How to make an F1 car fast in the wet

Friday at Suzuka was the first time since the current V6 hybrid engine formula arrived in 2014 that we've had a first day of practice in F1 with absolutely no dry laps completed whatsoever.

The weather is expected to improve dramatically through the rest of the weekend, which potentially renders today's efforts at Suzuka meaningless in the grand scheme of things.

Certainly world champion Lewis Hamilton thought so, asking reporters whether they knew the phrase 'diddly squat' when responding to a generic question about what he'd learned from venturing out onto the circuit in his Mercedes.

But even in such foul and unrepresentative weather, there are still significant variances in performance between the different cars, so perhaps it is still possible to learn some information about the competitive order, and figure out what makes one Formula 1 car faster in the wet than another.

Hamilton felt he learned "diddly squat" from Friday at Suzuka © LAT

It's often said that wet weather is an equaliser, which reduces the driver's dependency on a good car to be quick. To some extent that is true, but in fact F1 cars are so reliant on downforce to make them work properly that actually wet weather can give quite a fair indication of who's got a good car aerodynamically and who hasn't.

Teams will not run with bespoke wet aero packages, but they will run their cars with more downforce than they would in the dry.

"You run more downforce in the wet - not necessarily the maximum, but there's a different optimum and it's always higher," Lotus head of trackside operations, Alan Permane, tells AUTOSPORT. "You also move the aero balance rearwards, which makes the car more comfortable for the drivers."

The aim is to stabilise the back of the car under braking and on corner entry, so the driver can feel confident enough to lean on his machine. Teams will generally reduce the angle of the front wing to achieve this effect, which will reduce front grip relative to the rear. They generally avoid adding rear wing, because this introduces extra drag, which will penalise the car on the straights.

"If you trust your rear on turn-in it means you can brake later and turn in sharper, and normally things go well from there," says Lotus driver Romain Grosjean. "The driving style doesn't change dramatically. It's still the same braking shapes, throttle application is still the same shape; everything is a bit more smooth, and I put less pressure on the brake pedal.

"Depending on the amount of grip you have on track it's a bit more about the steering wheel, where you can see some drivers hitting it harder than others, and the confidence you have, [but] it doesn't really change from dry."

However, some drivers do prefer a different style from dry to wet. Sauber's Marcus Ericsson says he doesn't mind the rear of the car being unstable under braking in the dry, but in the wet he prefers it the other way around and to do more work with the steering wheel - or "hit it harder" as Grosjean puts it.

F1's current parc ferme rules, which prevent teams altering the set-up of their cars between qualifying and the race, means drivers basically have to get used to driving a car that is optimised for the dry when conditions turn bad, making only small adjustments to engine, differential and brake settings from the cockpit, and trying to cope as best they can.

Adjustments to the differential will again be aimed at stablising the rear end of the car, so the driver has confidence to push harder into the corners. 'Softer' engine and gearchange settings can also be used, to improve traction, but these come with a cost in performance, so drivers will be encouraged to regulate with their hands and feet where possible, rather than relying on electronics.

Brake bias is usually transferred rearwards in the wet, but the influence of electronic brake-by-wire systems on current F1 cars reduces a driver's feel for the rear brakes, therefore they must retain more front bias and use their skill with the brake pedal to avoid locking up the fronts, which is more likely to occur on a low-grip wet surface. Teams also use tape to blank off parts of the brake ducts to help generate temperature for wet running - and these are easy to remove quickly if conditions improve.

Major set-up changes are rare, but teams do adjust downforce for the wet © LAT

Potential mechanical changes, such as softening the suspension and the damping, might be considered if a full wet weekend was guaranteed, but they represent too big a risk if conditions were likely to change back from wet to dry, so are usually avoided.

Permane adds: "Softening the suspension overall? Possibly, but these cars are set up so much more aerodynamically than mechanically. So you're unlikely to change springs; you might change roll bars, but you're still chasing performance through aerodynamics."

Teams don't generally want to introduce adjustability onto their cars' suspension either, because that would mean the penalty of extra weight carried over in the dry, so again it becomes a game that is focused on the overall aerodynamic performance of the car, with compromises accepted in terms of suppleness, its effect on traction, and the car's ride over the bumps and kerbs.

PURE PACE RANKING (WET)
1. Red Bull (Kvyat) 1m48.277s
2. Mercedes (Rosberg) 1m48.300s
3. Toro Rosso (Sainz) 1m49.434s
4. Ferrari (Vettel) 1m50.268s
5. Sauber (Nasr) 1m50.968s
6. Lotus (Maldonado) 1m51.557s
7. Force India (Hulkenberg) 1m51.674s
8. McLaren (Button) 1m51.861s
9. Williams (Massa) 1m52.765s
10. Manor (Stevens) 1m58.059s

There are some vagaries here, but the first four cars are ranked in the order many in the paddock would argue is representative of the quality of the chassis produced by each of those teams this season.

The midfield order is more surprising. Although the Sauber C34 has been substantially updated aerodynamically recently, you would certainly not yet expect it to match the normal level of a Force India, or a Williams in the dry.

The FW37 performs poorly at slow speed, and also in the wet, even though it is a strong car in dry conditions - certainly one of the top six on the grid. But that's when engine performance comes back into the equation, the effect of which is reduced dramatically in the wet.

"Some cars just work better in the wet and some work worse," reckons Permane. "Toro Rosso a couple of years back used to leap up the timesheet in the wet.

Williams is making slow progress on resolving its issues in the rain © LAT

"They probably don't know why. My feeling would be it's almost certainly related to aero. The intermediate and wet tyre are a different shape [to the dry tyres], and tyre shape has a massive impact."

This is because all teams are working hard to use their aerodynamic devices to scavenge airflow that would otherwise wash out around the tyres and channel it back towards the diffuser, to generate downforce.

Permane's contention is the profile of Pirelli's wet-weather tyres upsets this process, thus reducing downforce in certain places and potentially creating inconsistencies.

Teams could theoretically devote precious windtunnel time to better understand and minimise this effect - but this would represent a poor use of limited resources, given that the current rules restrict windtunnel use and prevent set-up modifications between qualifying and the race. After all, there is little point devoting time to an aero phenomenon that occurs rarely (wet races are not common), and does not translate equally to the profile of the dry tyres.

Williams is still trying to understand exactly why its car struggles so badly in wet weather relative to the dry. There is a suspicion that perhaps the diffuser is stalling when running through water, which creates inconsistency in the amount of grip the car can generate from corner to corner.

Certainly Valtteri Bottas, who sat out FP2 to save his wet rubber, reckons aerodynamics is at least part of the reason Williams has difficulties in the rain.

"We are struggling with the balance, and in practice one we split the cars with very different set-ups," he explains. "I think we found something. Not a breakthrough, we still have more things to learn in the wet, but it's a balance thing and an overall grip thing.

"Normally understeer has been the problem, but we improved it slightly. We are looking into it. The car is made for dry conditions. I can't say much more really, we still need to look at everything and learn more. Cornering in general, that's the main problem."

If the driver doesn't have full confidence in the balance of his car, or its ability to generate grip through the downforce it produces, he will struggle. It seems that is as true in the wet as it is in the dry.

Tyre management is also crucial, because the wet rubber is still prone to overheating on its surface if the car slides too much. The full wet tends to hold up better than the intermediate, but it also tends to be a slower tyre - until the track becomes so wet the depth of the intermediate tread can't cope with the volume of water, the tyre loses all contact with the road, and the cars begin 'aquaplaning'.

We also heard McLaren's Jenson Button complaining over team radio about "graining" his front tyres during FP2. If a car develops too much understeer it will overheat the surface of the rubber and cause it to tear apart. Once that happens you lose grip, and you're unlikely to get it back until you let the tyre cool down then generate more bulk temperature to gain more grip and stop the car sliding, or you change the tyre altogether.

But if a car is balanced well, and can retain strong aerodynamic performance when it transitions from dry to wet conditions (and thus from dry to wet tyres), the driver is more likely to gain the confidence he needs to lean on it and go fast.

Sainz was able to shine on a good day for Toro Rosso at Suzuka © LAT

Toro Rosso rookie Carlos Sainz Jr had never driven at Suzuka before this weekend, yet such was his confidence in the aerodynamic performance and balance of the STR10, that he was able to set the fastest time in FP1.

"I keep the basics [of my driving], but I change the lines, the braking, the steering inputs quite a lot - it's a training that comes from my first year of single-seaters," he explains. "With a Formula 1 car it's even more challenging because you have more power, so you need to make the corner a bit more of a 'V'. You need to really make sure you have the car straight when you go on the power because you have 800 horsepower there.

"Braking is very difficult, because you spend much more time on the brakes, so there's much more time to make a mistake. You need to have trust in the braking. My first taste in the wet was in Austria and I already felt really good there, setting some good laptimes. When I saw the rain today I thought we could have another good day."

Sainz is undoubtedly a fine driver, but it's also the quality of the Toro Rosso chassis that has allowed him to perform so well in the wet. Low grip conditions such as those at Suzuka on Friday mean less of an engine's performance can be directly translated to laptime, which means there is less of a variation between cars with different power units than there normally is in the dry.

In this scenario, it seems the current engine-dominated formula reverts to being more about aerodynamics. One of the reasons Mercedes has dominated F1 over the past two seasons is the strength of its aerodynamics and its engine. Red Bull dominated previously because of its aerodynamic prowess.

Perhaps it was no surprise these two squads topped the times in FP2, and that just 0.023s separated the best cars from each. If the rest of the weekend is dry, it's unlikely to remain that close.