Tire Practicecheck

Everything You’ve Ever Wanted To Know About NASCAR Tires

One of the coolest parts of my job is the behind the scenes access. I can pretty much go wherever I want at the racetrack and talk to anyone. I just can’t get in the way, and I have to make sure I’m not standing on an air hose during a pit stop.

Seriously. Don’t stand on the air hose.

For a newbie to NASCAR, like me, there’s been no better way to be introduced to the sport. The folks on the #39 race team and Stewart-Haas Racing are always willing to talk and explain anything.

So, when I found myself at Las Vegas Motor Speedway for the Kobalt Tools 400 watching the practice, I was intrigued when I saw one of the crew guys working on the tires.

I asked him what he was working on, and after finishing he filled me in.

The crew member was Jeff Zarrella, tire specialist for the team. He was using a portable torch to heat up the rubber on the tires to expose rows of tiny holes. Once the holes were exposed, Jeff would take some measurements and write a series of numbers on the side of each tire.

The tiny holes are called wear pins. Five holes, 3/16 of an inch in diameter, run the width of a tire, straight across for left side tires, angled across for right side tires.

Why the difference? Just to tell them apart. Pretty straightforward.

Before the tires are used, the tire specialist uses a gauge to determine the depth of the wear pin to the 32nd of an inch and records it on the side.

When the tires come off (usually after about 20 practice laps or 35–100 race laps) the tire specialist uses a torch to heat up the rubber and scrape off the excess with a putty knife. Using the wear pin gauge, he records the depth when they’re done.

Viola! Now we know how the tire has worn and the pattern in which it’s worn.

From there, the crew chief and driver can make better-informed decisions of tire pressure to get the best possible feel on the track.

And that can be the difference between winning and losing.

Bonus nugget of tire info?

Ever wonder what those little rubber, hair-looking things that stick out of your tires are when you get them new?

These thingees:

A quick search through the Interwebz will reveal that they are the leftovers from the injection moldings that form the tire.

Now combine a sport like NASCAR that places the utmost value on speed, where a hundredth of a second can be the difference between winning and losing, and you’ve got an issue. Anything that can be a possible drag on the car has to go.

Tiny rubber hairs have to go. At the restrictor plate races like Daytona and Talladega, the tire specialists will clip all the hairs of all the tires before the race, somewhere around 1400 snips.

That’s a whole lot of snips.

Extra bonus nugget of tire info?

Maybe you’re wondering why the tire on your sedan you take to work and back has a fancy, shmancy tread on it, while the Goodyear Eagles on Ryan’s #39 car are completely flat?

Simple. Flat tires mean more rubber on the road. More surface area on the road means more stickiness to the road. And when you’re screaming by at 195 mph on the track, sticking to the track and not becoming airborne is kind of important.

So why does your car have the aforementioned treads? You drive in rain, and the treads are necessary for your car not to slip and slide all over the road.

What does Ryan do when it rains while he’s in the #39 Chevy? Waits for it to stop raining.

Again. Pretty straightforward.

OK, folks. Final extra bonus nugget of tire wisdom.

Inside your average NASCAR Goodyear Eagle tire is a whole other tire (not to mention nitrogen instead of plain, old air). Since 1966, racing tires use a “tire-within-a-tire” concept that allows the cars to get back to the pits in case of damage. The inner liner safety spare weighs 10 lbs and is usually inflated 12–25 lbs higher than the outer tire.

What else do you want to know about tires? Or about the inner workings of a Sprint Cup Series car? Let us know, and we’ll do our best to uncover all the secrets for you!

Joel Jarvi

Despite being the father to 3 kids, Joel refuses to wear socks with his sandals, buy gas station sunglasses, or carry his cell phone in a leather holster on his belt. Joel is truly working in his dream job and hoping this isn’t actually his dream INSIDE a dream job. [INCEPTION SOUND]

This Post Has 10 Comments

  1. Rick Myers

    I have been to 2 Daytona 500’s in a row that got rained out, so I had to go to work on Monday with no refund for the ticket (grrrrrrrrrrrrrrrrrrr!). All other motorsports racing continues in the rain except Nascar. Just how expensive would it be to install windshield wipers, tail lights and have a few sets of treaded rain tires to keep racing? I don’t “call in” to work because it’s raining…how many Nascar fans spend money for nothing because of this?

  2. Eddie

    Wow this is some good stuff! Thanks! I’ve always wanted to know how even with loctite keeping the lug nuts on the wheel when doing pit stops, how are the lug nuts not pushed off when the wheel studs come through. Besides the tires I’ve always wanted to know how the driver’s cool air boxes function, it it battery powered?

  3. Terry L. Hynicker


    Nice article on tires. But I think that the Final nugget of tire wisdom is somewhat incorrect. “Inside your average Goodyear Eagle tire is a whole other tire”. These tires are anything but average. If you go down to your local Goodyear dealer and get a set of eagles for your daily driver they DO NOT have a whole other tire inside. The tire inside the tire I think is exclusive to Racing Tires.

    The eagles that you buy at your local Goodyear store are great tires and are made of a softer rubber compound then say other All-Season Tire. This helps help the “Stick” on the street. Also for the most part when someone says that they have Goodyear Eagles on their daily driver you thing high speed/high performance tire.


    1. Joel Jarvi

      Terry – You are absolutely correct! The “tire-within-a-tire” safety feature is definitely exclusive to NASCAR tires. I amended the article to make that distinction.
      Thanks so much for reading!

  4. Stacia R.

    Thanks for the insight in tires.
    How can the drivers run the same line on the track, does it take 100 percent concentration, habit, or does the car simply follow the lines easily over and over again. I wouldn’t be able to hold concentration, especially on the short tracks, for hours.

  5. Aaron

    Eddie – That isn’t Loctite holding those lugs on. It is actually silicone. The reason they use silicone is that it has flex so as they drive on the first lug, the elasticity of the silicone stretches keeping the lug on the tapered post.

    However they do fall off from time to time. You’ll see the tire guys with lug nuts siliconed to their mask, on the back of their gloves or on their belt. This way instead of fumbling with a dropped lug nut, they use muscle memory to keep moving.

  6. Sean Collins

    On the tires that are used, how would I be able to purchase on with Ryan’s signature on it?

    1. Joel Jarvi

      Sean – The teams all return their race used tires to Goodyear after every race for analysis. You can SOMETIMES find them on eBay and other sites on the Internet, but they can be very difficult to authenticate.
      I’d maybe check racemetal.com as well.
      Thanks for the read!

  7. Ken Palmersheim

    I have a Matt Kenseth autographed tire, with a signed certificate of authentication from the July 2010 Daytona Race. Is there a site on which I can list it for sale. My goal was to buy a round glass top and make a coffee table for the family room to display it, but my wife says no.



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