What we Know about the Abnormal Tire Wear at Bristol

The Bristol 2024 race set lead change record for short tracks, but only because of abnormal tire wear. Let’s investigate why.

How Were the Tires Different?

They weren’t.

The Bristol tire codes (D-5170 and D-5206) are the exact same ones used at the 2023 fall Bristol race. In fact, the extra set of tires Goodyear released to the teams were left over from the 2023 fall race.

One might wonder whether it’s possible that there was a mistake in the tire manufacturing. I very much doubt that. Goodyear has multiple quality assurance checks during manufacturing and each tire is individually inspected before being released. There is a vanishingly small probability something was wrong with that many tires.

How was the Track Different?

Bristol used ‘The Resin’ in the lower groove rather than the PJ1 TrackBite applied last year. Greg Stucker, Goodyear’s director of racing, explained that they made the switch because of a February 2024 tire test at Bristol.

That test included the first trial of wet weather tires at Bristol. Because of Bristol’s extreme banking, it doesn’t run the typical short-track package. The idea was never to race in the rain at Bristol, but to allow 36 race cars to help dry the track out more quickly if it did rain.

At the test, they learned that PJ1 became prohibitively slippery in the wet. Cars moving too slowly could slide down the banking and crash.

Stucker noted that there wasn’t much difference in track temperature from fall 2023 to spring 2024. That leaves the change from PJ1 to ‘The Resin’ as the major difference between fall 2023 and spring 2024.

What’s the Difference between PJ1 and ‘The Resin’?

Even before the Next Gen race car, some tracks started using track preparation compounds to increase grip in one or more lanes. Tracks owned by Speedway Motorsports, Inc. (SMI) started the trend using PJ1 Track Bite. This compound is a traction-enhancing liquid originally developed by the Sperex corporation as a high-temperature coating for NASA.

Sperex spun the material off to its VHT label. That product was primarily purchased and used by drag racers. In 1989, P.J. Harvey purchased the product (and other Sperex) and marketed it under his own brand: PJ1 Track Bite. The chain of custody explains the varied names for the compound.

International Speedway Corporation (ISC, which is owned by NASCAR) went with a different material: VP CTR Circle-Track Resin. VP is the company the developed and sells the materials. They also make resins for drag racings, so the CTR Circle-Track part tells you this this is for ovals.

It’s a little misleading to call the latter ‘The Resin’, because PJ1 Track Bite is also a resin, but—

Whoa. Hold On. What’s a Resin, Anyway?

Technically, a resin is a solid or very thick liquid that can be converted into polymers. They can be natural, like pine sap, or synthetic, like the compounds being used on race tracks.

Rosin, like you’d use on a violin bow, is a solid resin. Frankincense and myrrh are both resins; gold is not. Shellac is a resin that comes from insects.

Natural resins were discovered first. Once people figured out what made them useful, they started making them in labs so that they could control the properties and use them in different situations.

OK. Go On.

Thanks.

So we really ought to differentiate between the VP CTR Circle Track resin and the PJ1 Track Bite resin. Not just because they are two different resins, but because they work in two very different ways.

• PJ1 Track Bite makes the track stickier.
• VP’s CTR Circle Track Resin makes the track rubber in faster. Or at least, it has at every other tracks where it’s been used.

Didn’t NASCAR Check if there was a Difference between Resins?

Goodyear runs a friction tester around the track multiple times each race weekend. A truck towing the friction testing device records the friction at each spot on the track. A GPS allows them to generate a map of the track and the traction.

Goodyear has this data for each track and multiple races. They share the information for parts of the track with the teams. They didn’t see anything out of the ordinary after the final friction test before practice and qualifying. If they had, they would have done something.

So Why Did the Tires Wear So Much?

No one knows the answer to why there was so much tire wear at this race. But I can guess at what Goodyear is doing to try to figure it out.

• I’m sure they did more friction testing than usual after the race so that they can compare the conditions with those after the fall 2023 race.
• Once they realized there was something different, I suspect that Goodyear’s tire engineers made more temperature measurements than usual. That’s data that can only be captured at the track.
• Teams share their setups with Goodyear, so they’ll be looking for whether all the teams were doing something different with caster, camber, suspensions, etc.
• They’ll do more-intensive-than-usual studies on the tires that come back from the track, especially as regards abnormal tire wear. There were a couple different things going on, from cording to graining. A different type of mechanism is responsible for different types of tire failure. They’ll look at both the tires that failed quickly and those from drivers who kept their tires in better conditions.
• Is there a different mechanism when the VP resin is used on concrete vs. asphalt?

One of the consequences of collecting a lot of data is that there is a lot of data to be analyzed. I’m not expecting a fast answer, but I’ll certainly let you know when there is one.