September 25, 2022

The composite body of the Next Gen car withstands impacts much better than the metal Gen-6 bodies. No more wall bumps with a high chance of a cut tire a few laps later.

Instead, a new word entered the NASCAR lexicon: rear toe link. A broken rear toe link can knock a rider out of the race as quickly as a cut tire. Let’s learn what the rear toe link is, what it does, and why making it sturdier would actually be worse for drivers and fans.

Toe

Look at a passenger car above your head. The four tires would be oriented parallel to a line drawn along the length of the car, as shown to the right.

Racing—especially racing on banked ovals—requires setting up the car to keep the tire in contact with the track as much as possible. Toe-in is one of the adjustments a team can make to help optimize tire contact patches.

The toe is the gap between a tire and the centerline of the car. The diagram below shows inside toe-in (positive toe-in), zero toe-in, and outside toe-in (negative toe-in). Remember that you are looking at the car from above in this graphic.

A graph showing the toe variations possible on a car

Toed out means that the front of the tires are further apart than the rear of the tires. Toed in means the opposite. Engineers specify toe either by an angle or a distance – usually the difference between the front and rear of the opposing tires.

Toe links

The rear toe link (shown below) brings one side of the wheel/tire closer to the centerline of the car or pushing it further away.

A graphic showing the rear toe link
Adapted from the NASCAR rulebook

The rear toe link, made by Visser Precision to NASCAR specifications, is a rod with a connector on each end. The side with the circular connector attaches to the rear upright and hub assembly (where the wheel and tire are mounted), while the fork-shaped piece connects to the upper control arm.

The graphic below shows the rear toe link (in white) as part of the rear suspension.

  • The upper and lower control arms attach to the frame.
  • The turquoise element is the shock absorber.
  • The mustard-colored rod is the rear anti-roll bar.
  • The burgundy part that’s barely visible is the weight jacker assembly – it’s the part that is adjusted when a crew member puts one of those long wrenches through a hole in the rear windshield.

A graphic from the NASCAR rulebook showing how the rear toe link attaches to the car.

NASCAR rule book

Teams adjust the wedges to change the effective length of the toe link. Even if you don’t want a toe, you still need the toe tie to secure the toe to zero.

Rear pinch link reinforcement

Given how strong the other rear suspension components are, it’s no surprise that the rear toe link is the component most likely to break when a car hits the wall.

It’s not an accident. The rear toe link is one of the easiest suspension parts to replace because it only has two connections. As Chase Elliott’s team showed in Charlotte, teams can even replace the rear toe link on pit road. It’s not a quick fix and it’s likely to cause the team to lose turns. But they are still in the running. I suspect it is also one of the less expensive parts of the suspension.

If a suspension part should break, the rear pinch link is the best part to break.

It’s safer for the driver if a part of the car breaks because it takes energy to break things. The energy used to break the car is energy that does not reach the driver.

A racing car traveling at 160 mph has about the same energy as that stored in one kilogram (2.2 pounds) of TNT. Because energy cannot be created or destroyed, all of that energy has to go somewhere when a car stops. Every crumpled fender, every crushed piece of foam and every squealing tire transforms energy. The energy dissipated by the car does not reach the driver. The rear pinch link is one in a chain of sacrificial components.

The Next Gen car is stiffer than the car it replaced. Much of this rigidity is due to the reinforcements that protect the driver from debris entering the cockpit. Greater stiffness dissipates less energy, which means more energy reaches the conductor.

“The little slaps against the fence that maybe don’t look so big,” Joey Logano said on SiriusXM NASCAR Radio’s “The Morning Drive,” “you feel them a lot more than before, it’s sure.”

This makes the role of intentional “weak links” like bumpers, foam and rear pinch links even more important. Safety features that protect drivers in potentially serious accidents sometimes make them feel the small impacts a little more.

Indestructible cars make racing worse

Leaving safety aside, there is a strategic rationale for not making the Next Gen car indestructible. If a pilot can hit a wall and just keep going, the importance of the skill diminishes. Races turn into bumper cars and drivers become more aggressive as they can do so without penalty. In the worst case, this leads to more accidents – and potentially more serious accidents.

The Next Gen car requires drivers to employ a different skill set. The line between “fast” and “in the wall” is thinner than ever. Drivers must combine finesse behind the wheel and aggressiveness. Like Denny Hamlin did last week in Charlotte, drivers must balance speed and passing while preserving their car.