Next Gen analysis: Overtightening lug nuts, tire pressure battles and more at Kansas

·6 min read

Editor’s note: Bozi Tatarevic is a professional racing mechanic and pit crew member. He will provide technical analysis for throughout the 2022 season.

The NASCAR Next Gen car made its first visit to Kansas Speedway last weekend and showed us that the overall package continues to impress at intermediate tracks.

As seen earlier in the year at tracks like Auto Club Speedway, drivers had to battle challenging conditions and try to get a handle on lift-off oversteer, along with the increased loads on the left rear tire which caused flats for a handful of drivers. Cars were breaking loose early and the No. 14 of Chase Briscoe experienced a lift-off oversteer condition in Turn 4, resulting in Briscoe spinning and going through the grass. Luckily the grass had been cut overnight which, combined with the splitter height of the Next Gen car, allowed him to drive off without significant damage.

Another spin happened around lap 60 as we saw the No. 99 of Daniel Suárez appear to have a left rear tire go flat and result in a spin. This would end up being a continuing trend as multiple cars would end up losing their left rear as the race progressed and this is likely based on multiple factors. Goodyear released notes before the race that noted the significance of the air pressure in that left rear tire and that could impact the durability of the tire due to the loads that it was estimated to see at Kansas.

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Goodyear shared that the loading of the left rear has increased on the Next Gen car because of the independent rear suspension and aerodynamic balance being shifted more to the rear of this car. Goodyear responded to these increases by recommending that teams add two more psi (pound-force per square inch) to the left rear than what they put in the left front to attempt to compensate for those increased loads.

“The amount of air pressure in the tire should directly correlate to the amount of load on that corner of the car,” Goodyear Director of Racing Greg Stucker said. “If the amount of load increases — like it has on the left-rear of this Next Gen car — you need to increase the load-carrying capability in that tire, which is done via air pressure. If you run below our recommended pressures, the tire can over-deflect, sustain damage and result in an air loss.”

While Goodyear can make recommendations on tire pressures, teams are still free to make their own decision on what they want to run and it is obvious that some are more aggressive than others. The Next Gen car allows teams to change dynamic camber on the rear of the car due to the design of the independent rear suspension and some teams are choosing to be more aggressive with their camber settings which can have a significant impact on the loads seen at the rear of the car. Choosing to be more aggressive on camber typically requires higher air pressure in the tires to compensate and teams are chasing that perfect balance of camber and air pressure, with some appearing to miss it.

Dynamic camber is the angle of the tire relative to the car when it is under load on the track compared to static camber which is the measurement of that angle when the car is sitting still in the paddock or the tech-inspection bay. In addition to the camber and tire settings, there is also a factor of impact loading on the left rear of the car as many cars appear to have a setup that leaves them sitting on the left rear shock at the beginning of a run which results in larger impact loading.

MORE: Cars loaded up, racing three-wide at Kansas

Every team that wants to be fast will chase an aggressive setup and finding the perfect balance is key. It is apparent that some teams have chosen to be more conservative. Cars like the No. 18 of Kyle Busch were seeing issues at intermediate tracks early on in the season but have been more stable in recent races.

While a blanket air pressure recommendation is helpful, it might be a good idea for Goodyear and NASCAR to potentially take some notes from sportscar racing where many series have set up recommendations based on how much camber the car is running. In those cases, the more camber that a car is set up with, the lower air pressure that they are allowed to run since the two have a combined impact on the tire loads. These left rear flats are also self-policing to an extent as teams learn where the limits are and begin to run a bit more conservative as the season goes on.

Pit road also had some chaos. The right rear tire of the No. 43 of Erik Jones was stuck during one of the stops with the wheel not wanting to budge. Based on a review of the incident it appears that the wheel nut was overtightened which resulted in it getting bound up against the wheel and having to be cut off to be removed.

Justin Fiedler, who is the rear tire changer of that No. 43 tweeted that he got the wheel nut too tight in the previous stop and while this has happened in the past, it never created such a large issue. Tire changers have been cautious all season to make sure that wheels are tight because the penalties for losing a wheel are severe. This has resulted in some occasions where wheels have been overtightened, but typically they can be removed even if they require a bit of extra work. In this case, it looks like the steel wheel nut ended up fusing to the aluminum wheel after being tightened and re-tightened during the previous stop.

Based on the information we know of the design of the wheel nut, the wheel, and the wheel gun it is likely a combination of multiple factors that caused this incident, including the hardness of the steel used for that wheel nut along with the amount of torque that the wheel gun produces.  Based on observation of pit stops and how wheel nuts go on and off the hubs, it is likely that they are being overtightened in many cases as the wheel gun likely produces more torque than is required for this combination. Unfortunately, the teams are not allowed to make adjustments to the guns so tire changers have to use their best judgment when they believe that the wheel nut is tight enough.

As we shared recently, there are options to measure the torque of the wheel guns at the moment that the wheels are being fastened that can notify the tire changer and even the crew chief on the pit box when wheels are properly torqued. But those are currently not allowed in the series. Teams and officials are likely taking notes from all of these pit-stop incidents and as with other elements of the Next Gen car, will make adjustments to make them more useful for teams and prevent similar incidents in the future.

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Kansas provided for exciting racing and showed us who has been keeping the best notes since the first few intermediate track races, proving that even though teams are optimizing these cars that there is still room for growth.

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