Why MotoGP's V4s dominated rain-lashed Le Mans

Danilo Petrucci spends his life dieting like a supermodel, but he’s a big man, so he’s still well over the ideal weight for a MotoGP rider. Except when it’s cold and except when it’s wet.

Which is why the swarthy Italian wore the biggest smile he’s worn all year at Le Mans, while everyone else shivered and cursed.

“I’m enjoying the cold weather a lot, for the tyres,” he said on Saturday afternoon, after taking his first front-row start since Mugello last year (which he also converted into victory).

A few hours earlier FP3 had got underway with track temperature at ten degrees, the coldest anyone could remember.

He races with his heart and his balls – and you need plenty of both when the rain is lashing down

Petrucci’s weight (he’s happy when he’s under 80 kilos, which is 15 kilos more than world champion Marc Márquez weighs) is bad for his tyres when it’s hot and dry, because extra weight equals extra load, which burns the rubber.

But when the rain comes down, that negative magically transforms itself into a positive, because the extra load he puts into the tyres generates much-needed heat and therefore grip.

That’s one reason Petrucci has always been good in the wet. And that advantage gives him confidence, which multiplies the advantage. Also, he’s a rider who races with his heart and his balls – and you need plenty of both when the rain is lashing down and you’re manhandling a 300-horsepower motorcycle around a racetrack.

Petrucci had one other important factor on his side on Sunday – he rode a Ducati. The Italian factory’s Desmosedici V4 has always been good in the rain. And eagle-eyed observers may have noticed that the top eight finishers at Le Mans all rode V4-powered motorcycles, with a Ducati, a Honda and a KTM on the podium.

Consider that last month’s San Marino GP – at grippy Misano – was dominated by inline-fours, with Yamaha’s four YZR-M1s and Suzuki’s two GSX-RRs locking out the top six positions.

How can this be – because surely the harder-to-handle V4s are even more of a handful in low-grip situations? Not necessarily, because a good wet-weather torque map can fix that problem and, anyway, the forces that riders put into the bikes are much reduced in the rain, so the livelier character of a V4 is somewhat damped down.

Perhaps most importantly, riders can’t carry much corner speed when the track is wet, so the best way to ride is in a stop-and-go style.

This is how V4s work at their best, while it doesn’t suit inline-fours so much. V4 riders can use their V-type cornering lines – dive to the apex, turn the bike and drive out – to great effect, especially since it allows them to work more heat into the front tyre during braking and into the rear tyre during acceleration. Meanwhile inline-fours riders find themselves unable to exploit their usual corner-speed advantage.

Of course, things are never quite that clear cut in motorcycle racing, so Petrucci had to use the V4’s point-and-squirt advantages but not overuse them.

“At the start of a wet race you never know how the grip will be, so I said, ‘Okay, maybe I will stop a bit more into the corner, to not risk too much, and pick up the bike in acceleration’, but I knew this would use the rear tyre too much,” said Petrucci, the seventh different winner from the first eight races of MotoGP’s weird but wonderful Covid-affected 2020 season. “But then the problem was that I was a bit slower in the corners, so I lost some tenths, so I tried to flow more, but still pick up the bike on the exits.”

Accelerating out of corners like this is great for the lap time and for heating the rear tyre, but it tends to overuse one part of the tyre, which is one reason why Petrucci and others struggled with wheelspin in the closing stages. Petrucci used that age-old trick to cool his tyres – he searched for the damp patches.

“Four or five laps from the end I had no more traction, so I tried to go more inside in the corners, where there was a bit more water, to cool the rear tyre. For sure my bike was really good in braking and acceleration – this was one of the few times that my weight helped me a bit so that I could use it.”