The decision by teams on whether or not to race with KERS (Kinetic Energy Recovery Systems) next year is so finely poised that it could be swung by how the new slick tyres behave, autosport.com has learned.
Teams are ramping up their efforts on KERS now that the season has finished, with more track testing of the devices due to take place from the first winter test at Barcelona later this month.
But even though the systems should bring a benefit of up to three tenths of a second per lap, the weight disadvantage of fitting KERS is now making it debatable about the real advantage.
The matter is further complicated by the fact that the predicted characteristics of the 2009 slick tyres could mean teams have to have as much of their weight distribution at the front of the car as possible. If that is the case, then there will be a considerable disadvantage from fitting a heavy KERS, which could weigh as much as 60kg, at the rear of the car.
Teams are currently evaluating their options for KERS, with a number of outfits admitting the picture should become much clearer after the first winter testing of slicks.
When asked by autosport.com about how close the call is between racing KERS or not, Honda Racing team principal Ross Brawn said: "It is a close call and a lot of depends on what we find with the tyres when we start to spend more time with them.
"We have all predicted what sort of weight distributions we want and that incorporates KERS in our car. But of course, if the weight distribution has to change, then it is much more difficult to move the major elements of KERS around the car. It depends how well we have predicted what the weight distribution should be.
"If you start making compromises on the weight distribution you may find you lose the potential advantage of KERS. It is roughly speaking 0.25 seconds or 0.3 seconds per lap, and that is very easy to lose if the car is not working properly."
Williams technical director Sam Michael said that his team were keeping an open mind about what to do prior to the first proper slick tests.
"It depends on what the slope is of optimum weight distribution versus laptime," Michael told autosport.com. "You can design your car with any weight distribution, as you just move your wheelbase, or you can change your suspension geometry to get the weight distribution you want with no ballast. It depends to what extent the teams want to go to achieve that.
"Looking at the tyres, there is more front grip available than rear because they have filled the grooves in, so the balance is going to tell you that you need to move the weight forward as there is more front grip available.
"But it is a slick tyre. It works differently to a grooved tyre, and will work differently in different temperatures, so no one knows 100 percent until you get to running it. And it will continually move. There is no such thing as an optimum weight distribution, it can change from one track to another and change very significantly with track temperature
"In terms of KERS, the first challenge is to make it safe and reliable, and the second thing is performance. Once we have those two things together that is when we will take it to a race."
The tendency for the front slick tyres to provide more grip than the rears came after teams vetoed a request from Bridgestone to reduce the size of the front tyres - because of the impact that would have on car aerodynamics and suspension settings.
Bridgestone's director of motorsport tyre development Hirohide Hamashima said: "We proposed to reduce the front tyre size, but the teams refused.
"We therefore changed the rear tyre construction to increase grip, but we cannot find a compromise at the moment. If teams design the car similar to this year then they will struggle with oversteer tendency, so teams which have an understeer tendency to their car will be good in the beginning.
"But the teams will struggle to design the car because with KERS the rear section will be heavier."
Despite the debate over the ultimate benefit to a laptime by running KERS, Brawn thinks there are some tracks where there will be much to gain from racing with one.
"It can be quite a strategic advantage," he said. "There are a number of tracks when the gain at the start could be two or three car lengths between a car with KERS and a car without KERS.
"Some tracks will provide no benefit because they don't have long enough straights before the first corner, but there are a number of tracks where KERS will be very relevant for the start, and could mean two or three car places."