2015 Rules and Lug Nuts

Welcome back from the holiday shut down. December in the U.S. is like August in Europe. Everyone you need something from is gone. I’m happy to be back to the regular grind.

Forty-three days till the Daytona 500. The shops are buzzing with activity as everyone adjusts to another new rules package. The engine folks are working overtime dealing with the changes there. The only thing that’s slowed down is planning for on-track independent testing, since that’s been eliminated this year. But more time in the wind tunnel, on the seven-post machine, at the computers.

Pit crews have a number of new issues to deal with this year and they stem from NASCAR’s decision to eliminate the tradition of having one official in each pit box during pit stops. Starting this year, they’ll rely on cameras to provide information about any infractions and calls will be made from a central location where all the camera feeds are monitored.

This change necessitates some compromises. Some rules will be easier to enforce via the cameras, while others will be more difficult. As the NASCAR Insiders point out, one of the less-enforced rules is that teams can’t be on the ground in their own pit stall until their enters the pit box immediately behind theirs.   The Insiders note that when NASCAR tested the system in 2014, they found that this rule was routinely violated, but called by officials only when the violation was blatant.

funny gifs

The gif above come from:  http://www.gifbin.com/988955 and it’s there to illustrate that one of the violations that will be more difficult to enforce with the video system is whether all the lugnuts are on tightly or not. Here’s the verbiage from the 2014 rule book.

Where tire(s)/wheel(s) are replaced, all lug nuts must be installed before the car leaves the assigned pit box area. When a NASCAR Official detects a violation, the car must return to its assigned pit box for inspection.

200610Lowes_TireCloseUpIf a lugnut ends up on the ground instead of on a wheel, that’s pretty obvious and officials would require the team to bring the car back in. (No one ever ‘inspected’ the tire – they just put a lug nut on the lug.)

NASCAR uses a five-stud configuration for their tires. Some sports cars and open-wheel cars using a single, central stud, but NASCAR likes to stick with things that look more like what we have on our cars.

As a side note, one of the disadvantages of the five-lug system is that when a lug nut gets away from the pneumatic air wrench (which spins it pretty quickly), it behaves very much like a bullet when it goes flying. Most people who have spent time on Pit Road have been hit by a flying lug nut. It hurts. Without proper head and eye protection, a flying lug nut could do some real damage.

Teams do everything they can to make getting tires on and off the car as fast and fail-proof as possible.


Notice that you see hardly any thread once the lugs are on. The rules require that the first thread must be visible when the lug nut is installed. The remainder of the lugs are smooth and the outmost portion rounded to enable the wheels to slide on quickly and the lugs to tighten fast. Teams are experimenting with different types of air guns to try to speed up their pit stops.

The lugs are mandated to be solid, one-piece heavy duty 5/8 inch diameter with 18 threads per inch. The lugnut itself is required to be one inch (OD) and a minimum of 0.650 inches thick.  So, if there’s 18 threads per inch and the width of the lug nut is 0.650 inches, then there are (18 x 0.65 = 11.7) just about 12 threads in play.

Yes, teams have been caught boring our the lug nuts so that there are fewer threads that have to catch, which means they go on faster.

The obvious question is: “How many lug nuts do you actually need to hold the wheel on?”  I asked a former tire changer. He gave me a big grin. His answer?

Two. But they have to be the right two.

The two next to each other won’t work very well. Two approximately across from each other would be better. Three would be even better. Two lug nuts aren’t ideal, but five is probably overkill.

Which brings us to the people questioning whether this is a really bad idea on NASCAR’s part because it encourages the teams to do something unsafe – possibly to skimp on making sure that every last lug nut is one-hundred-percent, absolutely positively tight as it can be. Teams will cheat a little now that they’re not being watched, which means we’re likely to have safety issues with wheels coming off.

It’s true that teams may not be as paranoid about making sure they don’t do something they could get called for. But the penalties have been called primarily for missing lugnuts, not those that aren’t completely tightened because that’s very difficult to see – camera or in person.

Plus, it’s in the team’s interest not to leave the lugs loose. If one is noticeably loose, you’re likely to develop a vibration in the wheel and that causes not only a potential problem with the wheel, it can totally freak out a driver into thinking he’s about to have a flat.

We’ve seen tire changers signals to the crew chief that they are afraid they missed a lug — even when the official didn’t see it or call it. A crew chief may call a driver back to check, just because a crash could knock you completely out of a race while checking will only set you back a lap or maybe two.

The rule I’m far more concerned about in terms of safety is that NASCAR will not allow one team to help the team in the next box from over the wall. The origin of the rule is to prevent one team (say a team in the Chase) from getting essentially an extra pit crew member, or allowing their pit crew to go faster because they’re got a safety net in the form of someone else corralling their stray tires.

But, the danger of a tire rolling out of a pit box and being punted by a car is significant. Tire plus wheel is seventy plus pounds. A flying tire can literally kill someone one. NASCAR is going to be more rigorous about ensuring that pit crew members  stay in control of the tires until they are more than half way back to the wall (where, in theory, they wouldn’t roll out into the path of an oncoming car), but I would really hate to see a case in which someone hesitated to stop a tire that ended up posing a threat to the people on Pit Road.

The NASCAR Insiders suggest that there are likely to be a plague of penalties in the first couple of races as the teams adjust to the new enforcement criteria. As usual, they’ll adapt quickly, but keep an eye on Pit Road for the first couple races of 2015.

In only 43 days!

And since I know Moody will be disappointed at the lack of colorful graphics, I’ll leave you with a New Year’s present. When you were toasting in the start of 2015, you probably weren’t paying a lot of attention to the bubbles in your bubbly. Well, a couple fluid dynamicists in France have made a career of studying bubbles and they provided some neat diagrams showing how fluid dynamics works in champagne.


I, of course, will have to procure a couple bottles of champagne so I can check this out myself…

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