Marlboro Yamaha men on second row at slippery Rio.

Marlboro Yamaha Team riders Carlos Checa and Max Biaggi quickly got to grips with the slippery Jacarepagua circuit this afternoon, clocking sixth and eighth quickest times in the opening qualifying session for the season-ending Rio GP.

The Brazilian circuit is one of the more slippery and bumpy tracks on the GP calendar and Checa was one of several men to slide off during the session.

"Both our guys have been trying to find the track's grip level, and I guess Carlos found it!" smiled Marlboro Yamaha Team manager Geoff Crust. "He went down when he flicked into a corner and lost the front, but after that he was pretty happy with his other machine. I think people forget how bumpy this track is, and it's definitely quite slippery too, though it should get better as more rubber gets laid down. Max has been working towards a set-up that doesn't upset the bike so much, he's been looking for stability on the bumps."

Carlos Checa slid off in the early stages of today's session but bounced back on his other bike, battling for a place on the provisional front row and eventually ending up sixth, just 0.627 seconds off pole. "We tried a front tyre with a different casing and it didn't work the way we wanted it to," said the Marlboro Yamaha Team man. "I flicked into a turn and lost the front as I hit maximum lean. I think some of the problem comes from the rear, because we've now got so much rear grip, and this is something we're working on with Michelin.

"So far the lap times aren't as fast as last year's but I think that's just grip; this track doesn't get used much, so the asphalt is a bit dirty. I'm happy enough though, the bike seems quite good and I don't think we'll need to make any changes to geometry, pivot points and so on, we can just focus on normal changes, getting the suspension balance and engine settings right for the race."

Max Biaggi was eighth fastest at Rio today, preferring a more tentative approach to the first day of qualifying. The Marlboro Yamaha Team man, who has scored more pole positions than anyone else so far this season, expects the pace to increase tomorrow as the circuit's grip level increases. "This track seems very slippery and more bumpy than last year, so it's important to find the right setting before going for a very fast lap," said the Italian.

"We want the bike to work smoothly around here and that's what we've been focusing on throughout both of today's sessions. Tomorrow will be much more important though, because the surface will be more grippy, and that means we can ride harder and also do more effective work on race settings, because the conditions will be closer to what we'll have to contend with in Saturday's race."

Newly crowned World Champion Valentino Rossi (Honda) left it to his last lap to leapfrog to the top of the times, bettering Kenny Roberts (Suzuki) by just 0.044 seconds. The 22-year-old, who wrapped up the title at last month's Australian GP, is determined to win his 11th victory of the year here. "I'll be giving 100 per cent to win onb Saturday," said Rossi, who won his first dry-weather 500 success here last year. "This is not the easiest track to get a set-up, we've still got a lot of work to do to find settings that will work over race distance."

Outgoing World Champion Kenny Roberts was back up front in today's opening qualifier, posting second-fastest time behind his successor Valentino Rossi. The American hasn't qualified on the front row since June's Italian GP. "This may be the last race of the year but I'm still trying as hard as ever," he said. "For tomorrow we need to improve the gearbox and the way the bike comes off the corners."