UPDATE 1-Motor racing-Haas shows class, then farce in Australia

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MELBOURNE, March 25 (Reuters) - A weekend that began with back-slapping and high-fives for Haas after their best ever Formula One qualifying finished with ‘heartbreak’ and fines after both the team’s cars retired before the halfway mark of the Australian Grand Prix.

Danish driver Kevin Magnussen started Sunday’s race at Albert Park in fifth place with French team mate Romain Grosjean lining up in sixth after Red Bull’s Daniel Ricciardo took a three place drop.

They were running fourth and fifth prior to their first pitstops where it all went wrong.

There was obvious alarm from the mechanics as the cars were released, and they each rolled to a halt before completing another lap.

The team revealed later that it had committed the same mistake twice, failing to properly fasten wheels on each car after changing their tyres.

“It was just a bad pit stop,” said team principal Guenther Steiner.

“The wheelnut was on but it was cross-threaded. That doesn’t tighten the wheel up but for the mechanic, it feels like it is tightened and it wasn’t.”

The stewards imposed fines of 5,000 euros ($6000 approx) for each incident, adding another sting to the drivers’ huge disappointment at the season-opening race won by Ferrari’s Sebastian Vettel.

“It’s a very tough one to swallow for the whole team,” said Magnussen.

“To have both cars not finishing – having been in such good positions and with so much anticipation – it’s just heartbreaking to finish like that.”

Steiner said it was “almost unbelievable” for both cars to suffer the same fate in one race but put the blame down to a lack of pitstop practice and shortage of spare tyres.

“This weekend was very intense for us, we had issues in FP1 and FP2,” said Steiner of Friday’s free practice sessions.

“When we get to Bahrain (we need) to start as quickly as possible to practice there.

“A lot of people who are part of the pit crew are leaving early to set up out there so you never have a full crew. If you train with a half crew, it can be even worse.” (Editing by Pritha Sarkar)