Formula 1's technical chatter this year has been dominated by talk of tires, with all outfits realizing that a good weekend and a bad weekend can rest heavily on getting their Pirellis into the right operating window.
Engineers are well known to find perfection in all aspects of car design, and much of the tire focus this year has revolved around pressures, which prompted some deep investigation from the FIA about what outfits were up to amid suspicions that some were manipulating the levels.
Such were the levels of concern that in the end the FIA decided to act, first demanding teams log live tire data from Monaco and then, from Austria, changing the way pressures are checked.
Having had two grands prix under the new rules, have the new checks exposed what teams were up, or have they merely opened up more intrigue?
The FIA has been taking note of an expansion of tricks employed by the teams to control tire temperature, following the introduction of measurement of the starting pressures on the grid in Monza last season.
This came as a result of the tire failures at Spa, with higher pressures ensuring there could be no issues with the structural integrity being weakened by teams taking it to the limit.
That first race prompted a post-race investigation into the cars of Lewis Hamilton and Nico Rosberg, whose tires were found to be under the minimum limits on the grid. However, a debate about when the readings were supposed to be taken meant the team was cleared of all wrongdoing.
Although no teams have been found to be below the limits since Monza, it has not stopped suspicions that some teams had found ways to keep pressures the same – or even lower them – once the readings on the car had been taken.
The action taken in Austria – of taking the pressure readings before the wheels were mounted to the car - was aimed at removing the possibility of the teams introducing more heat to the tire when mounted on the car.
In theory this would increase the pressure for the measurement, before rapidly cooling brake components would reduce the tire pressure during the formation lap. This would give a competitive advantage over those with less mature solutions, or none at all.
A long time coming…
Tires are hugely important, as they offer better mechanical and aerodynamic performance if handled correctly. Get longer life from them too and it helps with strategic options as well.
Finding technical nuances in a tire's make-up, which a rival does not have, can yield several tenths of a second per lap and improve tire life over a stint. This is invaluable when we consider the development cycle of an F1 car.
What initially appears to give small gains snow balls as the development focus on the rest of the car is pushed in the same direction.
Mercedes has been at the forefront of this battle and, through the harsh lessons of its early years back in F1 plus Singapore last year, it has developed various solutions to improve tire performance.
For anyone that is new to the sport you’d do well to know that, while Mercedes dominance of the turbo hybrid era is impressive, what is more so is its turnaround in fortunes when it comes to tire management.
It struggled to deal with the thermal degradation of the Pirelli tires when the Italian tire manufacturer first came back to the sport in 2011, often providing its drivers with a reasonably quick car but one that suffered to manage the tire's life over a stint.
Lessons applied then are clearly being applied now.
In F1, increased restrictions simply means more inventive solutions need to be found, something that came to a head again at Monza in 2015, following scenes at the previous round at Spa that echoed what we saw at Silverstone in 2013.
Once again the drivers were critical, questioning the quality of Pirelli's product, but once again there seemed to be an underlying factor that needed closer scrutiny.
Pirelli traced the issue back to low operating pressures (used by the teams to improve performance), combined with the high vertical and lateral loadings through Eau Rouge which led to the formation of the standing waves that can be seen in the image above.
Standing waves are when the tire deforms irregularly and then tries to recover to its original shape and state. This in-turn increases the bulk temperature and pressure within and can be catastrophic to the life of the tire.
This, along with a flagrant disregard for track limits, led to several tire failures, which included Nico Rosberg and perhaps most famously Sebastian Vettel (above).
In order that the situation at Spa wasn't repeated, the FIA and Pirelli began checking the starting pressure of the tires on the grid at the next round in Monza.
Following the introduction of this new procedure, Mercedes reacted almost immediately, especially as it's thought that it had a debilitating impact on its performance in Singapore.
By the time Formula 1 landed in Japan, Mercedes had a new solution, utilizing the reflective jacket you can see in the illustration above.
This jacket was placed over each brake drum and a blower connected to heat up the brake drum, disc, and other ancillary components.
It means that when the wheel was mounted the heat soaked into the components and would radiate into the wheel rim and raise the internal tire temperature and pressure.
Towards the end of 2015 and at the beginning of this campaign, its initial design was refined, with a carbon casing that is turned inside out used to control the heat within the brake drum and maintain it when the wheel is mounted.
Having noted an expansion of these tactics by several teams, Pirelli invoked its right to increase the starting pressures that the teams must meet on the grid, which has sparked some outspoken remarks from drivers as they know only too well how much this has an impact on performance.
In light of a belief that teams could be lowering pressures, Pirelli steadily increased the pressures as a safeguard, which will have hurt any team not able to perfectly manage the situation.
But one incentive for the fresh checking procedures is that if Pirelli is satisfied teams can no longer lower the limits, it may bring down the mandatory level.
Old dogs, no new tricks
Formula 1 is seen as cutting edge but much of what we see are often ideas from the past, reinterpreted to suit the current regulations.
As such, just over 10 years ago, something similar was going on, when a plethora of teams started to employ a tactic first used by Toyota in Montreal (2005), to help with its tire warming issues in the opening laps.
This was at the height of the battle between Michelin and Bridgestone and of course any advantage was deemed a risk worth taking, even if it did skirt very closely with the regulations.
Toyota's solution added to the blankets already in use, radiating heat into the wheel rim (illustrated above). This and other solutions used were subsequently banned as the FIA took affirmative action.
Has anything changed since Austria?
As the teams arrived in Austria, the new technical directive (TD/034-16) that changed when the tire pressures are measured arrived at a point that gave them little chance to change their procedures.
Even so, it wasn't expected that the teams already using these heating tricks would continue to do so in Austria, given that it could raise the pressures above the minimum set out by Pirelli.
That wasn't the case though, with the brake drum heaters clearly mounted on the Mercedes yet again. At the British Grand Prix, the heaters were seen in the garage too.
So perhaps the Mercedes trick was not about tire pressures, but more about ensuring a car that struggles with tire warm-up is not hampered by this at the start.
It could also be due to the way in which the brake drum is now designed, and needs to be heat soaked in order that the brakes work optimally at the start of the race.
While certain teams clearly enjoyed better performance from their previous use of these wheel rim heating tactics, an established order is difficult to upset and the more technically adept teams still rise to the top.
However, what we did see was a genuine improvement in a couple of teams who had not made use of these wheel rim heating tricks.
For example, could McLaren (which has pushed hard for clarifications about tire pressure monitoring) have been helped by the recent test change, or is its growing competitiveness a result of simple engine and chassis improvements?
But any belief beforehand that Mercedes' dominance would be wiped away by the change in procedures has been shown to be wrong judging by its great dominance the last two races.
More to come
Pirelli is eager to stamp out any similar development avenues and is now working with the FIA to change procedures for controlling tire blanket temperatures too.
Teams are currently allowed to have the tire in an initial three-hour heat cycle at 80C, followed by a one hour "boost" at 110C. Pirelli would rather the tire be heated at a static temperature, perhaps somewhere in the middle, say 90-95C.
The objective is that it's the same for every team and no real advantage can be gleaned over a competitor.
This will then further allow the tire manufacturer to lower the minimum starting pressures safe in the knowledge that they'll go up in a linear fashion when used, contrary to what has been seen since Monza last year.
Is this the end of the road for manipulation of tire pressures? Of course not. Teams will still look for ways to improve performance and use the way the rules are interpreted in order to do so, it just gets harder to find those marginal gains.
Co-author: Matt Somerfield, Assistant Technical Editor