How Suspension Design Won Denny Hamlin a NASCAR Race in the Pits

It looked like Denny Hamlin was set for a third place finish with two laps remaining in the Toyota Owners 400 NASCAR race at Richmond until a spinning car drew a caution flag and sent the race into overtime. Hamlin pitted for fresh tires and his crew was able to put him out front and leapfrog the frontrunners by over a second for that final restart. It all came down to a single tire on a single corner of the car.

Pit stops in the NASCAR Cup Series have become incredibly fast as they transitioned to single-lug wheels. It’s not unusual to see four tire changes in the single digit seconds now. The No. 11 Joe Gibbs Racing pit crew that works with Denny Hamlin has emerged as the dominant pit crew this season and all but one of their pit stops last night was down in those single digits. The unspoken variable here is that each race track commands a different suspension setup from the cars. That means tires come off and go on the car differently from week to week.

An optimal suspension configuration for Richmond Raceway will often lead to a left rear corner without a lot of droop. This means that when the car is jacked up in the air, the wheel will not drop very far down because everything is configured so tightly. This can result in the tire being very close to the lip of the fender and means that tire changers and carriers have to be very precise on the exchange.

The left rear tire is what ultimately appears to have made the difference on that final pit stop which saw Denny Hamlin and Martin Truex Jr. swap position on pit lane with Hamlin taking the lead for that final restart. Hamlin’s crew was able to execute another successful pit stop, which showed that they changed four tires in 8.99 seconds while the No. 19 crew for Martin Truex Jr. was over a second behind with a time of 10.29 seconds for their four tire change.

Let's watch that pit stop.

We can see the No. 19 pit crew moving quickly on the right side of the car in the video above. As they make their way to the left side, we can see a delay on the left rear. This is where that limited droop comes into play and makes that left rear tire harder to pull. That delay quickly compounds itself -- the jack handler is late installing that tire, which results in the front tire changer turning to lower the jack instead of the jack handler, which deviates from the crew's standard pit stop process.

The overall delay is almost hard to catch in the video because it seems pretty insignificant. The car leaves fairly quickly, but the margins in the NASCAR Cup Series are so small now that every tenth matters. The pit crew of the No. 23 of Bubba Wallace showed one of the worst-case scenarios of this situation. They had similar delays on the left rear, but the issues compounded even worse as the front changer dropped the jack before the rear changer was done fastening that rear tire. They had to jack it back up to finish tightening it which resulted in a pit stop of almost 13 seconds.