Just why are the Hankook all-weather tyres so sensitive to pressure changes in different racing conditions on the Gen3Evo cars?
It’s a question asked by many fans and TV viewers. It has offered up fascinating races throughout the last few season but the two most recent ones are clearly Tokyo last weekend and the second Shanghai EPrix last month.
The tyres are strictly prescribed by Hankook with a maximum and minimum pressure: 1.20 bar minimum and 2.70 bar maximum front and rear.
Overall, the sensitivity in pressure changes within those windows is up changes is that the base compound is super sensitive to temperature fluctuations.
“The compound just doesn’t like the cool track temps and it’s the same reason you see lots of build laps even in the dry,” Formula E TV analyst and the VP of product at the data technology company Paceteq.
The high pressure reduces the contact patch which increases the load over a smaller area and generates more temperature in the tyre. As the circuit dries, this then overheats the compound and affects the pace severely, added Lau.
As all-weather tyres the rubber must work in every conditions from rain to 60 degrees of track temp. Where the Gen 1 and Gen 2 Michelin product was always working, whatever the conditions without having to change too many things, with the Hankook product it is very different challenge for the teams and driver.
To work in the dry the teams have to go extreme with pressures and for the wet they likewise have to go extreme too but in the polar opposite direction, with up to 1.6 bar difference.
“It was all about weather and tyre pressures today,” Mahindra’s Edoardo Mortara told FEN. “ It was a similar situation to Shanghai – when you start from the front and it’s wet, the safest is to start with the rain pressures.
“It didn’t work, and after 10-15 laps you feel like a sitting duck because there is a big difference if the others have lower pressures. It was not our day. You need to have luck at some point in order to do well in this championship and these last three, four weekends have been tough.
Asked how the decision is made, Mortara said that “you try to check the weather forecast, but it’s difficult to forecast the conditions here in Japan for whatever reason, and you can have big changes very quickly.
“The team decided to split strategies and in the end it worked out because we had one car that won, and personally for me it didn’t. It is what it is. It’s motorsport I guess.”
The crossover points were very visible yesterday on Sunday in Tokyo, and it was clear how the tyres were challenging at certain points of the race. If you are not in the good window the pace difference per lap is several seconds as was seen when the crossover point of the race was reached, around lap 26 although by then the wet weather pressured drivers had long since been hurting.
To make a good choice, the teams essentially bet that the track is coming to them, which is what many teams were doing in Tokyo yesterday.
Yet it is not done by scanning the skies, licking and sticking a finger in the air. Process, methodology and science is crucial and teams will have had meteorological forecasts in addition to track temperature, quantity of standing water, rain fall characterisation studies ongoing, and especially how quickly the track was drying.
Sometimes the team get it right, and they are the heroes, other times it’s the wrong call and they are the villains. It’s just how such a crucial call goes when the tyres are that temperature sensitive.
“We’ve made all the wrong decisions this year, but credit to the team today,” Oliver Rowland told FEN after finishing a strong fourth.
“After Shanghai they went away and did a lot of work, we came here with a plan and we executed it. Norman was slightly different to me, and would have come at the end. I think on the spectrum [of wet vs dry] we were about right.
“It was safe, not too high risk, which I think in our position was the right thing to do.”
