Kyle Busch rued a disastrous practice session at Iowa Speedway that saw him switch to a backup car. He explained how the rear grip didn't hold as expected, causing him to get loose and find the walls.On Saturday, August 2, Busch had posted the second-fastest lap time in his group and was poised to end the day strong, before he lost control of his rear and veered into the outside walls. He slammed nose-first and spun out from the impact, leading to severe damage that necessitated a backup car.The 40-year-old driver later spoke to the media and addressed the setback."Just trying to find the right rear limit, find the right rear grip that we needed and made some good changes to the car each time we came down," he said via X/Frontstretch."Felt really good in three and four there, I throttled up, car stuck well and I'm like, 'okay, the right rear is good, let's go', and drove it off into one with a little bit more trust factor in it. And obviously it wasn't there so got a little bit loose and overcorrected and just smacked the fence," he added.Kyle Busch revealed that he was unaffected by the crash and was fit to continue. He'll start from the rear on Sunday's Iowa Corn 350, making it his worst start this season. Meanwhile, his Richard Childress Racing teammate Austin Dillon showed enough pace to qualify inside the top-20.Kyle Busch sounded concerned about a 'treacherous' Iowa SpeedwayDuring a pre-race media session at Iowa Speedway, Kyle Busch opened up about his tire test at the track earlier in the year. He described how easy it was to lose control if a driver ever strayed from a racing line, a statement oddly reflective of his practice crash.“We went to Iowa Speedway for the tire test earlier this year, and we found out just how treacherous it is when there were only four of us there. You get out of the groove, and your car just wants to take off to the wall. So, it was very, very sketchy. I’m not even sure which tire Goodyear ended up deciding to bring back to Iowa,” he said via Sportsrush.comChase Briscoe, polesitter for Sunday's race, echoed Busch's concerns in a recent interview at Iowa. The Indiana native was among the four drivers who participated in the tire test.Kyle Busch has won an ARCA Menards and a Truck Series race at Iowa Speedway, but his Cup Series outing last year was met with an early exit due to mechanical issues.The RCR driver is 81 points behind the playoff cutline and will miss out on the postseason if he can't overcome RFK Racing's Ryan Preece, who also starts among the backmarkers at 33rd.