While NASCAR keeps g-force numbers and crash details confidential to protect drivers’ privacy, some drivers share the numbers from their crashes. But a single number doesn’t tell you everything about crash in the same way that finishing position doesn’t tell you the story of a driver’s entire race.
Some Examples
NASCAR doesn’t release details about crashes to protect drivers’ privacy. Kyle Petty’s 2003 crash at Bristol in 2003 was reported as around 80g. Elliott Sadler’s Pocono crash was rumored to be 86g and Jeff Gordon’s Richmond crash in 2011 was about 40g.
More recently, some drivers have released the data themselves. After Kyle Busch crashed during the Nationwide race at Daytona in 2015, he told the press that he left the track at 176 mph, hit at 90 mph and sustained 90 gs. Â
Ryan Blaney sustained a crash at the regular-season-finale in 2023 at Daytona. You can see its severity by clicking on the link in the twitter post below.
Blaney was involved in another crash in his 2024 Duel before the Daytona 500. He cited the 2023 crash as hitting 70g and the 2024 crash registering 55g.
But what do those numbers really mean?
What’s a G?
The ‘g’ is a unit of acceleration, not force. Acceleration is how quickly you change speed. The time it takes for a car to go from 0 to 62 mph (100 kph) is a measure of acceleration. For example, the Lykan HyperSport can do 0 to 62 mph in 2.8 seconds, which corresponds to:
- An increase of 22.4 mph each second.
- An acceleration of 32.48 feet per second per second.
- Since 1 g is 32.174 feet/second/second, this is an acceleration of 1.01g
Let’s relate this to real life.
- The Space Shuttle pulled 3g on launch
- Apollo 16 pulled 7g on re-entry.
- A Cup Series car going around Bristol experiences around 2.5-3g, depending on speed.
- A good roller coaster will accelerate you at 2-3g.
- The electronics in military munitions have to survive 15,000g.
One ‘g’  is equal to the acceleration of any object due to Earth’s gravity. You are experiencing about one ‘g’ right now. According to F=ma, your weight is the product of your mass times the acceleration due to gravity.
When you experience 3g of acceleration, it’s like your weight increases threefold. If you pull 3g around Bristol, it’s as if your head (which weighs about 12 lbs with helmet) weighs 36 pounds.
Important: Although Earth’s gravity pulls down (toward the center of the Earth), we use ‘g’ to measure acceleration in any direction: up or down, back or forth, or sideways.
Measuring Gs?
Most of the numbers mentioned before 2023 were measured via an accelerometer attached to the car’s chassis. The accelerometer is located near the frame rails, which means it measures more what the car experiences, rather than the driver’s experience.
More recently, some NASCAR drivers have been wearing mouthpieces with built-in accelerometers. IndyCar drivers have traditionally worn in-ear accelerometers; however, NASCAR safety czar Dr. John Patalak feels that the mouthpieces give a better reflection of the actual acceleration the driver’s head actually experiences.
Todd Gordon, on SiriusXM NASCAR radio, said that Blaney’s 2023 Daytona crash gave an accelerometer reading of about 40g, which is much lower than the 70g that Blaney’s mouthpiece accelerometer registered.
But don’t interpret that as meaning that you can just add 30g to the car accelerometer and know how fast the driver’s head accelerates. The driver’s experience depends on his body, his helmet, his head-and-neck restraint device, his seat, and the angle of the hit(s).
Angles are especially important, but they make thinking about gs more complicated. The driver experiences forces that push up/down, left/right and forward/backward. When you hear 70g, that’s the cumulative forces in all directions. It could be all forward/backward, or divided in the three directions.
Without the details of the crash — the specific forces and their directions over the entire duration of the crash — you can’t really know the severity of the crash. For example, the human body can withstand higher accelerations perpendicular to the spine than parallel to it.
How Many G’s Can the Human Body Survive?
It’s a difficult question to answer because people generally don’t volunteer to be accelerated really fast so scientists can see if they survive.
With one exception.
Col John Stapp (Air Force, shown at left) was active in the late 40s and early 50s. We didn’t know how far or how fast airplanes (and rockets) would allow us to go. And even if we could build the machinery, would a pilot or passengers survive?
The military didn’t want to hand over soldiers for him to run experiments on, so Stapp experimented on himself.
That would never happen today because Stapp would have died of old age by the time the paperwork was approved. But back in the 50s, that wasn’t an issue.
The picture shows a test in 1954 where Stapp sustained more than 25Â g for 1.1Â seconds. Twenty-five g might sound small compared to 90g but a driver experiences that acceleration for a couple hundredths of a second. Stapp did it for tenths or full seconds.
The problem with Stapp’s experiments is that acceleration perpendicular to your spine makes your eyes bug out (or in). High acceleration is like putting your peepers on a bungee cord. Stapp’s experiments stopped because he sustained major damage to his vision. See http://www.ejectionsite.com/stapp.htm if you’d like to learn more.
NOTE: This post includes material originally published in 2015, but has been significantly edited and updated.
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