Dr. Diandra: Darlington tire fall-off — the good kind


Engineers call the effects of tire wear ‘tire fall-off’. This can lead to confusion, especially when NASCAR is dealing with tires literally falling off cars.

Tire fall-off — the good kind — played an important role in last week’s Dover race. Given Darlington’s aggressive track surface, expect it to have a major impact on this week’s race, too.

What is tire fall-off?

Friction with the track wears down tires. Rubber sticks to the track, balls up to form marbles, or gloms back onto the tires during cautions. Tire wear requires teams to use multiple sets of tires during a race.

The ideal tire would grip like crazy and never wear out. Unfortunately — like perpetual motion machines and universal solvents — the laws of physics preclude the perfect tire.

That means Goodyear faces the classic Goldilocks problem at each track. Tires that are too soft wear out too quickly and become a safety issue. Tires that are too hard don’t wear out, but they also don’t offer much grip.

Visualizing tire wear

The best way to “see” tire fall-off is by examining lap times. Let’s use Chase Elliott‘s race from Dover last week as an example. Below, I plot his lap times and running position as functions of lap number. I’ve also shown where cautions occurred by shading those laps yellow.

Two scatter plots showing the lap times (upper) and running position (lower) for Chase Elliott in the Spring 2022 Dover race

Lap times trend upward for each green-flag run of more than a handful of laps. There are variations from lap to lap, of course. That’s why I include running position. A driver’s lap times are highly dependent on whether he’s driving in traffic or not.

Elliott changed tires six times, during pit stops on laps 42, 123, 160, 191, 244 and 326. You can tell tire changes because there’s a sharp, one-lap blip upward in his running position.

Elliott led the last 52 green-flag laps of the race, mostly unimpeded by traffic. Let’s isolate these laps and, since he ran P1 the entire time, we can ditch the track position graph.

I’m also inverting the y-axis so that down means slower.

A scatter plot showing Chase Elliott's lap times for the last 50 laps of the spring 2022 Dover race

Flipping the axis makes the graph a little more intuitive because now you really see the times falling off.

If you’re wondering why I plot time instead of average lap speed, it’s because NASCAR measures time. They infer speed by dividing track length by time. Because drivers don’t drive the same distance around the track each lap, lap time is a more accurate quantity.

You’ll hear people talk about ‘two seconds of tire fall-off.’ Be careful. That’s doesn’t tell you anything. Fall-off is how much lap time increases over some number of laps. It’s a rate, just like miles per hour or revolutions per minute.

Elliott’s last run at Dover started with a lap time of about 23.4 seconds at Lap 350 and increased to about 24.4 seconds at Lap 400. That’s one second of drop-off over 50 laps. Elliott had a big lead at this point and didn’t have to push his tires very hard. A driver using up his tires trying to pass or defend a position can experience even higher fall-off.

In this year’s Martinsville race, where abnormally cold temperatures hurt tire performance, Elliott lost only one second of lap time in the course of leading 90 laps.

What determines how much tire fall-off there is?

An asphalt track is composed of an aggregate mix (rocks) and a binder (the black tarry stuff holding the rocks together.) As a track ages, the binder erodes and the aggregate edges round. Aging changes the grip and how the surface wears tires.

Many variables contribute to tire fall-off, but Goodyear director of race tire sales Greg Stucker explains that “the biggest factor in tire fall-off is the track surface.” For example: Concrete is less porous, so it wears rubber from tires differently than an asphalt track.

But every asphalt track is different as well.

NASCAR ran the same tire set-ups in 2021 at Darlington, Charlotte and Homestead. The 1.5-mile Charlotte track produced about one second of fall-off in 40 laps. Homestead is also a 1.5-mile track, but drivers there experienced about 3 seconds of fall-off in 60 laps. Darlington, with its rough, 2008-era surface, resulted in 3 seconds of fall-off in 30 laps.

The upside

High tire fall-off introduces lots of strategic possibilities.

If new tires aren’t much of an advantage (i.e. not a lot of fall-off), then there’s no point pitting unless you need fuel. But if new tires can give you a tenth-of-a-second advantage per lap, it might be worth short pitting. Short pitting is coming in for tires in the middle of a fuel run hoping to gain positions by virtue of having new rubber.

The crew chief must balance the risk and reward of pitting. How many positions will the team likely lose by coming in? How do other teams pitting (or not pitting) affect the plan? That decision will also depend on how many laps are left in a stage or the race.

The decision is complicated by the fact that tire fall-off isn’t uniform. That, Stucker says, is because there are so many different variables involved.

“In some cases, tire wear is linear,” Stucker explains. “In others, we see a rapid decline, then a slower decline.”

But even two different drivers on the same track with the same tires can experience different fall-off rates depending on their cars’ set up and how aggressively they’re driving.

Although Chase Elliott’s tire fall-off may be one second over 50 laps, that doesn’t mean he loses the same amount every lap. At Dover, tires wear faster in the first stages of a run, then the fall-off decreases a little.

I’ve tried to illustrate this by drawing two straight lines in Elliott’s Dover data. The left line was fit to the first 20 laps and the right line to the last 20 laps.

A scatter plot of Chase Elliott's lap times, with a linear fit to the start and the end of the green-flag Dover run.

The first line is steeper than the second, indicating that the tire fall-off is faster in the early part of the green-flag run than in the later part.

But again, if another driver had closed the gap in the last 20 laps of the race, Elliott’s tire fall-off might have gone up because he would have had to race harder to preserve his lead.

This non-linearity makes the crew chief’s decision even more complicated. If the tires wear really quickly in the first 10 laps, the advantage of new tires lasts for a shorter time. Can the driver get to the front before he’s worn out the tires enough that someone else can pass him?

Tire fall-off may make crew chiefs pull out their hair, but it’s a good thing for those of us watching the race because it adds one more complication to the competition.

Seven Cup drivers entered in Xfinity race at Sonoma


Kyle Larson is among seven Cup drivers entered in Saturday’s Xfinity Series race at Sonoma Raceway.

The race marks the first time the Xfinity Series has competed at the California road course. Teams will get 50 minutes of practice Friday because this is a new event on the schedule. That additional time will give those Cup drivers more laps on the 1.99-mile road course.

MORE: Sonoma Xfinity entry list

Here is a look at what Xfinity rides the Cup drivers will pilot this weekend:

The race is scheduled to start at 8 p.m. ET Saturday.


Winners and losers at WWT Raceway


Winners and losers from Sunday’s Cup race at WWT Raceway:


Kyle BuschWins the pole, leads the most laps and holds the field off over the last five restarts to win the race. He scored six playoff points, giving him 16 on the season, second only to William Byron’s 17. Busch left Joe Gibbs Racing after last season for Richard Childress Racing. Busch’s three wins this year equals what JGR has done so far.

Ryan BlaneyHis sixth-place finish moved him into the points lead. He last led the points after the spring 2022 Richmond race. Blaney also won a stage Sunday to collect another playoff point. He has seven this season.

Kyle LarsonFourth-place finish was a big turnaround after struggles earlier in the race. It has not been easy for this team the last few weeks. He has three top-five finishes and four finishes of 20th or worse in the last seven races.

Daniel SuarezHis seventh-place finish moved him up two spots to 16th in the standings, the final playoff transfer spot at this time.


Ross ChastainHe finished 22nd for his third consecutive result outside the top 20. He entered the weekend leading the points and fell to fifth afterward. He is 29 points behind new series leader Ryan Blaney with 11 races left in the regular season.

Tyler ReddickRebounded from an early spin to lead but had his race end after a brake rotor failed. He was one of four drivers eliminated by brake rotor failures. The others were Carson Hocevar, Bubba Wallace and Noah Gragson.

What drivers said at WWT Raceway


Here is what drivers had to say after Sunday’s Cup race at WWT Raceway:

Kyle Busch — Winner: “Just the restarts kind of went our way. We were able to get through on the outside on that one and push (Kyle) Larson out, then he took bottom of (Turns) 3 and 4, I was able to carry the momentum around the high side to take the lead. That was really important. I think that was kind of the key moment of us being able to win today. Being able to control the rest of the restarts for the rest of the race. Kyle is one of the best. It’s good to be able to sit up here and race hard with him, being a Team Chevy partner. He gave me great respect, I appreciate that. That will be given back down the road.”

Denny Hamlin — Finished 2nd: “Yeah, I thought we were super dialed if it was 95 degrees like it was supposed to be with those delays – it kind of took away from the advantage I thought that we had. I’m proud of this whole Sport Clips Toyota team – pit crew did a phenomenal job keeping us in it and doing really good on the money stop with about 60 to go. We are going to have to wait another to get that 50th (win).”

Joey Logano — Finished 3rd: “I’m proud of the fight. We were mediocre – just outside the top five all day long. There was a group of cars that were a tick better than us. Then we executed at the end and beat a few of them. We tried some new things from last year, and we learned some lessons. But overall: Good. We needed a solid run. We’ve been going through hell here lately. So, it’s nice to get a top five, third place, and some points there in each stage. Good day.”

Kyle Larson — Finished 4th: “Proud of the effort today. It’s been a couple tough races. We’ve been so good all year long and the last few have been pretty bad and we’ve had to work on it quite a bit. The team got us in a place where we could contend for the win, so you can’t ask for much more than that. …  I wish I would have done a better job. When I was the leader, I hadn’t been at the front all day, so I didn’t know what to expect. I didn’t know where people were running on restarts, and I didn’t know how hard they could go. I just got kind of caught off guard and lost the control.”

Martin Truex Jr. — Finished 5th: “Started off the race near the front and stayed there through Stage 1 and thought we could get a little bit better and maybe have a shot at the couple, three in front of us. We had a pit road penalty and had to go to the back, and it was just an uphill climb from there. Just really tough to get through the field. We got some damage from when someone’s brake rotor exploded, that slowed us down even more. Really with all we went through today, a top-five is a really good day for us. I’m proud of the effort.”

Ryan Blaney — Finished 6th: “We ran pretty good today. Won the second stage which was good, second in the first stage. Just kind of lost track position, lost the lead. Through a couple stops and restarts, we could just never really get it back. I thought that (Kyle Busch, Denny Hamlin) and I were similar. It was just a matter of who was out front. I just got a bad restart at the end and fell to sixth. But overall, it wasn’t a bad day. It was a good points day too, and we’ll keep going.”

Daniel Suarez — Finished 7th: “The entire weekend was very solid for us. We barely missed the second run in qualifying and really, we missed it because of me and not because of the car. The car was capable of advancing. In the race, the car was strong right away. It was fun today and we really needed this as a team. We needed a result that we deserved, and I felt like lately it’s been a little difficult on us when it comes to that. Today, I felt like we deserved a top-10 or top-five and we came home seventh, so we will take it.”

Michael McDowell — Finished 9th: “We kind of learned last year that track position is super important. Taking two tires was an option last year, so we knew it’d be one this year. We did it early on and got track position, but we got spun out. So, went all the way to the back and then we put four on, and then you’re just buried back there. So, we had to go for it again, put two on and just left two on. We never took four again. There were a lot of laps on the left-side tires, but track position was super important. We had a great FR8 Auctions Ford Mustang, so I knew we could kind of hold our ground. Those last few cautions kind of hurt us a bit, but still came away with a Top-10. So, it was a good day.”

Chris Buescher — Finished 12th: “That was a long day – long race. There were a lot of cautions and red flags. It really started yesterday. I was in a little bit of a hole after qualifying, and I just didn’t do a good job. I had to dig out of that today. We had pretty good speed in our Fastenal Ford Mustang. I was pretty happy with it, and at times, had to move around the track quite a bit. I figured out Gateway really quickly. Not being able to run here last year, I felt a little behind getting going. Definitely found something there at the end. Honestly wish it was a 600-mile race because I felt like we could have kept getting better.”

Austin Cindric — Finished 13th: “Definitely frustrating having a speeding penalty … I’m a little frustrated with myself with that. You think something at the end of Stage 1 isn’t going to affect your race, but it just put us behind. We tried a bunch of strategy calls to get our Freightliner Ford Mustang up there. Had some good restarts at the end and made the most of it, I feel like. Those restarts got really scrappy. Proud of the team effort, proud of the recovery. Definitely a lot to clean up on my end to maximize what I thought was a Top-10 race car.”

AJ Allmendinger — Finished 14th: “We had an up-and-down day today fighting the balance in our No. 16 Chevy. I felt like we had a top-15 car most of the day, but we had to play defense to stay there. I wasn’t able to roll speed through the corner like I needed to be more aggressive and keep moving forward. We made a strategy call to take two tires, which didn’t work in our favor. Then we got caught up on pit road and restarted pretty far back at the beginning of the third stage. We’ll take a 14th- place finish after everything we battled with our car today and move forward to Sonoma.”

Justin Haley — Finished 16th: It was an up-and-down day for this No. 31 LeafFilter Gutter Protection team. We fired off tight in traffic, and it was just hard to pass. My crew chief, Trent Owens, made some really good strategy calls and we had positive adjustments all day, despite a couple pit-road mishaps. We had another good Chevrolet hot rod, and we will take a 16th-place finish after a hard fought day.

Ryan Preece — Finished 17th: “That was a really long day. I fought a tight race car all day long and every time we came down pit road, my guys made really strong adjustments. It just wasn’t enough to get us to the front and stay there. There were so many cautions there at the end, I was just trying to save the car. Overall, it wasn’t a terrible day for us after qualifying 29th. The fans were out in full force today, too, that was awesome to see. We’ve just got to keep grinding for better finishes.”

Erik Jones — Finished 18th: “Just an up-and-down day for the No. 43 Bommarito.com Chevy team. Didn’t end up how we wanted it to go, but we’ll go to work and get the car a bit better. I thought we had good speed, just didn’t have things go our way. We’ll work on it and hopefully go to Sonoma (Raceway) and have a solid day.”

Aric Almirola — Finished 19th: “We battled handing issues all day and just couldn’t find it. We were loose to start the day and it felt like our car was tight on aero and loose mechanically. Our long-run speed was really all we had today and we could pass cars late in the run, but we had so many cautions in the final stage we didn’t have the chance to run those cars down. Drew (Blickensderfer, crew chief) put me on offense on the last 20 laps with fresh tires and I thought we could’ve driven up to 15th, but someone missed a shift on the last restart and stacked us up and put us behind. Just one of those days. We had to battle to get all we could get.”

Ricky Stenhouse Jr. — Finished 32nd: “We kept our track position just like we wanted to. We got stage points, and I felt like we had a top-eight or so car, which was a big difference from last year. Obviously we’re striving to be better everywhere. We had a really good streak going of really good runs. It looked like the No. 2 (Austin Cindric) just, for some reason, right-reared the No. 3 (Austin Dillon) and took both of us Chevy guys out, so that’s a bummer. We definitely had a top-10 car today.”

Tyler Reddick — Finished 34th: “Our day kind of went bad early on, but our McDonald’s Camry was able to get through traffic pretty well, but as the track stated to cool off, it just started going away from us. It was starting to get frustrating out there for sure, to have a car that good, and it felt like it was just going away. I had a bad feeling that was coming soon. I was just getting ready to have to back off with how soft the brakes got, but I obviously should have been thinking about that a lap or two sooner.”

Carson Hocevar — Finished 36th: “I thought it was great. I had a blast. Just so thankful for the opportunity. I don’t have a job for next year. I know Al Niece and Cody Efaw wants me to run for them and I will forever run a race or however many. But man, I’m just so thankful that they gave me the opportunity – the opportunity to drive a Xfinity car and now driving a Cup car. I was running 16th.. just so surreal for the first time ever. I thought we were going to have a good day and be in a good spot for Schluter Systems, Celsius, Spire Motorsports, Ryan Sparks and the No. 7 Chevy team. Hopefully that call for a Cup ride isn’t the only one I get in my life.”

Cup results at WWT Raceway, driver points


Kyle Busch scored his third Cup victory of the season, winning Sunday’s Cup race at WWT Raceway in overtime.

Busch is tied with William Byron for most victories this season. Busch and Byron have combined to win three of the last six Cup points races (two by Busch and one by Byron).

MORE: Cup race results at WWT Raceway

MORE: Cup driver standings after WWT Raceway

Denny Hamlin finished second. Joey Logano placed third. Kyle Larson overcame struggles early in the race to finish fourth. Martin Truex Jr. completed the top five.

Corey LaJoie finished 21st, driving the No. 9 for the suspended Chase Elliott.

Ryan Blaney placed sixth and took the points lead from Ross Chastain, who placed 22nd. Chastain fell to fifth in the standings.