Álex Márquez, after his brother Marc fell on lap 3, knew there was opportunity for the taking, even though he remained where he’d started, fourth, for two laps. By lap 3 the order was Quartararo, Bagnaia, and Álex. Some have hailed those early laps as “race of the century” level. But we know that experienced riders accept extra risk for the great prize of leading rather than overheating the front tire in the hot draft of others.
Álex told it: “Everybody today wanted to be in the front because it was so important for the front tire, and everybody was a bit crazy in that first corner, that first lap. In turn 1 I had contact with Marc; I was trying to make the move on Marc to the inside. I was not sure what would happen with my front as I was a bit on the limit.
“When Marc lost the front, I was saying inside my helmet, ‘Nooo!’ because he was trying to save it for a long time, and then he disappeared.” He remounted to finish 12th.
Fabio Quartararo was pushing all weekend because there was something worth pushing for: his factory Yamaha was working well at Jerez, allowing him to set pole. He crashed in the half-distance Saturday sprint but was nevertheless delighted to be in the thick of it—he’d led the first lap but crashed out.
On Sunday he emerged from the post-start tussle in first, and stayed there for 10 laps, then was passed by Álex Márquez.
Pack up your picnics, folks, and head for the car park, for that’s how the top five stayed to the finish. Why no cut-and-thrust excitement every lap, to a nail-biter finish?
Francesco Bagnaia (factory Ducati, third) tells us why: “Only in the first three or four laps, I felt good on the bike. Then I never had the opportunity to be able to overtake Quartararo. The problems are always the same. When you are behind another rider, the front tends to lock up. Today Marc was not in front of everyone, and the same thing happened to him.”
The hot slipstream of the bike ahead heats your front tire, so its pressure rises. That causes its footprint on the pavement to shrink, reducing grip enough that locking occurs during braking. Riders were also falling at brake release during corner entry: the moment when front tire footprint shrinks as load is reduced.
Bagnaia had this problem in the sprint. “Every time I arrived in turns 7, 8, 11, 12 I was losing a lot, the front was locking a lot and I was losing it everywhere.”
Maverick Viñales (Tech3 KTM, fourth) suffered the same. “I had a really good pace. I was even recovering on Pecco and Fabio in the end, but then I started to miss the apex all the time, so I calmed down a bit and told myself, ‘Fourth is OK, Maverick, let’s try next time.’
“I closed the gap to them but every time I got too close it was so hard to stop the bike. So then I’d drop back, the bike would work well again, and I’d catch up. Then I’d get close and have to drop back again.”
In the end, it comes down to what pace each rider can maintain (and still have enough tire to reach the finish), so at the end, Quartararo was a second and a half back from Álex, Bagnaia was six- to seven-tenths behind him, and Viñales another second and a half from him.
It has been pointed out that Marc’s crew may have assumed he would be up front in the cool air, and so gave him a squeak of extra front tire pressure as insurance against being sanctioned by the office workers who enforce Michelin’s tire pressure rule.
Of his crash, Marc said, “At Austin I understood why I crashed, but today I don’t understand. I need to analyze it because I was not attacking, I was cruising…because I know that the second part of the race is my strong point.”
So many times we have seen him conserve rubber while staying close to the front, then making a late move to win.
“I didn’t check the data, but maybe I was one degree more [lean] angle.”
According to Luca Marini (Castrol Honda, P10) there are two kinds of rear tire “vibration.” He said, “It always happens to us. In my opinion it is the fault of the grip at the rear. When we have more of it, the vibration will…decrease.
“It is the exact opposite of the KTM. They suffer because they have too much grip.
“…as soon as the grip is poor, we slide the rear and the bike begins to vibrate.”
Classic chatter tended to occur most under conditions of good grip and heavy load (the tire transmitting a lot of force). Yet here is Marini’s Honda, chattering more with less grip.
Often there is an epidemic of chatter when a tire’s stiffness is reduced a bit in an effort to spread out a larger footprint. If the tire were infinitely thin and flexible, it would spread out against the pavement until the footprint area, multiplied times the inflation pressure, equaled the load carried by the tire. The true footprint area is less because the tire must be stiff enough to bear the loads passing through it without buckling or losing directional stability (this is why radial-ply tires must be stiffened by tread belts and sidewall chafer plies). There is also some history of more flexible tires having heightened ability to oscillate (vibrate, chatter—pick the word you prefer). The two examples before us are the classic side-to-side movement of the whole belted tread, known before 2000 as “chatter,” and higher oscillatory modes such as the wobbly nutation of the whole tread band as seen in the wild video of Jack Miller in action. More mystery to be solved!
Speaking of mysterious, how did Viñales elude the vibration? He said they’d tried a mass damper at Argentina and Texas but took it off. And in Monday’s official MotoGP test Viñales was second, 0.361 second behind Marc Márquez, and ahead of the Yams of Quartararo and Álex Rins.
Now let’s consider what’s influencing front tire grip. We’ve already mentioned that increasing inflation pressure reduces footprint area and grip. Tire pressure rises with a rise in air or track temperature—an oft-cited example is day versus night operation at Qatar, and in any case, afternoons tend to be warmer than mornings.
Then there is heating from being in the hot slipstream of a bike ahead, as described in paragraphs above.
Next, the tread rubber compound itself. Grip is a function of hardness (a “soft” tire may give more grip, but there are exceptions!) and of tread temperature.
If we progressively lower the temperature of a sample piece of rubber, it eventually congeals into a solid; this is the glass transition temperature, or Tg. If we now raise the temperature, the rubber becomes more flexible but its grip is low because it’s still too stiff to conform well to the pavement it is sliding against (this is why it’s dangerous to go out on cold racing rubber). In a certain range of temperature, conditions are just right and the rubber’s grip is at a maximum.
Further temperature increase makes the rubber more flexible but with less internal damping, so grip falls (this is grip loss from overheating).
As with so many natural phenomena, you can have a lot of some desired effect in a narrow range or less over a wider range. You can even formulate your compound to deliver very high grip over a range so narrow that a modest change in the weather makes the tire useless on that day. Tire tread rubber compounded for production vehicles has much lower Tg so it gives useful grip over a wide winter-to-summer range.
It’s good to see that Yamaha and Honda are continuing to recover from their slumps. The Yamaha worked for Quartararo at Jerez, but may suffer a role reversal with Honda from the different nature of the next track on the schedule. KTM and Honda continue to suffer crippling rear tire vibration but there were KTMs in fourth, sixth, seventh, and ninth.
Honda looked unstoppable for years with Marc Márquez, but now Ducati is on top. Before that, Yamaha and Rossi dominated. Ducati was mostly nowhere after its 2007 triumph with Casey Stoner—until their recent dominance, which is hard-earned.
Have patience! Surprises are coming. The clever people at work in the several teams will see to that.
The next many-dimensional battle is Le Mans, May 9–11.
Here are the current points standings (lots of racing left, so don’t despair):
Álex Márquez - 140
Marc Márquez - 139
Francesco Bagnaia - 120
Franco Morbidelli - 84
Fabio Di Giannantonio - 63