Race Weekend Central

Tech Talk: Aerodynamics & Big Guys Sitting on a Window with Mike Wheeler

As the dog days of summer approach, the schedule has a switch this season with Chicagoland Speedway moving to the week before Daytona International Speedway in the Monster Energy NASCAR Cup Series. The teams will have to deal with different weather and a new tire in addition to the rules changes for 2018. The aged surface at Chicagoland Speedway doesn’t have many bumps, but there are some that have to be taken into consideration.

This week, crew chief Mike Wheeler revisits his strategy with driver Denny Hamlin to win a playoff point vs. going for the win, along with the reduced number of cautions and off-track incidents at Sonoma Raceway. He then looks to Chicagoland and the aero challenges of the character of the track, sideforce vs. downforce and underbody aerodynamics — plus much more.

Mike Neff – At Sonoma, you grabbed a stage win, but you had a very hard time getting back to the front over the final stage. Was track position really that critical out there?

Mike Wheeler – Yeah, passing at Sonoma is hard enough. There are only two or three turns where you can really set someone up to pass. Getting the stage win was a goal. We knew we weren’t quite as fast as the top two guys. We didn’t think we would get five stage points, so we took the one point we could get. Ultimately, we restarted back around 20th for the last stage, and it took a long time to get back up there, but [I’m] happy that we got a top 10 out of it.

Neff – Is it a matter of the cars being that much better so the drivers can keep them under more control, or are guys racing more conservatively than they used to?

Wheeler – I think the durability of the cars has gotten better and better. It is something we’ve worked hard on in the last five-to-10 years, to make sure that we don’t have mechanical problems. I’m sure that is the case for a lot of teams.

Equally, I think all of the drivers have gotten better and better, as far as being drivers themselves on the road courses, staying between the lines and not getting out of shape. As much as they’re racing pretty aggressively, I think everybody knows their boundaries a little bit better compared to where they were five or 10 years ago. Ultimately, you get a lot of green-flag runs, which isn’t bad racing, it’s just different racing. I think it is a combination of drivers and equipment.

Neff – Going forward, is there much of anything that transfers from the cars that ran at Sonoma to Watkins Glen International or the roval at Charlotte Motor Speedway?

Wheeler – There are a few things you can carry over. A lot of your steering stuff, driver-feel stuff, obviously relays. Braking packages and that kind of stuff is very similar. Gear ratios, not so much, with the difference in speeds. Springs and balance is different because of the different tires. Getting the driver to feel right and see right [and] getting his brakes happy applies to the other tracks we go to.

Neff – Next up is Chicago, and you have to feel confident heading there considering your driver has four consecutive top 10s and a win there in the last three years. How similar do you think your car will be compared to your recent trips there?

Wheeler – Ultimately, we’re racing at a different time of the year, so that is a question mark in our book. The rule changes over the winter have been a factor over last fall compared to this summer. We’ll also have a tire change coming up this week, so those are three contributing factors that will make it different. It is still the same racetrack, and that is something that you can’t forget about. It will have a lot of the same characteristics, and if the driver has a good feel for it, he can hopefully get back to the feeling and get back to running top fives or top 10.

Neff – The bit of a curve to the backstretch is unique. In terms of intermediates, what track is Chicagoland most similar to in setup?

Wheeler – It was almost like the old Texas [Motor Speedway] and Charlotte, without as much banking. It was a run-of-the-mill, average intermediate. It was medium-banked, not heavy banking like Charlotte or Texas, but more banking than what Kansas [Speedway] has. It is kind of like Homestead [-Miami Speedway] a little bit, where you can move around a little bit. Homestead has moved up to the wall quite a bit, while Chicago is back and forth. It has enough roughness so there are some characteristics that you have to work around. There are different lines that you can run while tire falloff is somewhat of a concern. It is very much a nice, average, intermediate track.

Neff – Maintaining the platform is what you guys always talk about, but driver comfort has to be somewhat of a concern. How much do you have to accommodate Hamlin’s comfort in the car vs. keeping a platform as down to the earth as you possibly can?

Wheeler – Definitely want to keep the attitude of the car as appropriate as we can. The bumps at Chicago aren’t too rough to where you can’t keep both things happy. Obviously, you can get more aggressive in one area over the other. If you skip over the bumps a little bit too much and get out of shape, that is something you definitely have to keep aware of. There are other tracks we go to like Michigan [International Speedway] where the bumps aren’t a problem at all. Chicago is one of those tracks where you might get a little too aggressive on platform and hurt yourself over the bumps or you might try and take the bumps a little better and screw up your platform.

Neff – How important is the sideforce on these cars for maintaining control and providing more speed?

Wheeler – Aero balance in terms of downforce vs. sideforce is something you have to be aware of. The right side of the cars are shaped accordingly with a little bit of tail offset and all of that kind of stuff. The car is in a little bit of yaw. NASCAR gives us a little bit of tolerance there but not a whole lot compared to what we used to run. Five or 10 years ago, we had almost an extra degree of yaw. Between tire slips and other things, you do get some amount of sideforce that you can play with. That makes it a little hairier in traffic than what you really desire, but ultimately it is something that you try to optimize and maximize. It isn’t something you can really play with that much like a nice, sweeping corner. All you can do is try and maximize what you have in your car and then adjust the balance with other things.

Neff – How much are you still focusing on getting the air to move efficiently underneath the car with the new splitter pan and other changes?

Wheeler – Underbody aero is one of those things you do or chase. It seems less sensitive this year than in past years with the splitter update and other things. Obviously, any kind of aerodynamic gains we can get, we chase. At the same point last year, we had a pretty shaped splitter on the car which contributed to some underbody airflow. This year is definitely different. As much as I like to say we’re always making improvements in areas, sometimes the rule changes make you work in different areas.

Neff – Joe Gibbs Racing had some issues a little bit back in inspection concerning wear on the splitters. Was it a materials issue that caused NASCAR concern, or was it more of a setup issue?

Wheeler – I would say it was more of a setup issue with how hard we were hitting the racetrack than anything else. It wasn’t anything egregious on our part as far as doing anything. At the same time, when NASCAR saw how we were cleaning up the splitters to get ready for tech, they weren’t happy with it and wanted us to change them out, so we did.

I don’t think there was anything really that bad on anyone’s part. When you surprise NASCAR with something they haven’t seen before, they can get defensive sometimes. I understand their case, and I thought it was all good. They wanted us to work on it a little more than I thought we should have to, but that is just part of the sport.

Neff – We have seen some teams have issues with the back windows on their cars caving in and the supports failing that held up that section of the window. Is that something that caused you to add an additional support in that location or change the way the supports were being constructed to help that window maintain its shape?

Wheeler – Yeah, we definitely had to work on it at a few tracks with the aero loads a lot higher. Chicago is not one of those tracks that you have to worry about that as much as others. Michigan was the biggest one we’ve had so far. California [Auto Club Speedway] is up there as well. By the time you go to Michigan, you’re talking about 40 percent more load in the rear window than you have at one of the average intermediates. You are going 215 mph into the corner at Michigan, while at some of these intermediate tracks it is 180 or 190 [mph]. It doesn’t sound like a whole lot in terms of mph, but the aero load is magnified for every mph you go over that. We definitely had to do some extra work at Michigan, but I don’t see it being that much of a concern at Chicago this week.

Neff – Does it say something about how efficiently you are getting the air to flow over the car that you’re getting that much aero load on the back window of the car?

Wheeler – A little bit. The whole car itself makes a lot of downforce. Obviously, with the speeds we’re going, you’re talking about having a person standing on the back window for the amount of aero load that it is holding up. You think pushing on it by hand would give you a feel for what is going on. Honestly, you have a pretty heavy guy sitting on the back window for the amount of load that is on the back window at some of these tracks. As much as we say we are trying to get all of the aero, we can get honestly a lot of it has to do with weight, too. We could make the brackets out of solid steel and as beefy as possible, but that would affect our CG (center of gravity) and some of our nose weight adjustability, and we don’t want to that either.

Neff – How far off of the ground are the cars’ centers of gravity?

Wheeler – Without getting into too much detail, all of these cars are around 15.5 to 16 inches for CG. You can run the car lower, trim your side skits and get the dynamic CG even lower than that. Depending on your brake system and some of the other subsystems in the car, or a superspeedway car vs. short track car, even the tires, it can vary a decent amount. You don’t ever purposely build a car with the CG intentionally higher, but sometimes with some of the subsystems you want to use to get the car to maintain the state you want does raise the CG up some. CG is like aero, you always want to get everything you can as far as making the car faster. Any time you lower the CG, it is never a bad thing.

About the author

What is it that Mike Neff doesn’t do? The writer, radio contributor and racetrack announcer coordinates the site’s local short track coverage, hitting up Saturday Night Specials across the country while tracking the sport’s future racing stars. The writer for our signature Cup post-race column, Thinkin’ Out Loud (Mondays) also sits down with Cup crew chiefs to talk shop every Friday with Tech Talk. Mike announces several shows each year for the Good Guys Rod and Custom Association. He also pops up everywhere from PRN Pit Reporters and the Press Box with Alan Smothers to SIRIUS XM Radio. He has announced at tracks all over the Southeast, starting at Millbridge Speedway. He's also announced at East Lincoln Speedway, Concord Speedway, Tri-County Speedway, Caraway Speedway, and Charlotte Motor Speedway.

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