Shane Byrne resumed his status as the rider to beat so far during day two of World Superbike testing at Portimao, the Brit breaking the lap record in the process.

With the circuit finally reaching a state with which to set representative lap times, Byrne, who skipped the damp morning session, went straight back to the top of the timesheets with a best lap of 1min 43.294secs - just under a tenth quicker than Troy Bayliss' lap record and also on Pirelli race rubber.

Having been quickest during the post-season tests at the Algarve circuit two months ago before dominating throughout yesterday, these performances are quickly establishing Byrne as a serious threat for this year's title.

Things were fairly tight though, with fellow rookie Ben Spies proving less than two tenths slower than the Sterilgarda Ducati. It was a good session for the Yamaha Italia team, with Tom Sykes posting his most competitive showing so far in fourth position, just a tenth behind Spies.

The pair were split by the factory Ducati of Noriyuki Haga, but while he was quicker than team-mate Michel Fabrizio for the first time since joining Xerox, the team will be bemused at being comfortably out paced by BSB champion Byrne on a semi-private machine.

Hinting that this season's championship fight will be a competitive one between the main protagonists, Honda edged their way up the timesheets with Carlos Checa in fifth, while Suzuki maintained their continued presence towards the front of the field thanks to Max Neukirchner in sixth.

Having been well inside the top ten throughout the test, Jakub Smrz continued his impressive form with the seventh quickest time, just half a second off the leaders, and ahead of the factory Ducati of Fabrizio. The Czech rider did crash late on, however.

Honda pair Jonathan Rea and Leon Haslam were ninth and tenth to ensure that four of the five Brits competing in this year's championship are represented inside the top ten.

They were able to edge out Yukio Kagayama and the surprise morning pace setter Troy Corser on the BMW, although both riders will be pleased to be just over a second from the leading pace despite their positions.

Having debuted a new non-HANNspree livery yesterday, Ryuichi Kiyonari remains off the pace of his team-mates down in 14th, just ahead of Broc Parkes on the best of the Kawasaki contingent.

Shinya Nakano, meanwhile, got the better of Aprilia team-mate Max Biaggi, albeit down in 17th and 18th positions respectively, two seconds from the lead.

The fifth and final British rider on the grid, Tommy Hill, was 23rd fastest of the 27 riders.