Tyre suppliers Pirelli have declared themselves satisfied with the modifications made to their new F1 rubber over the winter - but how have things changed and how will the F1 teams cope with the difference?
The biggest factor in Pirelli's replacement of Bridgestone as F1's sole tyre supplier is in the strategy they have taken for tyre usage, which aims to make the rubber compounds less durable than the Bridgestones (which could last an entire race on some occasions) and ensure there is at least two pit stops in each race.
On top of this, however, there are a number of other important factors and considerations that will take some getting used to this season, both for drivers and teams.
FRONT TYRE GRIP
Pirelli have confirmed the design of the compounds used in the front tyres has changed since last November's Abu Dhabi test, and this will give the teams extra work to do to understand the outcome in the upcoming Valencia test in February.
When Pirelli was confirmed as the new supplier, the teams requested a stronger feel to the front tyre, meaning one that has a compound with the flexibility and softness to 'grab' the surface more, which leads to a more immediate response when a driver makes a steering input.
Pirelli did this, but during the test in Abu Dhabi it was noted by many teams that the balance between front and rear was not good, so that was improved by Pirelli between then and now.
Being comfortable with tyre performance is vital for a driver, and it is all about the feel of the tyre. Only in Valencia next week will the drivers finally learn whether they have an immediate liking, but if the Pirellis have indeed progressed this way then Michael Schumacher, Lewis Hamilton, Fernando Alonso and Felipe Massa are the four specific front-running drivers it is likely to please, while Jenson Button, who prefers a softer feel, may be less delighted.
Pirelli underwent a significant two-day test last week in controlled wet conditions (created by water-spraying lorries) in the Middle East, running under lights at night to keep to cooler temperatures.
It proved to be an important test, as some wet compounds that worked in the colder conditions in Europe were deemed not good enough in the warmer conditions in Bahrain - and with many of the early season races often having rain showers in warmer conditions (such as Malaysia and Australia) that is an important discovery.
The problem is, unless the teams can agree to do a similar controlled test themselves on wet tyres before the start of the season, they will not get to know how the tyres react until they are in a competitive situation.
Strategy is an important part of race planning, with specific computer models used to predict races even when it is wet. Without knowledge of how the wet tyres will perform and degrade over time, it will not be possible to create these models - so whenever the first wet races take place they could be even more of a lottery than normal.
Pirelli has been very open about their approach to this season - admitting that their first year will be very much exploratory. That could mean that there will be occasions when the tyres reach their limits unexpectedly or do not perform quite as required.
In the worst case, this could create a situation similar to the one experienced by Michelin in Indianapolis in 2005, when several of their tyres failed and, unable to determine a reason why, they were forced to pull out of the event.
To avoid such a situation, Pirelli is considering asking to run in some Friday practice sessions at grands prix if they have any concerns that changes may be required to ensure continued safety and/or performance of their tyres during the season. They will also conduct their own private testing programme throughout the year, although that will be more focused on developing for 2012.
For all this testing, however, they now need to get hold of a 2011 car to give accurate feedback, and that could cause problems.
They have been using a 2009-spec Toyota so far, and although they could develop this towards a 2011-spec model this is very expensive and, in an era where F1 is trying to cut costs, it makes no sense to do.
There are several approaches that could be taken for Pirelli to get their hands on 2011 machinery, but each comes with its own issues.
One solution is to allow all teams extra testing time at the circuits (to minimise extra transport and logistics costs) so they can make and test extra tyre developments. The problem with this, however, is that every F1 part is lifed - given a maximum mileage before it must be replaced - and simply running any lap has a cost to it, so the smaller teams that have budgeted for limited testing are unlikely to have the capacity to cope with this. Not to mention fitting it in amongst the already busy off-track schedules of the teams and the often well-filled support card of races.
An alternative but similar option would be to select only the leading cars to do extra Pirelli testing as they could afford it. This could be done away from tracks on the F1 calendar, but while the FIA could try to prevent teams from using these sessions to test new parts there are still ways around this and ultimately it would result in bigger teams benefiting from extra in-season testing.
A similar idea apparently on the table is to use the top seven teams to run single independent tests (so one test per team) but again that gives the teams selected the real advantage of experiencing an extra tyre test to those teams who are not selected.
Even further down the scale, another option understood to be on the table is to use a specific team's car to do all the testing - but that is completely unfair, whether it is a team from the front or the back of the grid. It has been proven in the past by Ferrari's close working relationship with Bridgestone during the last tyre war era that tyres developed specifically on a particular car layout can give significant advantage as part of that combination and have less effective overall characteristics when put on other machinery.
Finally, getting a true understanding of the new tyres before the start of the season is going to be very challenging for some teams, as there are many variables involved in testing.
Most teams ran the November test with their race drivers, and will do the same in February, but by that time not only will Pirelli's products have changed, but they are also likely to have their new car in action too, so too many variables will have changed to get a clear picture.
In contrast, this is where McLaren could be at an advantage. They used their test driver Gary Paffett to run on Pirellis in November, straight after he had driven on Bridgestones in the same car. That gave them the information they needed to create a model for their simulator which then allowed them to perfect their new car based on the general feel and characteristics of this year's tyres, as per their November spec.
They will then be using the old car to get another comparison on the new version of the Pirelli tyres in early February, which can then potentially go to refine that model and the new car before it hits the track at the subsequent test later in February.
So while the change in tyre manufacturer may seem simple on the surface, the complexities it comes with could well leave some teams scratching their heads for more than a while to come.