Red Bull looks good as Mexico pushes limits

Formula 1 won't face a bigger technical challenge this season than it is currently tackling at this weekend's Mexican Grand Prix.

The Circuit Hermanos Rodriguez is 2200 metres above sea level. That's 1400m higher than the next highest venue on the F1 calendar, Brazil's Interlagos circuit.

That basically means everyone is short of breath in Mexico. The air is so lacking in oxygen content relative to other tracks that all the usual set-up parameters are thrown off, and the cars behave quite differently to elsewhere.

The 'thin' air at this altitude means the engines must work much harder, specifically the turbo, to produce the usual power outputs, while also making it much harder to cool them down, because you get less effect for the same volume of air through your cooling ducts compared to sea level. For the same reason, brake cooling is also a massive challenge.

Looking at the basic layout of the rejuvenated 2.674-mile circuit on the outskirts of Mexico City, you would expect teams to face a headache deciding how far to compromise straightline speed in sector one (which features two significant straights) with downforce and grip for the high-speed esses in sector two and the tight twists of sector three.

Red Bull found a good compromise on Friday © XPB

But all teams run maximum downforce here, because the lower air pressure means the cars do not get near exploiting the full potential of their aerodynamics, and also face minimal air resistance.

That means they travel faster down the straights, which puts extra strain on the brakes, but also means there is less grip available for the corners...

"Everything works against you unfortunately," Mercedes technical chief Paddy Lowe told Autosport before practice began.

"There is more heat from the extra [air] compression, there's less retardation at the end of the straights, more brake heat and less air to cool them.

"We're running the wing levels of Monaco, but getting less downforce and drag than Monza!

"Turbos will be pushed on reliability. It will be a big challenge. I think we'll see a few problems - hopefully not for us!"

Unfortunately for Lowe, Mercedes did encounter problems, when Nico Rosberg's rear brakes caught fire spectacularly in the first practice session.

Rosberg demonstrates Mercedes' cooling challenges © XPB

Mercedes is often a little marginal on cooling with the W06, and many times we've heard the team warn its drivers about brake temperatures at regular circuits.

The problem, of course, is that 'opening up' the bodywork and increasing the size of the brake ducts to aid cooling will cost the car aerodynamic performance, which means less grip available to the drivers.

The slippery nature of the revised circuit also requires higher tyre pressures to generate heat in the tyres, and thus requires the compromise of a smaller contact patch with the track, which means even less grip!

This is probably why we saw so many mistakes (and a few crashes) on Friday, and why Lewis Hamilton found the slipperiness of the circuit so "crazy".

"The biggest issue is the cooling, because the air mass flow is not the same," McLaren racing director Eric Boullier tells Autosport.

"You have some special brake ducts for here, [but] because of this trickiness of the cooling, the loss of performance you get compared with the cooling, and the fact you have less downforce, it is actually even more complicated, because you design a car for most of the races, but here you have to change your cooling, which damages your performance, just to be able to run."

Morning pacesetter Max Verstappen crashed early in the afternoon - one of many errors through the field © XPB

The engines are working harder because the turbos are revving harder (Honda was at the maximum 125,000rpm limit and Renault estimates its unit is turning 8-10,000rpm faster than usual), so you have more heat to deal with, so you need more cooling, but that takes away downforce, which takes away grip, which makes it more difficult to slow the car down, and to drive it quickly through the corners.

Surely the toughest technical challenge of the year by far for F1?

"Yes definitely," adds Boullier. "The top speed is higher than Monza, so the braking zones are longer, you use your brakes too much, but you need to cool them more, it's like a vicious cycle."

This should at least produce an exiting spectacle for the thousands of Mexican fans due to turn up on Sunday. There was a great atmosphere around the place, as many more spectators than is usual for a GP Friday showed up to cheer on home hero Sergio Perez.

The unusual atmospheric conditions, combined with the general lack of grip coming from the new track surface, also played a large part in partially mixing up the order here.

PURE PACE RANKING

1. Mercedes (Rosberg) 1m21.531s
2. Red Bull (Kvyat) 1m21.776s
3. Ferrari (Vettel) 1m21.984s
4. Williams (Bottas) 1m22.721s
5. McLaren (Alonso) 1m22.993s
6. Force India (Hulkenberg) 1m23.290s
7. Lotus (Maldonado) 1m23.363s
8. Toro Rosso (Sainz) 1m23.364s
9. Sauber (Nasr) 1m23.430s
10. Manor (Rossi) 1m25.940s

Mercedes still topped the times, but both Red Bulls were able to split Rosberg from newly crowned triple champion Hamilton.

The top order looks very similar to Hungary, where Red Bull was able to get into the mix with Ferrari in qualifying and McLaren was also much improved relative to the opposition.

McLaren is in better shape in Mexico © XPB

But the track is evolving very fast. Jenson Button joined the action late owing to a loss of his ERS deployment (not engine related and thought to relate to a switch setting), but set the ninth fastest time of all on the medium tyre while the rest were completing long runs on the soft, despite Pirelli estimating the medium tyre to be two seconds slower than the soft on Friday...

"When you have an oily asphalt and no grip, cars with more downforce are favoured compared to ones with less," says Boullier.

"This is why you have a change of the order and you see us in front of Lotus and Force India. We have more downforce than them.

"The more the track will get grippy the more these cars with the powerful engine will recover some pace. Plus the fact they have some [extra] power during qualifying. We haven't seen that yet.

"It's nice to see some signs of improvement but I don't expect to be eighth and ninth tomorrow; 11 and 12 maybe, but not more."

Attempts were made at longer running on the soft tyre by all teams, but with vastly varying success in terms of consistency and stint length in gradually worsening conditions as rain began to fall, so this is difficult to read without eliminating a large number of outlying laptimes.

LONG RUN RANKING

1. Mercedes (Rosberg) 1m24.584s (4-lap average)
2. Ferrari (Vettel) 1m24.632s (3-lap average)
3. Red Bull (Ricciardo) 1m24.637s (2-lap average)
4. Williams (Massa) 1m25.092s (5-lap average)
5. Force India (Perez) 1m25.408s (5-lap average)
6. Toro Rosso (Sainz) 1m25.611s (7-lap average)
7. McLaren (Alonso) 1m25.865s (4-lap average)
8. Lotus (Grosjean) 1m26.142s (2-lap average)
9. Sauber (Ericsson) 1m26.193s (3-lap average)
10. Manor (Rossi) 1m28.494s (3-lap average)

Once we do this we get a ranking broadly in line with what you would expect based on recent form, although with Red Bull definitely more competitive on a circuit that suits the RB11's strengths in high-downforce specification through low-speed corners in particular.

Whether it can genuinely challenge Mercedes and Ferrari in the race will depend on how much extra pace the W06 and SF15-T find in qualifying, and how much performance they have to give away to maintain reliability in the race.

But on a tough and slippery circuit, with cars that are difficult to drive and running at their limits, anything could happen...