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After qualifying a season-high fourth on Saturday, Mardenborough was running third and on course for at least a first podium finish in two years when the #24 Nissan GT-R he shares with Mitsunori Takaboshi got stuck in second gear.
Takaboshi had briefly led during his stint, passing Nirei Fukuzumi's polesitting ARTA Honda on the opening lap only for Fukuzumi to repass shortly after an early safety car period, before coming in on lap 25 of 66 to hand over to Mardenborough.
Faster pitstops from several other cars put the Kondo car back down to fifth, but Mardenborough regained two positions and was closing on the TOM'S Toyota of Ryo Hirakawa in the fight for second before the misfortune struck.
"Mitsunori did a great stint, and I was on a different tyre compared to Mitsunori, to make sure it lasted," Mardenborough recalled to Motorsport.com.
"The tyre felt consistent and when I passed [Naoki] Yamamoto [in the Kunimitsu Honda], I could keep the gap to the ARTA car [behind] constant, and I was catching the #37 [Hirakawa].
"It was going well until I couldn’t change gear anymore. We got stuck in second gear. I tried all the resets, manual shift, and nothing worked.
"When you’re doing 100km/h and everyone else is coming past you doing 300km/h, it’s pretty demotivating and disheartening."
Asked what result could have been possible, Mardenborough replied: "At least third. I could see I was catching Hirakawa, and I saw at the end they all finished close [in the fight for second].
"My pace at that point was getting better, I was in the mid-1m31s and still improving. And the [eventual] gap from second and third to the winner was only 10 seconds.
"Third [was on] for sure. A win? We would have been up there. It’s really soul-testing."
Mardenborough and Takaboshi finally finished five laps down in 14th after pitting to change the steering wheel, meaning the point they scored in the opening round of the season at Fuji for 10th place remains their only one of the year.
Kondo will get one more chance to capitalise on its lack of success handicap weight next time out at Suzuka, where Nissan's NISMO entry was victorious earlier this year.
However, Mardenborough admitted that the Japanese Grand Prix venue is the least well-suited of this year's circuits to the Yokohama tyre.
"We’ve gone well there in testing and I’m always optimistic," he said. "But it’s down to whether we can make the tyre last at a very high-load circuit.
"Our best chances were Motegi and Fuji. Everyone else is heavy [at Suzuka], which is good. But I would have picked Suzuka last [of the three tracks] for our best chance."
#24 Realize Corporation ADVAN GT-R
Photo by: Masahide Kamio
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