Both Giancarlo Fisichella and Adrian Sutil grappled with low grip during the practice session after rain lashed the bumpy Interlagos track ahead of Sunday's Brazilian Grand Prix, the final race of the 2008 FIA Formula One World Championship.
Heavy rain before the morning session left the 4.309km track damp and cool and both drivers struggled to get heat into the harder tyre compound available in this event.
With temperatures remaining similar in the afternoon and showers lingering, the team adjusted the aero balance to compensate for the lack of grip.
Fisichella and Sutil duly improved their times by one second to set the 19th and 20th quickest times of the afternoon, just over a second from the fastest lap of the day.
Both completed two 90-minute practice sessions, working through the standard on Friday programme of tyre and set-up evaluation.
"We didn't have any problems today so we could get through our schedule as planned. I was quite happy with my performance and we can see how the tyres are working now," a satisfied Sutil later said.
"The soft ones seem to be better compared to the medium tyre at the moment. We'll study the data and work on it for tomorrow," added the German.