Noah Gragson fastest in Iowa practice, while five drivers have tire issues.

NEWTON, Iowa — Five drivers had tire issues and two will go to backup cars after Friday's 50-minute practice session for Cup cars at Iowa Speedway.

Christopher Bell and Austin Cindric each will go to backup cars for Sunday night's inaugural Cup race at this ⅞-mile track after they had a right front tire go down and hit the wall during practice.

MORE: Results from Cup practice

All the tire issues happened about 20 laps into a run.

"What is even more concerning and makes it way more confusing is the fact that we had three cars out here at a tire test that did 50-lap runs and none of us blew a tire," Bell said. "So, I don't know. But yes, It is very, very alarming and there are red flags all over the place that we had so many tire issues today."

Bell took part in a tire confirmation test on May 28 with Kyle Larson and Brad Keselowski. Speeds were faster Friday than what those three ran in the test.

Said Cindric of the tire issues: "We certainly weren't one of the only teams to have tire issues, but it definitely seems like there are some limitations. It was a good lesson to learn maybe before the race, but there's a lot of work for the team to get ready for qualifying (Saturday). It's unfortunate, but I'm glad we've got time to get one ready for qualifying."

Ty Gibbs and Tyler Reddick each had a right front tire go down. Ross Chastain had a left rear go flat. Each of those cars did not hit the wall.

Noah Gragson was the fastest in the practice session with a lap of 137.988 mph. He was followed by Gibbs (136,559 mph), Alex Bowman (136.334), Justin Haley (136.269) and Chase Elliott (135.811).

"With it being a new repave it definitely created some challenges and a guessing game coming into this race, but I felt good on the Ford Performance simulator and it felt really close to how we unloaded in real life," Gragson said. "We were just a little loose and got better throughout the practice. I started pretty loose in, but once we got that under control it felt like the car had a lot of speed and then came into the garage.

"Obviously, it does have a lot of pace, so I'm really excited to see what we can do with it here for qualifying. There's still a long way to go this weekend, but the car feels pretty good and everybody on this Bass Pro/Winchester team has been working hard. We've kind of been in a slump the last four or five weeks since Darlington, but we've got a really fast race car and continue to work well with each other and it's a good place for us to try and turn it around."

Qualifying is scheduled to begin at. 1 p.m. ET Saturday on USA Network.