Dr. Diandra: Turn to turn experts for speed and passing


I always encourage fans to listen to driver-crew chief communications. I think you appreciate a race more when you understand a team’s strategy and struggles. A lot of the discussion focuses on the turns.

Drivers and crew chiefs break turns into at least three parts: entry, middle and exit. Some break the corners down even further, but let’s start simple.

Rule one: Grip is proportional to the force pushing down on the tire.

The total force pushing down on a car is the car’s weight plus the aerodynamic downforce. I’ll ignore aerodynamics to simplify the explanation.

That leaves just the car’s weight; however, the total weight isn’t the relevant factor. We’re interested in the weight pushing down on each tire. That’s why weighing a racecar doesn’t involve a giant car-sized scale, but rather four smaller scales, one for each tire.

In the absolute simplest case, equal weight pushes down on each tire. Each tire thus has the same grip.

Rule two: You can only go as fast as the least grippy tire.

Anyone who has driven on ice or snow knows this rule. If the rear tires of a rear-wheel-drive car are on an ice patch, the car won’t go. If one drive tire is on a slick surface, the car may move, but probably not the way you’d prefer it move.

That’s an extreme case, but you get the idea. The least-grippy tire limits a car’s speed. You can have lots of grip in your rear tires, but without grip in the front, you won’t be able to turn.

I’ve posited a perfectly balanced car, with the same force on all four tires. But even then, the forces are equal only when the car is sitting still.

Imagine yourself driving. You engage the brakes as you approach a stop sign. What happens?

Your body shifts slightly forward as the car stops.

So does some of your car.

Everything supported by a vehicle’s suspension (the chassis, body, engine, driver, etc.) can move relative to the wheels. Engineers refer to this as sprung mass because it’s attached to the wheels with flexible components like springs and shocks.

When you brake, the car’s sprung mass shifts from the rear toward the front. That means:

  • More force pushes down on the front wheels
  • Less force pushes down on the rear wheels.

Rule one tells us that the car now has more grip on its front wheels than its rear wheels. Rule two tells us that the car will be slower because, while the front wheels have more grip, the rear wheels have less grip. The rear wheels limit the car’s speed.

The opposite happens when you step on the gas. The sprung mass shifts from the front toward the back, and the car now has more rear grip than front grip.

Since a driver brakes coming into a turn and accelerates coming out of the turn, this shift in grip has a major effect on speed and handling.

And there’s more. There’s also load transfer when a car turns. You’ve no doubt seen the tippy truck sign, right?The highway sign showing load transfer

A truck turning left could tip because of how its sprung mass shifts. Intuition might suggest that the truck should tip in the direction it’s turning, but that’s not how it works. In a left turn, load transfers from the left wheels to the right wheels.

And if you’re performing some combination of turning and braking or accelerating, load transfer happens in all directions.

Rule three: All the effects of load transfer add up.

Let’s combine all three of the phenomena to understand what happens when a driver turns a racecar.

  • She brakes as she approaches the turn.
  • While still braking, she starts to turn.
  • The car rolls through the corner at constant speed, with all the load transfer from left to right having taken place.
  • She accelerates as she starts to complete the turn.
  • As she leaves the turn, she accelerates while going straight.

The table below summarizes how the loading of the wheels changes during this process.

A table showing how the load changes as a car turns

The magnitude of the shift in force on the tires is proportional to the height of the car’s center of gravity. Semis and SUVs have a high center of gravity. That’s why they’re more likely to tip on a turn than a low-to-the-ground sports car.

One of the Car of Tomorrow’s vexing points was that its center of gravity was quite high for a race car. That made load transfer a much bigger effect. The video below shows the then-brand-new Car of Tomorrow at Martinsville Speedway. You can see as Robby Gordon comes out of the turn and gets on the gas that there isn’t even enough force on the left-front tire to keep it on the ground.

A video showing how significant load transfer can be

Because teams have access to detailed data about how their drivers — and all the other drivers  — navigate corners, they can analyze a turn in exquisite detail. That’s why they don’t stop at entry, middle, exit, but specialize to late entry or early exit, for example.

William Byron’s crew chief Rudy Fugle explained how teams use this data on NASCAR America Motormouths.

“We break the track down into segments,” Fugle said, “and say, entry, early entry, middle… wherever, these parts of the corner make the lap time. All the fast cars that are making laps make it here.”

Making a fast lap is important for qualifying, but there’s more to racing than speed. You have to be able to pass other cars, and that frequently happens in the turns as well.

“And then we also have some analysis on the most passes are made in this part of the corner,” Fugle said. “So you kind of know, like, OK, to go fast I need to be good here and to make passes, I need to be good here, because sometimes they’re in different spots.”

The challenge of dealing with a car whose grip constantly changes is, in my opinion, one of the most underappreciated aspects of racing.

When I lived in Nebraska, I put bags of sand in my pickup truck’s bed to increase its rear grip. That additional force made the truck less likely to get loose. Racing is like having a bag of sand on each corner of the car, but the weight of each sandbag changes when you speed up, slow down or turn. The best drivers are those with an expert feel for how far they can push their car without exceeding its traction limit.

NASCAR Power Rankings: William Byron, Kyle Busch rank 1-2


Kyle Busch moved closer to the top spot after his win Sunday at WWT Raceway, but William Byron keeps hold of No. 1 after another top-10 run.

The series heads to Sonoma Raceway this weekend, the second race of the season on a road course.


(Previous ranking in parenthesis)

1. William Byron (1) — He goes into Sonoma with six consecutive top-10 finishes after his eighth-place result at WWT Raceway. Byron has led a series-high 717 laps this season.

2. Kyle Busch (4) — Recorded his third win of the season Sunday. He is tied with Byron for most wins this year. Busch scored 59 of a maximum 60 points and won his first stage of the year Sunday. He has 16 playoff points. Only Byron has more with 17 this season.

3. Kyle Larson (3) — His fourth-place finish continued his up-and-down season. In the last nine races, Larson has two wins, four top fives, a 20th-place result and four finishes of 30th or worse. He has led 588 laps this season, which ranks second this year to Byron.

4. Martin Truex Jr. (2) — His fifth-place finish is his sixth top 10 in the last eight races. He ranks third in laps led this year with 383.

5. Denny Hamlin (7) — Runner-up result at WWT Raceway is his fourth top 10 in the last seven races.

6. Ryan Blaney (10) — Followed Coca-Cola 600 win with a sixth-place run at WWT Raceway. He had an average running position of 2.6 on Sunday, second only to winner Kyle Busch’s average running position of 1.9.

7. Joey Logano (9) — Third-place finish is his second top 10 in the last four races.

8. Kevin Harvick (NR) — His 10th-place finish is his fourth consecutive finish of 11th or better.

9. Ross Chastain (6) — Lost the points lead after placing 22nd, his third consecutive finish outside the top 20.

10. Ricky Stenhouse Jr. (NR) — Headed for his eighth top 15 in a row until he was collected in a crash after the contact between Austin Cindric and Austin Dillon late in Sunday’s race.

Dropped out: Chase Elliott (5th), Tyler Reddick (8th)

NASCAR will not penalize Austin Cindric for incident with Austin Dillon


Despite Richard Childress and Austin Dillon saying that Austin Cindric intentionally wrecked Dillon late in Sunday’s Cup race at WWT Raceway, NASCAR will not penalize Cindric.

Elton Sawyer, NASCAR senior vice president of competition, said Tuesday on SiriusXM NASCAR Radio that there would be no penalty to Cindric after reviewing the contact.

Dillon and Childress were upset about the incident, which brought out the caution on Lap 220 of the 243-lap race. Dillon said NASCAR should suspend Cindric for the contact, just as NASCAR suspended Chase Elliott one race for hooking Denny Hamlin in the Coca-Cola 600.

Contact between the left front of Cindric’s car and the right rear of Dillon’s car sent Dillon up the track into Ricky Stenhouse Jr. Dillon finished 31st. Cindric continued and placed 13th.

Dillon told Frontstretch.com: “I was wrecked intentionally by (Cindric), hooked right just like Chase and Denny and Bubba’s deal (in wrecking Kyle Larson at Las Vegas in 2022). He better be suspended next week.”

Childress said: “(Dillon) had drove up to about 10th until (Cindric) wrecked him in there on purpose, sort of a payback.”

Sawyer said a review of the incident included viewing video and data.

“We didn’t see anything — and haven’t seen anything — that really would rise to a level that would be a suspension or a penalty,” Sawyer said. “It looked like hard racing. One car coming up a little bit and another car going down.

“As we said last week, we take these incidents very serious when we see cars that are turned head-on into another car or head-on into the wall. I spent a lot of time (Monday) looking at that, looking at all the data, looking at TV footage and just deemed this one really hard racing.”

Sawyer said NASCAR plans to talk to both Cindric and Dillon “to make sure we’re all in a good place as we move forward to Sonoma.”



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.

The ARCA Menards Series West also is competing this weekend at Sonoma Raceway. Cup driver Ryan Preece is entered in that event. Xfinity drivers Cole Custer, Riley Herbst, Sammy Smith and Parker Retzlaff also are entered in that race, which will be held at 6:30 p.m. ET Friday.


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.