Bill Auberlen vaulted to the head of the timesheets just as the chequered flag on the second of two practice sessions for the Grand-Am Rolex Series in Mexico City, giving the #05 Luggage Express Sigalsport a place in the sun for at least a few hours.

Although the team was on form at the season-opener at Daytona last month, Auberlen's lap at 1min 22.458secs at the Autodromo Hermanos Rodriguez surprised many preparing for Saturday's Mexico City 400k. The lap was quicker than the existing Rolex Series track record of 1min 22.732secs - established by current points leader Scott Pruett in qualifying last year - and came after Auberlen, who is sharing the #05 Riley-BMW with Matthew Alhadeff, had hovered just outside the top five throughout the later stages of the session.

The sportscar veteran's last-lap flyer knocked Oswaldo Negri's #60 Michael Shank Racing Riley-Lexus off top spot, despite the session being Auberlen's first at the Mexico City track in a Daytona Prototype. The two-time Rolex Series GT champion drove in the 'junior' class in both previous Rolex Series events at the Autodromo Hermanos Rodriguez, and his experience clearly translated to the quirky DP machine.

"We pulled that off with just seconds to spare," Auberlen confirmed, "We were panicking a little, but the car was there all the time. We were always around the top but, in the first practice session, we had a little gearbox melee. We got the problem resolved, but it cost us a little time in the second session.

"We then evaluated some sway bar settings, tried a new spring and just threw darts at the board. Matt drove first and I took over and we put on some new tyres. I put together two flyers at the end, got baulked on the first one, but the second one got it done. This just shows that this team has the pieces. They give me a lot of freedom to spend their money and let me go out and just buy what we need. I don't think [team owner] Gene [Sigal] likes it so much, but it shows the commitment!"

Negri had himself leapt to the top of the time charts in the final five minutes of the session, claiming P1 with less than two minutes remaining. The Brazilian also led the opening day of practice in Mexico City last year, before a crash in practice prior to qualifying left him and co-driver Mark Patterson behind the eight ball for the remainder of the weekend.

"We are not quite where we want to be yet, but this was a good start for us," Negri said, "The biggest thing is that Mark did a great job today. He was really quick here last year, but today he was even faster even when he was running with tyres that had a lot of laps on them, so that's very encouraging for the race. Michael Shank Racing has once again prepared a great car and the Lexus guys have been fantastic, so there's no question I'm optimistic about this weekend."

Third quickest on the day was Jan Magnussen in the #10 SunTrust Riley-Pontiac. Both the Dane and co-driver Max Angelelli were quick in the day's two practice sessions, with Angelelli turning in the fastest time during the opening outing.

"I'm happy with the way today went," Magnussen said, "I got a lot of laps and time in the car, and did most of that last session. We still have some work to do, but it's a really good place to start.

"It looks like we've got a good set-up for qualifying so, now, we have to tune the car so it will be as ideal as possible for the race. I'm sure we will get that done tomorrow and Saturday morning. The track was a little slippery at the start today, but we're good to go with the weather, which means the track will get better and better as we go along."

Marc Goossens, who drove a NASCAR Busch Series car at Autodromo Hermanos Rodriguez last year, was fourth-quickest in the #91 Riley-Matthews Motorsports Riley-Pontiac, while defending Mexico City 400k winner Pruett completed the top five in the crowd-pleasing #01 Telmex Chip Ganassi Racing Riley-Lexus. The Grand-Am veteran is joined for the first time this weekend by new Mexican co-driver Memo Rojas.

The top ten DPs in the final practice session were covered by less than one second.

The GT class was not quite as frenetic as its bigger brother as Spencer Pumpelly turned the best lap of 1min 29.966secs to claim the top spot with slightly more than ten minutes remaining. The #67 TRG Porsche was the only GT entry to top the 100mph barrier in either of Thursday's practice sessions, as Pumpelly shared track time with 18-year-old co-driver Scott Schroeder, who makes his Rolex Series debut this weekend. Schroeder, who competed in the season-opening Grand-Am Koni Challenge Series event at Daytona, turned testing laps within one second of his considerably more experienced co-driver.

"The track gets better and better each session, and the times will keep dropping," Pumpelly reported, "The track is bumpy in parts and the Porsche handles it pretty well, but the Mazdas and the [Pontiac] GXPs will be good too. I don't have a lot of laps here, but the TRG guys put together a really great effort and I love the fast track. Our biggest plus is the winning experience TRG has here."

Second quickest in GT was Andrew Davis in the #72 Tafel Racing Porsche GT3 he shares with Nathan Swartzbaugh.

"The track is super dirty like last year, but that will get better," Davis said, "We made some changes in pit-lane and they worked out. The Tafel Racing team does a real good job and our Porsche is fast. I wouldn't say Porsche is the car to beat, as the other cars and guys are going to be quick, but I am proud of the team. We tried a lot in two sessions and it showed at the end."

The best of the Pontiacs claimed third spot in the hands of Kelly Collins, who lapped the #07 Banner Engineering GXP.R in 1min 30.563secs. The reigning Mexico City GT class 'champion' shares the #07 machine with Paul Edwards, who is seeking a hat-trick of victories at the circuit this weekend.

SpeedSource Mazda owner/driver Sylvain Tremblay was fourth quickest in the #70 RX-8, while Wolf Henzler rounded out the top five in the #74 Tafel Porsche.