After a mid-summer break, the Michelin Porsche Open Series resumes for races 12 and 13 at Thruxton over the weekend of 20/21 August. Two races for the wonderfully varied pack of Porsches will run alongside the weekend's international truck racing programme.It has been a mixed season for the driver who has consistently set the pace in the Porsche Open in recent times. In the 11 races to date, Richard Chamberlain's mighty 935 has consistently been the fastest car, but only five race wins have gone to the Cambridgeshire engineer. Several car dramas have hindered Chamberlain's campaign this year, but if everything is back in running order he will set a fierce pace around the high-speed Hampshire track, which has not hosted a round of the Open Series for many years.As ever, the biggest threat to Chamberlain will come from Rupert Lewin's 996GT2R, and a fine performance at Rockingham last time out took Lewin to a famous victory over Chamberlain. Lewin will now be battling to repeat that success on his car's first visit to Thruxton.Leading the chase of Chamberlain and Lewin will be Paul Howells (993 GT2), while the fastest of the class two cars will also be snapping at the heels of the class one pacesetters.Racing on his home track will be Tony Brown (964RSR) and his proven pace and experience at Thruxton could give the Poole-based racer his best results of the season. Brown's class rivals include Mark Allbutt (911GT3 Cup) and Martin Harvey in his 930 Turbo.Class three looks to be wide open, although the return to the grid of John Allen's 993 Supercup could make it the car to beat. Club Championship racers Mark Lillington (968CS) and Marcus Carniel (911SC) are other strong runners in class three, while the 944 pack in class four includes Charles Winterhalder and Andy Brown.