Race Weekend Central

NASCAR 101: Revisiting Marco Andretti’s Viral Missing Linkage

Last weekend during the NASCAR Craftsman Truck Series Xpel 225 at Circuit of the Americas, something weird happened.

Weird has a lot of definitions, but in this specific case, it takes on the monaker of something that fans simply just don’t see too much.

In the late stages of the race, Marco Andretti was coming down a straightaway far from the rest of the field when his car went spinning.

After a few degrees past 360, Andretti’s car came to a stop in a peculiar manner; his back wheels were nowhere to be seen.

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Unless, of course, fans directed their eyes to about 50 yards away from where the car ultimately wound up.

It was something that many racers, including this former one, have never seen before, and happened with no contact whatsoever. It looked like Andretti’s wheels were under his car one minute and the next they were gone. Mainly because that’s exactly what happened.

After the race, Andretti detailed the feel from inside the car that could give keen-eared fans a window into exactly what occurred.

“(I felt) just big vibrations,” he said. “Really, the brake pedal, throttle, acceleration, brake, just huge vibrations. We were limping around. I didn’t have second gear. I would say I’m done with these character builders. I think my character is built at this point and we’re ready for a straightforward weekend, because I haven’t been able to fight yet this season, and it’s getting a little frustrating.”

Vibrations make sense. What else would cause such a complete collapse of what is otherwise considered to be an integral structure of the racecars?

But why was it vibrating so badly in the first place?

The answer can be found in the welds that hold the entire rear end onto the car itself. There are only a pair of them, and they take a ridiculous amount of abuse during a season, especially on road courses as bumpy as COTA.

When the NASCAR Xfinity Series cars and the trucks experience hard braking from high speeds, they have a tendency to wheel hop. When this happens, the drive shaft and arms of the frame flex and unflex to create and lose contact with the asphalt repeatedly.

That hopping puts stress on the welds that hold the rear end housing underneath the car — and, in Andretti’s case, caused the welds to fail. The harsh vibration Andretti was feeling was more than likely the process of those welds failing and compromising the rigidity of the structure the truck arms are supposed to provide. This is further evidenced by the fact that two U-bolts — horseshoe-shaped bolts with threads at each end — that are meant to aid in holding the rear end housing to the truck were still attached to Andretti’s axle.

That explains what happened, then, but it doesn’t explain why it hasn’t happened before. To begin with, it has to do with the type of suspension used in the NASCAR Cup Series vs. what the lower series use.

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The Cup cars use independent rear suspensions with upper and lower control arms on each wheel. That means each rear wheel can raise or lower independently of the other, whereas the solid axles of the Xfinity and Truck vehicles don’t have that same ability. This is not a new technology, but in order to keep costs lower and abide by series regulations, it’s not a change that the lower series have made.

It is highly unlikely that fans see an instance like this again; it’s more than likely a one-off. Such structurally important welds are typically religiously checked before being used, mileage records are kept up on cars and the cars themselves are picked over with a fine-toothed comb before they ever see the track. For Andretti’s moment to repeat itself, the stars would have to align as perfectly as they did at COTA, and that just isn’t terribly likely.

It doesn’t mean that it wouldn’t make the NASCAR world drop its jaw like it did last weekend if it does happen again, though, does it?

About the author

Tanner Marlar is a staff writer for On3 Sports' Maroon and White Daily covering Mississippi State Athletics, an AP Wire reporter, an award-winning sports columnist and talk show host and master's student at Mississippi State University. Soon, Tanner will be pursuing a PhD. in Communicative Research.

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Christopher

“monaker”
It’s MONIKER. For the love of God will someone provide Frontstretch writers with both a dictionary and a thesaurus.

gbvette62

The fact that Cup cars use independent rear suspension “Doesn’t explain why it hasn’t happened before”. IRS has only been used in Cup since 22, prior to that Cup cars used the same truck arm rear suspension and live rear axle as Andretti’s truck. I also find it hard to believe that COTA is that rough, especially compared to the pounding the trucks took racing on dirt, or at tracks like Watkins Glen or Road America that are subject to much harsher winters and frost heave. Cars and trucks competed numerous times at COTA in Xfinity and Truck and none of them experienced anything like Andretti’s. I have to think the failure to Andretti’s truck was the result of faulty part(s) or weld(s). The track surface may have contributed to the failure, but I doubt it was the root cause.

Chucky

Hard downshifts?

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