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I’m a NASCAR Tire Specialist

Without the benefit of on-board computers that you’ll find in other racing series, the crew chief of a NASCAR team relies on the feedback provided by a driver when trying to set a car up. In addition to the driver, there is another voice that the crew chief listens to for information on the car’s handling – that of the tire specialist. You won’t believe just how much a tire can tell you about the mood of a race car.

In this interview you’ll hear from Patrick Mullen, tire specialist for our No.11 FedEx NASCAR Sprint Cup team. He’ll tell you what his job is like and everything you need to know about the Goodyear Eagles we race with.

Tell us a bit about yourself. Where are you from, how did you get into racing?

I grew up in upstate New Jersey where my family and I raced Modifieds at the Wall Stadium (an historic track that has seen many NASCAR-sanctioned races in its time). My brother Ronnie still races cars in that area and I love to keep up with how he’s doing in his #39. I moved to North Carolina in 1999 to pursue a job in racing.

How many sets of tires do you deal with on any given race weekend?

On a typical weekend when the big race is on Sunday we will usually fly out of North Carolina on Thursday afternoon. When I get to the track on Friday morning we get straight to work. NASCAR only gives us a certain number of sets for Friday through Saturday, so I have to be sure to designate a certain set for Practices and a set for Qualifying. NASCAR gives us 8-10 sets for the race depending on the track. Those can’t be used for practices or qualifying.

What is it like to be a tire specialist during practice sessions?

Practice is when we really get to see what the car is doing and figure out how to make it faster. I do a lot of measuring and gauging. We practice for qualifying and racing and tire pressures vary greatly between those two environments. Our race tire pressures start low because they will build up throughout a tire run. For a long green flag race run, we have a targeted tire pressure that we’ve determined with get us maximum grip. For qualifying runs I’ll set the pressures higher so they will reach that target pressure more quickly.

Besides the tire pressure, I’m always checking the tire wear and the tire temperature. In regards to wear, we look to see if each tire is wearing more on the inside, middle, or outside of a tire. This will tell us if the car has too much or too little camber, pressure, wedge, etc. Temperatures can tell us similar things.

What kind of tools do you use at the track and how do they work?

My list of tools includes:

  • An air pressure gauge that can make fine adjustments to the pressure (we usually work in tenths of a pound or air, not pounds.
  • A tire temperature gauge with an 8th inch needle that sticks into the tire to take the temperature. We check the inside, middle, and outside temps.
  • Infrared temperature gun to check the track surface temperature.
  • Valvecaps.
  • Extra tire cords.
  • A valvestem remover.
  • Torch and scraper to remove the excess rubber that collects on the hot tire. I need to clear that to get to check the wear.
  • A Wear guage. Each tire has several indentations across the surface of the tire. The wear guage has a small pin that goes into these holes. The sooner the pin hits the core of the tire, the more that section has worn.
  • Paint pens which are used to mark different reading directly onto the tire.
  • A Computer for keeping logs of tire readings.

We always see a lot of numbers either stamped or written on a tire. Can you tell us more about those?

Typically I’ll mark several things in yellow (which is my color of choice):

  • One is the wheel number. After a wheel has run 5,000 miles we retire it. Marking this helps us keep track of that.
  • On the tire I will note the spring rate number. A tire’s spring rate is the amount of pressure needed to compress the tire one inch. This comes into play because the amount of spring rate in a tire can determine how much of the tire makes contact with the track.
  • You’ll also see a serial number on each tire that is molded into the tire during production. This number tells us the work rotation the tire was created under, the date it was made, and the shift number (these become important when we try to match tires together to make a set).
  • The most crucial number is the circumference number. To measure this, we inflate the tires to Goodyear’s recommended pressure and then measure the complete circumference. Since we are usually turning left, we stagger the tires by putting the larger ones on the right side, making it easier to turn left.


So then what is a “matched set” of tires?

The name of the game is consistency. That’s what wins races. We want a set of tires where each tire is as close to the other three as possible. This eliminates variables in how they grip the track. We don’t want any unexpected variations in tire behavior. A set is matched up when we get four tires with sprint rate numbers and serial numbers that are close together.

Race days must be crazy for you. What are they like?

Some tracks limit the amount of time you have with your tires. At Richmond for example, we have 7 hours to prepare 8 sets of tires. This means measuring and recording all of the data, matching the sets, and marking wheel weight positions. Another things we do is purge the tires of air. Normal oxygen collects water easily, and we don’t want water in our tires so we drain the oxygen out and replace it with nitrogen (a dry air). Then we set it to race pressure and measure the circumference number. We have to get this done in time for the tire changers to come in and glue up their lugnuts. Thankfully our spotter Curtis helps me get this done.

We typically get Mondays off. On Tuesday and Wednesday I am busy getting paperwork together from the previous week to deliver to the crew chief and engineers. I’m also responsible for cleaning the tool boxes each week. I’ll go through them and tear down, clean, and reassemble certain tools like the jack.

Thanks for reading about our tire specialists! If you have any questions leave them for us in the comments!



Thanks so much for this inside view.Very interesting.


Very good job patrick.keep up the work n win some races .go # 11.

J Robert

You talk about “air” in the tires..being new to NASCAR, I thought I read where they actually use nitrogen and not “air” in the tires…


Is Goodyear totally responsible for the tire compound for each track or do the race teams also have input.


Goodyear has several tire tests throughout the year where they select one team from each manufacturer to partake. Drivers and team provide important feedback to Goodyear which they then take into consideration when developing a tire compound. Great question!


my husband said that the tire sets that are delivered are all identical.
i had the impression that hard and soft set were delivered. stagger taken into consideration in both opinions.
could you clear this up please.


I purchased a racing slick good year eagle 1 is there a way to tell what race it came from and driver?


GOODYEAR EAGLE # 1 tire bar code 00378614 any idea what car this was off of im told dale Sr?


I was at Talladega this past weekend and observed two different “lubricants” used on the inside of the threads just as they got ready for pit stops. The first was a grey goo. It looked like graphite paste or molly graphite lube. The second was a brown liquid in a squirt bottle. I saw the bottles used in nearly every pit and saw sticks with the paste on them most places but never saw that being used. Just wondered what those were. Good article.. thanks.


I have a NASCAR used race tire and the used rubber smell won’t go away. I would like to make it a base for a party table with tall bar stools. But the used rubber smell will not go away. So please can you help me with this. Thank you,


what is the tire pressure initially …..????


What type of gauge do you use for measuring tire pressure? Are they calibrated and if so how often?