Dr. Diandra: Firesuits for race cars

NASCAR Cup cars fire
Photo: NBC Sports

Endurance racer Stephen Cox relates a bone-chilling first-person account (in two parts) of his car catching fire at 125 mph. He was amazed at how the smoke made it almost impossible for him to see his belts or the window net release.

Fire is not unique to any one racing series. When Ryan Blaney’s car caught on fire in the 2018 Coca Cola 600, his crew chief asked if he had activated the fire suppression system.

“Dude, I was trying to get out of it. I didn’t look for the pin. I couldn’t see it regardless,” Blaney told him.

The Next Gen car has had more than its share of fires in its inaugural season. Tyler Reddick experienced the first Next Gen fire at a March test at Kansas. During the season, fire has impacted Chris Buescher, Joey Logano, Cole Custer, Chase Briscoe, J.J. Yeley and Kevin Harvick — all Ford drivers — and Alex Bowman.

After the Indianapolis race, NASCAR mandated an insulating shroud around the right-side exhaust pipes. Officials theorized that contact moved the pipes, allowing them to set fire to the foam inside the door panel.

But fires persisted.

So did driver frustration.

After a fire knocked championship contender Harvick out of the Darlington playoff race, NASCAR issued more technical changes. These modifications are based on a new theory: that small pieces of rubber inside a car start fires.

What causes fire?

Knowing how fire starts is the key to stopping it.

Fire is a chemical reaction between fuel and oxygen in the presence of heat. Engines use spark plugs to combust gasoline. Your body oxidizes glucose and fats in a similar reaction to keep your metabolism going.

Sustaining a fire requires all three components — fuel, oxygen and heat — in quantities sufficient to sustain the chain reaction that keeps the blaze going. Fires stop when one or more of the three components is reduced or eliminated.

Air is about 21% oxygen. Rolling someone on fire on the ground or in a blanket separates the fire from oxygen. That’s the same reason putting out a grease fire by clapping a lid on the pan works. No oxygen, no fire.

Water cools, thus eliminating the heat component. But water won’t extinguish a gasoline fire for the same reason it doesn’t work on grease fires. Liquids like gasoline, paint thinner, etc. don’t mix with water.

NASCAR uses chemical fire suppressants in the car and in the containers safety personnel carry. These chemicals gobble oxygen. A thermally activated extinguisher is required in the fuel cell area, but the suppression system in the driver’s compartment is manually operated.

How firesuits work

The zeroth rule of motorsports safety is: Hope for the best and plan for the worst. That means not just trying to avoid fires, but protecting people if a fire does start.

No material is fireproof. Drivers’ firesuits protect them by providing thermal insulation, being lousy fuel sources and blocking oxygen.

Quilting traps air between a firesuit’s layers. Air is a great thermal insulator, which decreases the amount of heat that can penetrate the firesuit.

Most firesuits are made from Nomex or Nomex blends, although there are increasingly more material options. Nomex may not have the super strength of its sibling molecule Kevlar, but Nomex doesn’t burn: It chars. Charring forms a layer of carbon around the fiber, as shown in the drawings and photos below.

A drawing with photos showing how Nomex creates a char layer around the fiber instead of burning

Carbon is a superb thermal insulator that provides additional protection from the heat. Because the char is not flammable, it doesn’t provide fuel for the fire.

Finally, the expanding Nomex fibers close the holes in the weave of the fabric, as I’ve drawn below. That prevents oxygen and flame from getting to the driver’s skin.

A drawing showing how the expanding Nomex fibers close the holes in a firesuit's weave to prevent oxygen from getting through

All driver gear must be fire-resistant, from headsocks to shoes and underwear. Even patches must conform to standards established by the SFI Foundation. That gear gives the driver about 10 additional seconds before he or she will suffer second-degree burns.

If you want to learn more about firesuits, check out this video I made with the National Science Foundation.

A firesuit for the car

Any material will combust or melt given enough heat and oxygen. Carbon fiber is stable to very high temperatures, but the resins and glues holding carbon-fiber composite together are flammable at lower temperatures.

NBC Sports analyst Steve Letarte broke down the most-recent NASCAR-mandated changes in the video below. The first fix seals places where bits of rubber can get into the car. The second fix replaces part of the polymer right-side door panel — the area closest to the exhaust pipes — with stainless steel.

A video from NBC Sport's Steve Letarte explaining the fixes NASCAR mandated to stop car fires

The only thing I’ll add to the video is that smaller pieces of fuel catch fire more easily. You can put a propane torch to a tire and it won’t burn. But marbles — small pieces of rubber and track grit — have a lot of surface area. That means a lot of places to initiate combustion. That may also be why the problem didn’t make itself known until actual races at tracks that collect a lot of rubber.

NASCAR suggested one more optional fix: intumescent paint. This paint is both a great piece of materials science and fun to say.

Intumescent (in-too-MESS-scent) means expanding, often in the presence of heat. Research on intumescent paint took off after 9/11 and the surprising way the steel in the World Trade Center melted. Intumescent paints are now required in many commercial buildings. They’re also common in drag racing.

Intumescent paint works much like Nomex. Heat swells the paint, but to a much greater degree. The video below shows an example of an intumescent paint used in construction.

A video showing intumescent paint expanding

Also like Nomex, the char cannot become fuel. The example below uses a regular piece of cardboard with and without protective paint.

A video showing how intumescent paint prevents cardboard from burning

NASCAR limits painted areas to where the exhaust passes close to the body panels and the right-side foam. Teams also have the option of painting the door foam.

There’s a small weight penalty, but it’s nowhere as big as the consequences of being knocked out of a playoff race because of a fire.

Corey LaJoie learning in his week with Chase Elliott’s team


Spending this week with Hendrick Motorsports has proved eye-opening for Corey LaJoie.

He will pilot Chase Elliott’s No. 9 car today at World Wide Technology Raceway after NASCAR suspended Elliott one race for wrecking Denny Hamlin during last week’s Coca-Cola 600. This gives LaJoie the chance to drive in the best equipment of his career.

MORE: Corey LaJoie not giving up on his dream 

MORE: Details for Sunday’s Cup race

Working with Elliott’s team also has given LaJoie an inside look as to what makes Hendrick Motorsports so successful.

“I thought that I knew what we didn’t have at Spire Motorsports, but I had no idea,” said LaJoie, who starts 30th after tagging the wall during his qualifying lap. “There’s tools that those guys have, intellectual properties specific to Hendrick Motorsports, that even some of the other teams don’t have.

“But the biggest thing that I noticed was just the people and the attitude of the pursuit of perfection. All the key partner teams across all the (manufacturers) all have the same data, but (Hendrick Motorsports has) an unbelievable way of delegating, taking, compacting and making it just digestible – whether it’s for a driver, an engineer, a crew chief.

“I think the fact that they have four incredibly strong teams individually raises the tide for those guys because when you’re sitting in the simulator and William Byron ran a 33.20 (seconds for a lap) … if you’re running a 33.35 with the same setup, you know you have a tenth-and-a-half under your butt and you have to go find it. And then when I go run a 33.20, William next time is going to want to run a 33.19.

“There’s always a consistently raised watermark on the driver’s end. There’s always a consistently raised watermark on the crew chiefs in trying to build the best setups, and the engineers trying to find the best strategies.

“The inner-team competition is one of the biggest things, and I think there are several teams that have that … the healthy ones are certainly evident. But it’s just the overall structure. We have a Hawkeye (camera-based inspection stations used by NASCAR at the track) … all the things that do the same stuff that Hendrick Motorsports has, but the depth of people, collective focus of the goal and the mission is noticeable and evident. It’s a different world.”

It would be easy for LaJoie to be overwhelmed in this situation. His career has been marked with underfunded rides and trying to make the most of his equipment. He’s having his best season in Cup this year. LaJoie ranks 19th in points heading into today’s race.

LaJoie acknowledges the opportunity he has, but he also can’t let it alter his focus.

“It’s been a wild week,” he said. “I can get all sentimental … (about) my dad subbing in for Ricky Craven in 1998 (for Hendrick Motorsports) and all that sort of stuff. But at the end of the day, when I sit in that thing, I don’t know that NAPA is on it, or the No. 9 is on it.

“I’m going to drive it like I have been driving the No. 7 Chevy and putting that thing 19th in points. It’s been a super fun, successful year so far, and we have a lot of work left to do and things to accomplish over there.”

When he returns to his Spire Motorsports ride after today’s race, LaJoie admits this weekend’s experience with Elliott’s team will help him with his own team.

“How I prepare, how I’m going to engage with my team at Spire Motorsports going forward is going to change,” LaJoie said. “I think I’m going to be able to come in there and just apply and share some of the things I’ve learned over the course of the week with (crew chief Ryan) Sparks and the No. 77 team, as well, and I think we’re all going to be stronger for it.”

Dr. Diandra: Is 2023 the season for a Ricky Stenhouse Jr. redemption?


Coming into 2022, Ricky Stenhouse Jr. had two career Cup Series wins in 364 starts. But both wins — and his career-high 13th-place season finish — happened back in 2017.

Stenhouse was unceremoniously dropped by Roush Fenway Racing in 2020 and landed with JTG Daugherty Racing. He made the news every now and then at a superspeedway but could be counted upon to head up season-ending lists of drivers involved in the most accidents. In the years Stenhouse hasn’t been at the top of the list, he’s been near the top.

DNFs and accidents have plagued Stenhouse throughout his NASCAR career. Jack Roush went so far as to park the Mississippi native in his early days in the Xfinity Series because he tore up so much equipment.

Stenhouse redeemed himself, going on to win two Xfinity championships.

From the way his 2023 season has started, it looks as though Stenhouse might be on a similar mission of redemption this year in the Cup Series.

Finishing races

Stenhouse started the 2023 season in the best possible way – winning the Daytona 500. But drivers from less-funded teams who win early superspeedway races usually settle to the bottom of the rankings by now.

Stenhouse hasn’t. He ranks 13th heading into Sunday’s race at World Wide Technology Raceway.

Standings aren’t as good a ruler this year as they usually are because of drivers missing races and teams incurring penalties. But Stenhouse’s statistics back up his ranking.

Stenhouse has finished every race this year on track, as opposed to in the garage or on the hook. Only Ryan Blaney and Corey LaJoie have achieved the same distinction.

In 11 of those 14 races, Stenhouse finished on the lead lap. That’s the same number of lead-lap finishes as William Byron. Denny Hamlin and Martin Truex Jr. are tied for most races finished on the lead lap with 13 each.

This time last year, Stenhouse had already racked up seven of the series-leading 18 caution-causing incidents he would be involved in for the season. Runner-up Chase Elliott had 15 incidents.

Going into Gateway this year, Stenhouse has been involved in only two accidents (Talladega and Charlotte) and had a tire go out at Darlington.

Approaching his career best

I compare three years in Stenhouse’s career in the table below: the 2017 season — his best to date — along with last year and the 14 races run so far this year.

A table comparing loop data stats for Ricky Stenhouse Jr. showing his path to redemption

Stenhouse’s current average finishing position of 13.5 ties with Christopher Bell for sixth best in the Cup Series. That’s 9.3 positions better than Stenhouse’s 2022 average. He’s even beating his 2017 average by 3.6 positions.

Qualifying results are down a bit from 2017 — but remember that those numbers are from the days when NASCAR allowed multiple practice sessions. Stenhouse is only two positions worse relative to 2017, but 7.6 positions better than last year when it comes to establishing his spot on the starting grid.

Stenhouse’s average running position is comparable to 2017 and 2.8 positions better than 2022. He ranks 20th among full-time Cup Series drivers in average running position. Although it’s an improvement, it’s still more than double William Byron’s series-leading 9.1 average running position this year.

More interesting is the difference between Stenhouse’s average running position his average finishing position. Some drivers run better than they finish. Stenhouse is doing the opposite.

In 2017, Stenhouse finished about 1.4 positions better than he ran. This year, he’s gaining an average of about five positions from where he runs.

One might argue this gain results from the plethora of late-race incidents this year that have removed drivers in the front of the field from contention. But Stenhouse deserves credit for putting himself in a position to benefit from those events.

Stenhouse’s green-flag speed rank is 11th among full-time Cup Series drivers. His 15.3 average, however, is 1.7 positions worse than 10th-place Kyle Busch. Still, it’s impressive that JTG Daugherty is right there in the mix with much better-funded teams. William Byron again has the best average green-flag speed rank at 7.9.

Consistently strong finishes

It’s not uncommon for a mid-pack driver to win a superspeedway race. But Stenhouse’s Daytona 500 win appears to be something more. The table below summarizes his wins and finishes for the same three years.

A table comparing finishes for 2017, 2022 and 2023 showing Ricky Stenhouse Jr's redemption attemptsThe difference between last year and this year is striking.

In 2022, Stenhouse finished in the top 20 in 12 of 36 races. He’s already matched that mark this year. He earns top-20 finishes 85.7% of the time in 2023 compared to 33.3% last year. Top-20 finishes aren’t the same as contending for a championship. But they’re a first step.

Stenhouse finished 2017 with nine top-10 races. With about 60% of the season remaining, he’s already earned five top-10 finishes this year.

What’s changed? The Next Gen car is one factor, but it didn’t make much difference for Stenhouse last year. I would point instead to Stenhouse’s reunion with Mike Kelley as his crew chief.

Kelley co-piloted both of Stenhouse’s Xfinity championships in 2011 and ’12. Although Kelley worked with Stenhouse and previous crew chief Brian Pattie since 2020, this is the first year Kelley is back up on the pit box.

Together, they’re basically halfway to matching Stenhouse’s best year.

And another step closer to redemption.

Portland Xfinity race results, driver points

Portland Xfinity results
Photo by James Gilbert/Getty Images

Cole Custer went from fourth to first on the overtime restart when the top three cars made contact and went on to win Saturday’s Xfinity Series race at Portland International Raceway. Custer is the 10th different winner in 13 races this season.

MORE: Portland Xfinity race results

MORE: Driver points after Portland Xfinity race

JR Motorsports took the next three spots: Justin Allgaier placed second, Sam Mayer was third and Josh Berry was fourth. Austin Hill completed the top five.

John Hunter Nemechek remains the points leader after 13 races. He has a 14-point lead on Hill. Nemechek leads Allgaier by 44 points.

Cole Custer wins Xfinity race at Portland in overtime


Cole Custer held off Justin Allgaier at the finish to win Saturday’s Xfinity Series race in overtime at Portland International Raceway. It is Custer’s first victory of the season.

JR Motorsports placed second, third and fourth with Allgaier, Sam Mayer and Josh Berry. Austin Hill finished fifth.

MORE: Race results, driver points

Custer went from fourth to first on the overtime restart when Parker Kligerman, who restarted third, attempted to pass Allgaier, who was leading. Sheldon Creed was on the outside of Allgaier. All three cars made contact entering Turn 1, allowing Custer to slip by. Creed finished seventh. Kligerman placed 14th.

Custer won the second stage when John Hunter Nemechek made contact with Creed’s car while racing for the lead on the final lap of the stage. The contact spun Creed and Custer inched by Nemechek at the line.

Early in the final stage, Creed gained revenge with contact that spun Nemechek, who went on to finish 10th. A few laps later, Nemechek and Joe Gibbs Racing teammate Sammy Smith had issues. Smith spun Nemechek. After getting back around, Nemechek quickly caught Smith and turned into Smith’s car, damaging it.

STAGE 1 WINNER: Sheldon Creed

STAGE 2 WINNER: Cole Custer

WHO HAD A GOOD RACE: Despite the contact on the overtime restart, runner-up Justin Allgaier managed to score his fourth consecutive top-three finish. … Sam Mayer’s third-place finish is his best on a road course. … Austin Hill’s fifth-place finish gives him four consecutive top-five results.

WHO HAD A BAD RACE: Daniel Hemric finished 33rd after a fire in his car. … Riley Herbst placed 32nd after an engine issue. After opening the season with six top 10s in a row, Herbst has gone seven races in a row without a top 10.

NEXT: The series competes June 10 at Sonoma Raceway (8 p.m. ET on FS1).