Audi Sport Team Abt’s Lucas di Grassi has explained for the first time the reasons why his car was found to be underweight in post-race scrutineering that cost him an ePrix victory in Mexico City last month.
A time-consuming battery problem inadvertently led to a miscalculation by his team's engineer – coupled with high tyre wear and the need to run aggressively to beat the dominant Renault e.dams car – was enough to make his Abt Schaeffler FE01 fail the minimum weight of 888kg by 1.8kg.
"Every race we're very close to the weight limit to catch Renault," di Grassi told Motorsport.com. "We did an analysis after. The true story is that the car which was disqualified, the first car, was underweight – the second one was right on the weight limit.
"We had a battery problem at the very beginning from Free Practice 1 on the first car. And the Williams guys were repairing that battery on the car for the whole day. That car was only ready one hour before the race, so there was no time to re-evaluate the weight of the car.
"And because you need the belts and some other components – we changed the belts from one car to another, and the engineer didn't take this into account.
"So it was a very small miscalculation, and we also had very high tyre wear, much more than we expected, which added up to 1.8kg underweight.
"The other car was fine, and that was the car we did qualifying with. It was very strange, they're effectively the same car, same components, same amount of ballast that we run every year. And the night before it was on the weight target. And it's not like I sweated more, or had a different weight for the weekend."
Different circumstances to Berlin exclusion
It is the second time in the space of a year that Di Grassi has lost a maximum points score after he was also denied a win at the Berlin ePrix last May.
On that occasion the team was penalised for modifying a portion of the front wing and wheel fairings on its car – about which he is still clearly angry.
"Last year I lost the championship because of this," added di Grassi. "The rule is the rule, you have to accept it, but last season's disqualification for a badly-made repair on a part that has no affect on performance whatsoever, for me was completely wrong.
"This was a very small team mistake – and even though I won by 6s so a kilo would not have made that much difference, but I accept it – we have to follow the rules."