The single biggest factor influencing lap times and lap time consistency over the course of a day at the track is ambient temperature, which – naturally - is closely connected to track temperature and therefore tyre temperature.
According to Heinz Böse, an experienced racer but nowadays Operations Director at ATS (also South Africa’s representative for Dunlop racing tyres and therefore the de facto Dunlop Motorsport) the difference in grip when a slick or semi-slick race tyre is at 50 degrees versus 70 degrees can be as much as 15 percent in outright grip.
But as usual, bald numbers do not tell the whole story – something which I happily admit to, despite relying heavily on numbers generated by a VBOX datalogger.
As Martin Brundle said recently, statistics never had to drive a car into a corner. Unpacking that, it means the subjective stuff matters: when driving near the limit confidence in what’s under you is critical…it is fascinating to discover that it seems even a small drop in grip level can unsettle a driver.
The “top-gun” course at the AMG Academy gives students who have come up through the organisation’s ranks unfettered use of an AMG GT R, a car that boasts 430 kW and 700 Nm. The R Pro version – which is used for the flagship experience - is slightly lighter and has even racier aerodynamic appendages compared to the normal R. There are suspension revisions and more adjustability of the settings, and lighter 20-inch wheels. In the right hands, it can lap Zwartkops in about 65 seconds.
One of the stand-out drivers has been Russell Davidson and on his most recent visit to the Academy he set a chart-topping 1:08.5. Without diminishing his excellent performance – a combination of focussed coaching, a willingness to learn, and no shortage of natural ability – the planets did align to make the time possible.
It was late July which meant a cool ambient, yet the afternoon sun was still able to reach the tarmac directly. As a result, Russell had not only a consistent power delivery (heat make conservative engine management software intervene as soon as various temperature thresholds are crossed) but also a warm embrace between the rubber and the road, keeping the tyres in the zone.He took advantage of this.
VBOX data from his penultimate session that day shows that he was getting a peak lateral G of about 1.3.
A ‘G’ spike isn’t what we want to see when coaching of course – we want to see a driver keeping the tyres balanced on the edge of the traction circle for the entire duration of the turning process, and then transition it smoothly into forward thrust as soon as possible. That’s when we start looking at the “Combined G” field, one of the most useful features of the Racelogic’s Circuit Tools software.
But the point of this article is that in Russell’s final session of the day the sun had by then dropped lower and the majority of the circuit was in the shade and cooling rapidly. The grip level dropped like Francois Botha did after that short left from Mike Tyson, and in both cases, it was game over.
The fact that his nerve-endings were fully alert from an afternoon of track work and having just completed his fastest lap ever, he was perfectly attuned to the car. Within one flying lap, he knew – and on advice from the Academy’s Clint Weston in the passenger seat – that going faster could only be achieved by taking much bigger risks. While the drop in maximum grip generated wasn’t huge, the car felt considerably edgier.
This was a perfect case of the subjective making the decision for a driver, who acted on the subtle messages from his various senses. The VBOX data confirmed that grip had diminished (affecting braking and cornering) but only to about 1.25 G and that there was a clear reason why they were not able to repeat their earlier form.
Next time you’re at a track and you’re wondering why things don't feel quite right (and may have felt great earlier), take a step back and consider all the factors. Of course, if you have a VBOX fitted you’ll be able to investigate and compare and come up with a fact-based answer.
Concludes Böse: “If there is no good reason for being slower, maybe you just need to put your Big Girl Panties on, and give it another go – this time with more pressure being exerted on the right-hand pedal!”