Note: This is a continuing series for INDYCAR.com, with different guests, leading into each race weekend for the NTT INDYCAR SERIES, focusing on various technical challenges of each respective circuit.
The fifth round of the 2023 season for the NTT INDYCAR SERIES stays home and officially kicks off the Month of May festivities with the GMR Grand Prix on the Indianapolis Motor Speedway road course.
The 2.439-mile, 14-turn (five left, nine right) road course includes a section of the superspeedway oval, with competitors going clockwise down 2,869 feet of the front straight before hitting the rest of the interior circuit. The track remains relatively flat throughout, with up to 9 degrees of banking making up a small portion of the layout.
A unique two-day event features two practice sessions and an NTT P1 Award qualifying bout Friday, ahead of Saturday’s morning warmup followed by the 85-lap (207.315 miles) race set to have the green flag wave at 3:30 p.m. ET (NBC, Peacock, INDYCAR LIVE and the INDYCAR Radio Network). The qualifying record is held by Will Power, who stormed to a flying lap of 1 minute, 7.7044 seconds (129.687 mph) in 2017.
This week’s featured guest is Garrett Mothersead, race engineer for Simon Pagenaud’s No. 60 AutoNation/SiriusXM Honda fielded by Meyer Shank Racing. Mothersead helped guide the Frenchman to a runner-up result in last year’s rain-affected contest.
Q: What is it like preparing for the IMS road course for the GMR Grand Prix weekend to kick off the Month of May?
Garrett Mothersead (photo, right): Well, it's pretty different because you also have the workload of the Indy 500 that comes right after it. So, it's a little bit different in the fact that you probably do stuff further ahead than you would for a normal race weekend, just because you have so much new stuff coming out for the "500" that you're probably looking back and forth at during the week you're prepping for the Indy road course. It's a little bit different prep in terms of that, but the May race is generally cooler. And the Indy road course is unique in that it's a track that we go to twice a year, so we get to see the track in two very different conditions. The spring race, the tire degradation isn't as bad, and I think it's actually a fun race. I like it because you can actually race very hard there the whole stint, and you don't have to worry about it as much. Also, as you saw last year, the weather is definitely something that impacts the spring race more. Indiana in the spring, you can get anything. Like last year, having a rain race, that made it a totally different challenge that kind of flips everything on its ear and it becomes a much different kind of race, which is interesting. It makes it fun.
Q: From a general engineering point of view, what type of setup do you lean toward at a place like the Indianapolis road course and how does that relate to maybe other tracks of that style where it's a non-elevated, flat road course?
Mothersead: There's a couple of unique things about the Indy road course. One of the big things is the lap time is dominated by straight-line speed and braking, probably more so than most of the other road courses we go to. You have to have fundamentally a car that's very stable under braking and you play a compromise between that quality and having the balance that the driver wants in terms of other corners, and it's pretty unique in that situation. As for being a flat track, it creates opportunities for you to be a little more aggressive in your setup than you would be at a place like a Barber (Motorsports Park) or a Mid-Ohio (Sports Car Course). And certainly, the spring race leads to that more than the summer race, where you have to back things off a little bit.
Q: With it being a relatively smooth track, at least from the optics point of view, I'm going to guess it's probably favorable to keep ride heights lower, and it's one of those layouts you don't have to worry about really softening up the suspension or the dampers quite like you would a street course?
Mothersead: Yeah. Although in saying that that's not 100 percent true. We've had some fairly successful setups that vary greatly in terms of stiffness. It's more paying attention to the fundamentals in terms of your ride heights and making sure that you have your aero sorted on how you're making your downforce. That is where it actually comes down to really being important and being a smooth track. It does become more of an aero-dependent track, and you can be more aggressive with that stuff.
Q: You talk about how aggressive you can be with straight-line speed and braking. I’m going to guess that you are really pushing the mark with a top-gear type of setup, too, of trying to make sure your setup is more built for that straight-line speed?
Mothersead: Yeah, we spend quite a bit of time there. Of course, Indy, at that time of the year, the winds are pretty variable and when you get a north-south wind during the weekend, it leads to a lot of hours going through and trying to sort out exactly where the optimal gearing is.
Q: How tricky is it to find that balance, though? Is it more mechanical vs aerodynamic grip because you’re on a flat track?
Mothersead: Well, it's actually a balance between the two because the circuit carries a number of kinds of things. Turn 14 and Turn 4, both of those are highly dependent on aero grip, and, of course, most of your braking is dominated by aero grip, so you have to pay attention to that but also try and sort out the mechanical grip. The mechanical grip probably comes more, at least it sticks its head out more in the summer. In the spring race, generally with the cooler temperatures you can get away with a little bit more and you can be a little more favored toward the aero side than mechanical grip side.
Q: The corners you just listed, would you say those are probably the trickiest parts of the track to get right from a setup point of view or is there another trouble spot that you isolate toward?
Mothersead: Oh, there's, there's a number of trouble spots there. Braking for Turn 7, which is the end of the back straight, that's always a big thing. Running through Turn 7 to Turn 10, that set of chicanes, that is always a pretty big key for lap time. There's a lot available there if you can get it just right, but Turn 14 usually gets the driver's attention in the race, especially as you get on worn tires, they'll be very verbal about they don't like where it is.
Q: I'm about to ask something that might be a stupid question; from a setup point of view whenever you're going from road course to oval and the fact that it is IMS, even though you're running on the road course not the oval and going completely the opposite direction, is there anything that's transferrable?
Mothersead: There are a lot of things that we've learned over the years from superspeedway stuff going all the way back to IRL classic when we were just running ovals. There are a lot of lessons that were learned there that have carried over into the road course package, and they've become more important at some places like Indy road course or Road America. We do pay attention to those things. With as tight as things are, man, you can't give up anything.
Q: We run here twice, once in spring and once in summer, like you talked about earlier. Do you find a situation where because there's more tire degradation for the summer race than the spring race, is the setup drastically different because maybe humidity/air thickness or what have you, does it honestly kind of in some ways require a drastically different setup or one that needs quite a bit of just different subtleties?
Mothersead: I think it's more just different subtleties. When we come back in the summer, you have very limited amount of track time, so you don't have a lot of time to just develop something totally different and to really work with it and to know where you're going to be. So, you have to stay kind of close to home, and that holds true for a lot of the tracks now with the limited amount of track time. You don't have time to do something revolutionarily different, so it comes down to more a lot of subtleties that you do just to try and help yourself and take care of it and add drive ability to the car.
Q: Does the IMS road course get grippier as the weekend goes on?
Mothersead: It does grip up quite a bit. The effects on lap time aren't as dramatic as you'd have on a pure natural terrain road course, like a Mid-Ohio, because you have a lot of corners where as you add grip, the lap time just shoots up. Indy road course doesn't quite do that, but it does rubber in quite a bit, and it doesn't reset much. It really doesn't. In the summer race, you have some of the other rubber from other series that's not quite as good as ours. That gets in the way. But in the spring race, it's a pretty continual climb all through the weekend. I don't think you really hit peak grip until you're about halfway through the race.
Q: Really?
Mothersead: Yeah, but there is a drastic change as you go through the weekend. By the time you get to qualifying, you certainly know you have a way different track, and we kind of have to follow that progression with the car.
Q: Each driver has a different style of preferred feel in setup; some would rather have more understeer and others oversteer, or even a neutral balance. Simon Pagenaud is great at a hell of a lot of tracks and he's very, very much a technical driver, but what have you seen that just seems to fit why the IMS road course layout and him mesh so well?
Mothersead: Well, I think you kind of touched on it. He is a technical driver, and he thinks a lot about what he's doing and how he's doing it in terms of his preferred balance. He's a little bit more toward an understeer-type driver, but that is not a strict rule. He's adaptable in terms of it, and he understands that certain tracks require this, and certain tracks require that. So, I don't think he's really (devoted) to balance one way or another. He does like having a very stable rear, something that allows him to attack. That's kind of his style, and I think Indy road course just opens itself up to that kind of thing. The fact that being aggressive in the brake zones, being aggressive how you approach corners, it rewards you. And I think that's probably why he's good there, but it's a thoughtful aggressiveness.