The Bend Motorsport Park. THOMAS SARGENT has gained a key advantage in a potentially championship-changing day in the Porsche Michelin Sprint Challenge Australia Series at The Bend Motorsport Park.

Both Pro and Morris Pro-Am championship pictures were dramatically altered today as key contenders in each series struck dramas at the South Australian circuit.

Tegra Australia driver Sargent's championship lead was on a knife's edge following the opening sprint race of the weekend after finishing second to nearest rival Ryan Wood - taking their streak of 1-2 finishes to eight, with four wins each.

The pair were then battling furiously throughout the early stages of the 22-lap Jim Richards Endurance Trophy race, Sargent fending off attack after attack from the team Porsche New Zealand / Earl Bamber Motorsport entry.

However, Wood's car dramatically slowed following a mid-race Safety Car, fuel pressure issues ultimately forcing the young Kiwi out of the race.

In such a tight season, it was a critical moment in the pair's ongoing title battle as the series enters the second half of the year.

Wood had led Sargent in race one after a furious early battle saw the Kiwi pass the early leader.

The pair finished 1-2 again with Lachlan Bloxsom third, while Brett Boulton took Morris Pro-Am over Andrew Goldie and David Grieg.

In the Enduro Cup race Sargent again grabbed the early lead after starting second, before holding on in a furious battle throughout the first eleven laps.

The mid-race Safety Car, for Courtney Prince's stranded Local Legends entry at Turn one, slowed things up before Wood's issues became apparent on the restart.

His slow restart bottled the field up with Bloxsom swamped by his closest contenders after being unable to overtake before the control line.

He dropped back to fifth before recovering to third after a tense final lap battle from Tom McLennan.

Madeline Stewart was fifth while Jason Miller had held third until the closing stages before dropping back to sixth.

It was a dramatic day for class leaders at The Bend after both Morris Pro-Am and Class B contenders struck issues at various points.

Pro-Am points leader Sam Shahin was a non-finisher in race one of the weekend after a sizable turn six incident, handing the championship lead to nearest rival Brett Boulton.

In Class B, Brad Carr won the opening race before he spun off in the Enduro Cup affair, handing the top spot to Lachlan Harburg.

Shahin then charged through to grab the Pro-Am lead in race two before he again struck issues, Boulton in the best possible position to capitalise and grab the Morris Pro-Am win over Goldie, Pan Boyaci and Shahin in fourth.

Harburg claimed Class B after Carr's issue, Nathan Sticklen next.

One race completes the round on Sunday afternoon, set to start at 11:10am local time with live streaming on 7plus.

Thomas Sargent, Pro:

“Very chuffed with that one, its always good racing the long (endurance) one, unfortunately it got shortened by the safety car. Its unfortunate to see those things happen with Ryan, but it’s important for us to capitalise on those races when you can get them so, it was just our day today so very, very lucky. I’m looking forward to tomorrow and some more hard racing , couple more changes on the car and will be good for the race.”

Brett Boulton, Morris Pro-Am:

“It was an awesome race, I’m pooped after that one, but it was great fun. After the restart Sam (Shahin) caught us pretty quickly, he’s very fast here and an awesome driver, so I was just trying to hang onto the back of him and be as quick as I could off the restart. Sam made an error and I went through and it was just a case of trying to manage the race from there.”

Lachlan Harburg, Class B:

“I would like to say it was down to skill but it was more luck, unfortunately Brad (Carr) had a spin, so I’m not getting ahead of myself, but its really good to come away with the win. It was just nice to keep clean with a lot of guys making mistakes out there. It’s just a mega track as it’s really designed for these cars, it really rewards bravery through the fast stuff. I’m trying to get my head around it but just loving this car here, its been awesome.”