The bumps are back. Ducati rider Danilo Petrucci said after Free Practice 2 on Friday at Circuit of The Americas that the waves in the long straight were putting his factory GP19 engine repeatedly into its rev-limiter.
“I was afraid that too much on the limiter would break my engine.”
Moments later, we were crowding around Maverick Viñales, and I asked him if this was happening to him as well.
“Yes,” he replied simply. The Yamaha rider went on to say, and demonstrate with his arms, that the front of his machine reared up at each wave. When the front end extends rapidly, the ECU thinks it is a wheelie in progress.
“There are not only waves,” he said, “there are bumps.” He made chopping movements with one hand. “But the grip is better this year.”
We know this well-appointed and much-admired track—all the riders say they love to come here—was once again surface-ground, just before this year’s IndyCar event. Yet the riders gave detail after detail of where and how bad the surface waves and bumps are. And that, although the unevenness on the straights is a problem, similar features in corners are even more difficult to deal with.
Viñales then observed that he is fortunately competitive and that his setup has room for improvement, making him optimistic for Saturday’s qualifying.
When he said, “I can ride these bumps,” Viñales was asked, “How? By locking your arms?” He gave a “Who knows?” shrug and said, “Maybe because I am strong.”
Aleix Espargaró’s Aprilia produced violent full-lock steering motions on the straight that broke his bike’s lock stops.
Perhaps this can be fixed, but it would not be simple. The reason is that this track is alive, that it moves and undulates constantly. This makes exercises such as surface grinding into Band-Aids. This may also explain Viñales’ observation that traction is better this year.
What do you do when the abrasive grains on the work surface of a grinding wheel have become dull? You “dress” the wheel; make a pass across its surface with a super-hard diamond wheel dresser, exposing fresh, sharp grains. This may be the origin of the improved grip Viñales described.
This is despite the most well-advised and careful preparations made when the circuit was first built: digging down 8 feet and backfilling with a heavy gravel base to provide excellent drainage. My colleague Matthew Miles saw the track during its construction, the trenching for this backfill.
The flatness of the surrounding land and the heavy clay base suggest this was once a shallow sea, a settling basin for fine river-borne sediments. Clay particles consist of stacked tiny flat mineral plates. The familiar Speedy Dry and kitty-litter products are expanded clay, whose ability to absorb liquids, which wick into the spaces between the plates, is so useful.
In the soil under COTA, it appears that the clay expands where the soil is moist and contracts where it is drying, conditions that change with changes in the distribution of groundwater. If 8 feet of gravel have not stopped these movements, what can? Assuming that soil-dynamics engineers directed the original measures taken in building this track, who is to be consulted now?