re-set of the expectations of the Pirelli compound’s behaviour happens because the way things are at his stage of the new era, it is a status quo in that mastering the sensitive nature of tyres has a proportionally large influence on race results.