Romain Grosjean believes that unlocking the potential of the tires is key to Lotus recovering from a bad start to the Singapore Grand Prix weekend.
Teammate Kimi Raikkonen was the lead Lotus driver in Friday's first free practice session, 2.150 seconds off the pace, with Grosjean the best of the pair, 1.821sec down, in the second session.
Raikkonen has admitted that he expects a tough weekend, but Grosjean believes that struggles with the Pirelli tires are shrouding the potential of the car.
"The car is more or less the same as it was in Monaco and Budapest, where we were competitive, and there is no reason that the aerodynamic package suddenly doesn't work," said Grosjean. "It must be something on the tires.
"When you are two seconds off the pace, it cannot be that suddenly the car is going nowhere and everybody else has found two seconds in two weeks. Clearly, the performance is not what we wanted as we are far off on the time sheets. But we know what is wrong. It must be something on the tires. We will work on it and try to find some solutions."
Grosjean believes that getting the tires to work, both over a lap and over a race distance, will be particularly vital in Singapore. But while some teams have struggled with bringing in the front and the rear tires at the same time, Grosjean believes that Lotus has a bigger problem on its hands with making the tires produce the grip.
"tires will be the key, especially on a very low-grip city track," he said. "If you manage to make them work, the grip level is much higher.
"That [bringing in the front and the rear tires] is not the easiest part, but that's not the main problem. We have that a little bit, but that's not worth two seconds."