Indy Is Not Just Four Boring Left Turns

The Indianapolis Motor Speedway might look like four identical left hand corners. That's not even close. It's so much more, and that's what makes the Indy 500 such a challenge.

DW Burnett/Puppyknuckles

Thirty-three men and women, going in circles for 500 miles on Sunday at the Indianapolis Motor Speedway. How hard could it be?

“Wind matters, [ambient] temperature matters, track temperature matters. This [track] is its own thing,” says Danica Patrick, who qualified seventh for her farewell Indy 500.

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The new reality for Patrick and her rivals at the 2018 edition of the Greatest Spectacle In Racing involves fast hands.

They’ll be needed to keep their 235mph bullets from spinning and clouting the wall while running in a pack of cars. It’s a big change from last year’s Indy 500 where custom bodywork made by Chevy and Honda gave drivers the ability to race for hours without concern as they were blessed with cornering stability through ample aerodynamic downforce.

Those comfy days of 2017 are all but forgotten after a harrowing week of practice and qualifying for America’s defining motor race has revealed a downforce shortage with the curvy new 2018 bodywork created by IndyCar.

In the simplest terms, the finest drivers have been pushed to their limits while attempting to remain in control of their cars, and as the field of 33 have reported, circulating in a long train of cars is a nightmarish scenario for all but the leader and the next driver or two in their wake. For those stuck fourth, fifth, or further behind in a snake-like procession, the aerodynamic turbulence makes for frightening moments.

With insufficient air flowing over their front wings, cars deeper in a pack have understeered towards the wall, then regained grip and produced oversteer. All while traveling the length of a football field per second. Mix in the variables brought by Mother Nature and how a hot day results in thinner air, which takes away even more precious downforce, and Sunday’s race—projected to be 90 degrees—is primed to be one of the toughest Indy 500s to complete in decades.

Even running solo outside of a pack, as James Hinchcliffe described on his visit earlier in the week to Road & Track, has its stability challenges.

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“What’s so cool about Indy is, obviously the track is so big, and so fast, it’s so affected by weather,” says the Canadian star who missed making the cut in qualifying. “Wind and track temp, especially. On a given day, the answer to that question changes depending on what the weather conditions are. For the sake of argument, let’s say you have a tailwind into Turn 1. What that means for us is the car’s going to be really unstable turning in to the first corner, you’re going to have to protect the rear on entry, but you’re also going to be dealing with understeer on exit. You’re going to work your tools (anti-roll bar adjusters, and a hydraulic cross weight jacker) a little bit, change your line a little bit to adjust for that.

“That also means you have a bit of a crosswind as you turn into [Turn] 2, and then as you exit 2 you’re going in to a full-on headwind. So, somewhere in the middle of two the nose of that car is just gonna get pinned down and it’s gonna get really, really loose mid-to-exit.”

Although the 2.5-mile Indianapolis Motor Speedway oval is meticulously maintained, freezing winters in Indiana introduce new surface imperfections each year.

“There’s little bumps on the exit of two as well that sometimes throw you off and you need to be cautious of,” Hinchcliffe added. “Then you go and turn into 3 in a full headwind, so you’re super high on center pressure, the front wing’s doing a lot of work, the nose is very on the ground, very pointy. You have to be very careful with your hands going in, again you’re adjusting tools based on that. There’s some bumps in the middle of 3 that can throw the car off.

“Into 4, the wind direction is going back that way, it makes the car understeer quite a bit because it’s essentially disrupting the flow of air across the front of the wings, rather than air just coming at it, a bunch of air is thrown at it from the side and you actually lose a bunch of front grip there. If you have a tailwind into one, that’s what you have to do. If it’s any other direction, all that changes. You have to know how to do all these things in every given condition because at some point during the race the wind could change, get stronger, weaker. Part of the reason why you need so many days of practice is to get sort of a database as to what to do in a given condition.”

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With help from our friends at Andretti Autosport and Team Penske, a rare look at some of the numbers and graphs teams gather from their private on-board computer systems bring some of what Patrick and Hinchcliffe have mentioned to light.

Shifting the conversation strictly to the busy hands that will be spinning steering wheels left and right with while fighting unwieldy chassis behavior in traffic, Andretti technical director Eric Bretzman assembled a few visuals to tell the tale.

Taken from a lap spent behind a group of cars, one of his Honda-powered drivers dealt with aerodynamic wash—taking away stability from the front wings—which forced a change of line through the corners to keep from making .

To start, using the entry of Turn 2 as a reference point for managing understeer and turbulence onto the long back straight, data channels reveal the driver is experiencing 3.94 lateral Gs as he returns to full throttle and accelerates from 219.5mph following big lifts on the throttle to keep the nose of the car from sailing towards the wall.

One of Andretti Autosport’s internal data sheets.
Andretti Autosport
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Backing up a little bit on track to just prior to turning in, Bretzman highlighted the section below and explains how running in traffic leads to a harrowing moment in time as Turn 2 beckons.

“Turn 2’s entry is a bit of a point of interest as we’ve seen several cars ,” he said. “Turn 2 is open to a significant amount of wind effect but zooming in on the vertical acceleration (below) shows a 250-foot section of track seemingly falling away from the car and road wheels. The effect is similar in the other corners but the event occurs in less distance entering the other three corners.

“Here you see lateral acceleration (purple) decay and the driver is backing steering wheel (black) out as the rear tires begin to slide and then the whole car slides. To keep the car on line and not drift into the wake of the car in front, the driver then breathes the throttle to hold his trajectory and limit the slide.”

Andretti Autosport
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Bretzman added another layer to the complexity involved with successfully completing a lap in the Indy 500.

Bretzman’s notated corner map
Andretti Autosport/Eric Bretzman

Considering there’s 200 laps to navigate in the race, the notion of “four boring corners” per lap is forgotten. As Team Penske noted, drivers can look forward to spending almost a quarter of each lap—somewhere in the nine- to 12-second range—above 3gs

Multiplied times 200 laps, it equates to 30-40 minutes of having one’s internal organs mashed to the right. Keeping both eyes affixed well down the track or around the oncoming corner, while chasing a train of cars of trying pass/fighting to avoid being passed, with a squirrely car shifting from oversteer to understeer…at average lap speeds above 220mph…

It’s anything but simple.

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