Tuesday, May 26, 2015

COMMENTARY: Harvick Explains The Physics Of Aero Push

"It's always going to exist in racing..."
Kevin Harvick knows the way to Victory Lane at virtually every track on the NASCAR Sprint Cup Series circuit. Apparently, he also has a pretty firm command of the laws of physics.
Last week at Charlotte Motor Speedway, Harvick was asked for his opinion on the topic of “aero push” and its impact on competition. His response was perhaps the most insightful, realistic and non-histrionic in recent memory, and set – at long last – a reasonable bar of expectation for the future of the sport.
“Let’s clarify ‘aero push,’ said Harvick. “Does anybody watch Formula One? It’s been there for years. It’s in Indy Cars. It’s in (all of) racing. If you run behind one of your colleagues… you’re going to have aero push.
“It’s always going to exist in racing,” he said. “Your car is never going to run as fast behind another car as it does by itself. It’s just impossible.”
Harvick, of course, is correct. Whether racing modern-day Sprint Cup Series stock cars, their lumbering behemoth predecessors from the 1960s and `70s, aerodynamics have always played a recognizable role in the sport. We just didn’t know what to call them.
NASCAR Hall Of Famer Junior Johnson is widely credited with discovering the concept of drafting, while attempting to manhandle a boxy, underpowered, year-old Chevrolet around the 2.5-mile Daytona International Speedway in 1960.
"When Cotton Owens came by me, I ducked in behind him coming off the fourth turn," said Johnson in a 2010 interview with reporter Ed Hinton. “When I got down in the first turn, I was running all over him at about half throttle.

“I didn't know what it was, to tell you the honest-to-God truth.”

Despite having only a grade-school education, Johnson knew a big advantage when he felt it. He used his newfound knowledge of aerodynamics throughout the second annual running of the Daytona 500, drafting off faster cars and gaining more than 15 mph over what his car could manage by itself. The tactic allowed him to win the race with a car that – left to its own devices – should have struggled to run in the Top-10.

"Basically I stole the race,” he admitted years later. “I didn't win it."

Since that fateful day in 1960, drafting and aerodynamics have been a crucial – and much discussed – part of NASCAR racing. Over time, teams have learned to massage their cars to maximum the benefits of drafting, eventually reaching a point where bodies looked more like boomerangs than automobiles.
Lynda Petty, late wife of Hall Of Famer Richard Petty, once asked crewmembers why they were loading a crashed race car into their team transporter.
“That ain’t wrecked,” assured The King. “That’s the way we build `em these days.”
Harvick could pass anyone but the leader
NASCAR called a halt to the aero wars a few years ago, mandating body styles that maintain brand identity while blowing identical numbers in the wind tunnel. And NASCAR teams immediately began tinkering with those bodies (as NASCAR teams will do), tugging the fender skirts and pulling on wheel wells to increase aerodynamic stability and downforce, after passing through pre-race inspection.
As NASCAR’s reliance on aerodynamics has increased, competition has suffered. These days, drivers can pass anyone on the race track, except the leader. In this month’s NASCAR Sprint All-Star Race at Charlotte Motor Speedway, Harvick started 25th in a 25-lap segment and slashed his way through the field, all the way to rear bumper of the leader. Harvick’s charge ended there, however, as the aerodynamic advantage enjoyed by that leader kept Harvick’s clearly-faster race car safely in the rear view mirror.
 A similar situation occurred in the race’s final, 10-race Sprint, when Harvick ran down leader Denny Hamlin from 15 car lengths back in just five laps. Hamlin thwarted Harvick’s charge simply by moving up the race track and “taking the air” off the nose of Harvick’s onrushing Chevrolet, gaining 10 car lengths almost instantly and driving away to a $1.1 million payday.

“These cars, over the last 20 years, have become more sensitive in aero push,” said Harvick last week. “In the ‘70s and ‘80s, it was probably there. They just didn’t know it.
“We almost know too much about everything that’s going on now.”
Kevin, you have never been more right.
Aerodynamics isn’t going anywhere. NASCAR’s vast corps of pit road engineers is not about to toss those high-dollar university degrees in the dumpster and forget what they know. The wind tunnels, pulldown rigs and seven-post machines that dot the sport’s landscapes these days are not going to be pushed into a dusty back corner of the race show and covered with a blue tarp. The sport will continue to evolve – rather than de-volve – leaving NASCAR with little choice but to try and rein-in the evolutionary process, while simultaneously searching for a way to lessen the impact of a phenomenon that will never truly be eradicated from the sport.
“It’s a matter of degree,” said Harvick last week. “Maybe it’s impossible to fix, but one would think it’s possible to control.”
Again, he’s precisely right.
Unless the laws of physics are repealed, NASCAR will never completely eradicate the term “aero push” from our vocabulary. To some degree or another, the lead car will always be the fastest car. How much of an advantage that leader enjoys, however, remains to be seen.
Rules can be massaged to minimize the aerodynamic advantage, allowing drivers to play more of a role in the performance of their car. Ironically, many informed observers say that tweaking the rules to force drivers to spend more time off the gas (and up on the wheel), could have a positive impact.
Whether that tweak includes more downforce, less downforce, more horsepower or less horsepower depends on who you ask. There are individuals with impressive racing resumes on all sides of that debate, which is part of why NASCAR struggles so mightily with the decision on what to do.
The good news is that the 1.5-mile ovals have not always been the disappointing, ugly sisters of NASCAR. We’ve raced hard on the intermediate tracks before, and we can do it again.


  1. I do think you can look at the past and see where you once where and get an idea about how to get back. Aro push because a prevalent term in the late 90's. So teams learned how to manipulate body's to fit templates and maxamixe the aro capabilities of the body. As the body modifications progressed so did the clean air advantage. It's also during this time that corner speeds started to escalate. Teams started sealing the cars off to the ground and speeds went up. The faster you run through the corner the more air you need to hold the car to the track. The point is let's get the cars back to an early 90's platform. Befor cars where sealed to the ground, befor body twisting, befor big sway bars. It can be done. There is no reason in today's sport they truly need side skirts, there is no need for a shark fin. There is no need for a off set rear number and flat sides on cars. So take away the side skirts and shark fin, reduce the width of the rear bumper and center it on the car. The profile on the drivers side of the car should also be on the right side of the car. Now you have a car that is a lot less stable though out the corner and the slab side car with all its stabilizers would be gone. Let the down force come from the nose and rear spoiler. Corner speeds would probably be down about 20 mph. I promis you the nose will stick better behind a car at 150/160 vs 170/180. If you take that a step further and limit the big sway bars that tire the front ends of the cars down your probably going to have a race car that the driver will have to hustle around though the corners. Not a bad thing IMO. Last but not least maybe good year could finally build a soft tire because the corner loads would be the lowest they have been in 20 years. I am not an expert by any means. I just know over the years the more the air has been maximized, the the harder it been to pass. So removing everything on the car that maximized and stabilizes the car in air seems to me to be a very easy fix.

    1. Anonymous2:43 PM

      Agree...& Thank You...Cars had aero in the 70's & 80's & 90's & there was passing..Get those fins gone-lose the splitter & spoiler (you know sort of like your factory unit) ..These cars should not have more than 10% increase in downforce over a stock unit & I'm sure this would help the racing..Leave the horsepower alone (cars have throttles & brakes for that) ..Or just keep going like this & lose more fans that are not being replaced..Did ya see that Indy 500? I didn't notice the aero push(draft yes)..That was racing for an entire race(& to think I came from the cart cars to what was then far more exciting Nascar in the late 70's) ..Earner

  2. Anonymous7:01 AM

    Which is right , Harvick saying a car cant go as fast as it can behind a car , or Jr Johnson saying his car could go 15 mph faster ?

    1. Anonymous8:23 PM

      Thanks, glad I'm not the only person who noticed there appears to be a major contradiction in this article!

  3. Anonymous3:44 PM

    Its not complicated. Do whatever it takes to make the drivers lift the throttle (a lot) in the turns. The one's with the best handling cars and the biggest balls will always win!

  4. Anonymous11:53 PM

    Dave, you and Harvick should leave the engineering to the engineers. The lead car won't always be the fastest. Often not at Daytona and Talladega. The Junior Johnson example clearly demonstrates that. That massive contradiction sticks out like a sore thumb in your article and you don't have the education to properly explain it. You should stick with more familiar, easier topics: driver's favourite foods, new seats at Daytona, paint schemes, etc.