Overnight rain and lower than expected temperatures in Montreal on Saturday morning have left teams facing a nightmare dilemma over tire strategies for the Canadian Grand Prix - that could blow open the battle for pole position.
A number of drivers complained about bad graining on the super soft tires in free practice on Friday, and Bridgestone chiefs think the tire choices for qualifying will not be straightforward.
Overnight showers have washed away any rubber laid down on Friday, and the track temperature is no warmer than yesterday. Bridgestone's director of motorsport tire development Hirohide Hamashima says current predictions are that a standard one-stop will be impossible.
Furthermore, he also thinks that with the front-running teams likely to opt to qualify on the medium tire, there is a chance slower outfits may gamble on taking the supersoft option in Q3 -- to get themselves at the front of the grid. That could result in a surprise car being on pole position.
"FP3 will be very, very important to compare between the option and the prime to see if the option is quick," said Hamashima. "If that is the case then maybe the grid will be interesting. Someone could take a risk with the option tires for qualifying, and in that case we could have a little bit of a different story from the past races."
The graining experienced on Friday was caused by the tires actually tearing, rather than excessive temperature, and Hamashima thinks the situation is on a knife-edge for teams.
"It is not normal graining because it seems the rubber is tearing, so not melting," said Hamashima. "The graining itself is a bit different, because the surface itself is very, very smooth - and smoother than two years ago. So the tire isn't gripping, it isn't getting the proper temperature and there is no deformation - which is why the rubber tears off."
Hamashima thinks that the title-fighting teams may be forced to choose tires that are better for the race than qualifying - with the top ten drivers having to start the race on the tires they set their best qualifying lap on.
"I reckon it will be a minimum of two stops according to the current data," said Hamashima. "Maybe the top teams will use the supersoft in Q1 and then for Q2 and Q3, maybe they will use prime.
"With the current situation -- the lap time difference between the prime and option tire is very small. The super soft has better traction, however, it is poor with lateral support so the lap time itself is not so better. Also when the car is heavy, the option tire is slower than the prime tire - about six-tenths of a second."
Hamashima estimates that the current degradation prediction suggests that the medium will lose seven seconds per half race distance, with the option a whopping 16.2sec per half race distance.
"Maybe the teams will start with the prime, then next stop prime, and then a very short stint with super soft. That looks like the best way."
When asked if anyone could risk trying a one-stop strategy, Hamashima said: "It's currently impossible. Even for very slow people, it's very, very difficult.
"In 2008, we saw the track improvement over the weekend was quite dramatic -- and in that case they could use the super soft. But the current temperature is not so high, so it will be very, very difficult."