Several Toyota drivers arrived at Iowa Speedway with the same unsettling problem of inconsistent brake performance, which made the fastest short track on the NASCAR Cup Series schedule especially difficult to handle.

Denny Hamlin, Chase Briscoe, Riley Herbst and Bubba Wallace all encountered brake concerns during the weekend, with Hamlin eventually explaining that the problem came from the combination of their brake choice, car setup and the extreme demands Iowa placed on the components.

Hamlin’s No. 11 Joe Gibbs Racing Toyota suffered the issue almost immediately in the race. After his team changed the brake-cooling ducts before the start, NASCAR sent him to the rear, and by Lap 3 Hamlin reported that his brakes were gone.

The problem left him managing the car instead of chasing the win, yet he still brought it home P5.

Denny Hamlin explains how at times he almost had to drive with no brakes

The biggest difficulty was that Hamlin could never rely on a consistent amount of braking force when he reached the corners. On Actions Detrimental he explained that the brake pads could be knocked back on the straightaways, while their response also depended heavily on how much heat had built up.

“Well, because of what I had to do in the car to make it first not wreck on corner entry … I don’t know whether the brake pads are going to grab the rotors or not,” Hamlin said. “It just depends on how much they get knocked back on the straightaway, and it depends on how hot they are at the time.”

Hamlin estimated that he had around 10% braking capability for roughly 20% of the time, about 50% braking for 60% of the race and full braking for only around 20%. The strongest pedal came following cautions, when the components had a chance to cool, but that advantage lasted only about three laps.

“I’d have decent brakes to where the pedal was good, but the minute it got any sort of heat to it, they went away,” Hamlin explained. “And when they went away, they went away right off the bat. So, it just didn’t slowly work its way down. The pedal then would just go all the way to the floor.”

That forced him into a constant battle on every straightaway. Hamlin pumped the pedal to rebuild pressure before the next corner, though the effect varied with temperature.

“So, then I’m chasing the car. Hopefully, nobody’s around me,” he said. “Every straightaway I’m trying to pump these things up.”

The same issue had already appeared during Saturday practice, when Hamlin stopped running because he could not continue safely. Briscoe experienced a similar failure during the race, while Herbst and Wallace also dealt with brake concerns.

Why Iowa exposed the problem

Hamlin believes the issue was due to a brake combination that the JGR and 23XI teams had selected in search of additional performance. He acknowledged that the choice had been used successfully at other tracks, but Iowa exposed a weakness that had not appeared elsewhere.

“We tried to run something a little bit different, not unknown,” Hamlin said. “Other teams have run it quite a bit before. I wanted to lean on 23XI. They had been pretty strong at this track over the last year or so.”

The technical alliance had provided the teams with information, but individual crews still made their own decisions about setup and brake combinations.

Hamlin ultimately believed his team may also have received a bad batch of pads because other cars using the same components had previously operated without comparable problems.

Meanwhile, Iowa’s layout magnified the issue. The track combines high speeds with short straightaways, giving the brakes little time to shed heat before they are called upon again.

Hamlin stated, “With it being the fastest short track on the planet, it doesn’t have long straightaways to cool, but it has fast speeds that are trying to clamp down on that rotor. So it creates heat really, really quickly.”

That scene turned a brake choice that had worked elsewhere into a major concern at Iowa, with several Toyota teams spending extensive time making adjustments before and during the race.

The rule that left Denny Hamlin with few options

The situation also created a dispute over NASCAR’s brake-pad regulations. Teams cannot simply replace their brake pads during the weekend unless the manufacturer identifies a defective product and notifies NASCAR.

They can bleed the brakes and replace cracked rotors, but a pad change would have required Hamlin to wait until after the race began and lose substantial track position.

Hamlin said he asked NASCAR what would happen if his team changed the pads anyway because he viewed the situation as a safety issue.

“I told them I’d start on pit lane,” Hamlin said. “We have a major problem.”

He understood the reasoning behind the regulation, since NASCAR does not want teams to run one type of pad in qualifying and switch to another for the race. However, he argued that the rules need an exception for genuine safety concerns.

“And that’s their argument, right,” Hamlin said. “We do not want 36 teams having a qualifying brake pad and a race brake pad.”

His preferred solution involved a substantial penalty that still allowed a team to address a dangerous mechanical problem before the green flag.

A fifth-place finish from a race he thought was lost

The severity of the problem changed Hamlin’s expectations before the race. After qualifying 29th and then being sent to the rear because of the cooling-duct change, he entered the Iowa Corn 350 expecting simply to survive.

His crew continued adapting the car so he could control it with limited braking performance. That work allowed Hamlin to complete the 350-lap race and finish fifth, while Briscoe followed in sixth. Ty Gibbs won, with Christopher Bell, Ryan Blaney and Josh Berry completing the top five.

The P5-place finish also preserved Hamlin’s position at the top of the regular-season standings, leaving him 103 points ahead of Gibbs with three races remaining.