Why Jeff Gordon is Jealous of Carl Edwards’ Yaw

Apparently, Jeff Gordon has a slight case of yaw envy. David Newton reports on ESPN.com that Gordon asked NASCAR to take a look at the No. 99 car of Carl Edwards because he thinks that yaw is the reason Carl’s been so competitive this season.

You may have learned that it takes three numbers to uniquely locate an object in space: For example, right now I’m in Los Angeles at the corner of Hope and 8th Streets and I’m on the 11th floor.

The limitation of this description is that it only identifies a point. I (like a car) have spatial extent. I could be lying down or standing up, and the three points I just specified don’t tell you anything about how I’m oriented, only where I’m located. We have to specify the angles the car makes with respect to three axes, which we call the x-axis, y-axis and z-axis. In vehicle dynamics, the x axis is along the length of the car, the y-azis is crosswise, pointing toward the driver’s right, and the z axis points downward, as I’ve drawn below. (Engineers take the z-axis to be positive in the downward direction.)

Yaw describes the rotation of the car about the z-axis. The yaw angle is the angle between a line pointing in the direction the car is moving and the car’s x-axis (which is the direction the car is pointed). In the simplest case (shown on the left side of the drawing below), the car is traveling straight and is pointed in exactly the same direction it is traveling, so it has no yaw. The car on the right is yawed, which means that the car is headed in a different direction than it is pointing.

A car by definition is yawed when it corners because it is pointing in a different direction than it is moving at every point along the turn. Yaw is important because air hits the car differently when the car is at an angle to the oncoming air compared to when it is hitting the air head on, as shown below. In effect, the car on the right has a head start on the turn because it is yawed before it enters the turn. Yaw puts the car in a position so that the air helps the car turn.

A number of people have noticed that some cars seem look yawed heading down the straightaway. They appear to have an inherent yaw built into them. Darlington has nice straightaways, which is why yaw has been in the news this week.

Let’s review some history. The old cars were asymmetric–literally kidney-bean shaped–as shown below. Compare how much of the left fender (on the right side of the picture) you can see relative to the right fender. Gary Nelson, the founding director of the NASCAR Research and Development Center said once that the cars were so misshaped that they looked like they had been in an accident before they even got on the track.

All of this body manipulation was for aerodynamic advantage; however, the research that goes into figuring out exactly how to optimize bodies, as well as the cost of cutting off and replacing bodies, was getting out of hand. This was one NASCAR’s major motivations in introducing the new car.

Compare the old car with the new car in the drawing showing yaw. There still is some built-in asymmetry in the new car: Note how the wing isn’t exactly centered between the two taillight decals, for example. The left rear quarter panel is much more tapered than the right rear quarter panel; however, the amount of asymmetry is pretty much fixed by the NASCAR body templates.

Of all the drivers, Jeff Gordon knows that you don’t mess with the new car’s body. He has complained that something is more amiss than it should be with the rear end gear on the No. 99, causing it to have yaw and thus giving it the same type of asymmetry the new car’s fixed body shape was meant to eliminate.

NASCAR cars have a solid rear axle. The rear end gear links the driveshaft to the rear wheels. There are three holes in the rear windshield: Two of those are for adjusting the springs on either side of the car. The third (the bottom one on the right) is for adjusting the trackbar. The trackbar shifts the rear end gear to the left or the right, as I’ve illustrated in the drawing below. I’ve exaggerated the shifts–if I drew them to scale, you wouldn’t be able to see them. The leftmost drawing is a car with no offset in the rear end gear. Note how the front and rear wheels are lined up. The rear wheels would follow right in the front wheels’ tracks. The middle drawing shows a car with the rear end gear shifted to the right and the rightmost picture shows that a car with such a shift will be yawed.

Kyle Busch referred to the way Edwards’ car moves as it looks “stupid going down the straightaway because it’s dog-tracking.” (ESPN). A running dog is usually a little sideways. The rear paws never follow in the front paw prints. It’s also sometimes called crabbing, and refers to the situation shown above: the rear wheels do not follow straight behind the front ones.

The situation with some cars is so extreme, that Gordon said:

“When cars can’t even get on the scales because they’re running sideways, it’s something they need to address.” (ESPN)

The scales used during inspection are four plates(two in front, two in the rear), that are in line with each other. Jeff is suggesting that the offset between the front and the rear wheels is so great that some cars have trouble getting onto the scales.

It’s ironic that Gordon is complaining about this, as Hendrick Motorsports was one of the first teams to experiment with introducing yaw using the suspension. One possible motivation for Gordon’s comments is that he is of the opinion that Roush Fenway Racing is headed down the same slippery slope as coil binding: The engineers are modifying the car in way that makes it much more difficult to drive.

Almost every team has tried to duplicate what Edwards has, but not every driver can handle it. “It makes the cars drive so terrible that it doesn’t really help us in any way that we really need it,” Gordon said. (ESPN)

There are rules about how much you can move the trackbar, so there are obviously other things being done to induce yaw in the car. One possibility: The wheelbase (the distance between the front and rear wheels) can be 110″ plus or minus 1/2″. If you make the wheelbase 109.5″ on the left side and 110.5″ on the right side, you’ve gained an inch of asymmetry. There are a number of other places where you can make little changes and, when all the little changes are considered, they add up to a significant effect.

I noted early on in the introduction of the new car that it was only a matter of time before the very clever people working at race shops would come up with ways to get around the new NASCAR-imposed limitations. One consequence of this type of offset is that the cars are drifting, much like they do on dirt tracks. It should be no surprise then, that someone like Edwards, who still does a lot of dirt track racing, is comfortable driving a car set up like this. That’s one rationale to account for why Edwards, who really struggled with the new car last year, is doing so well this year. As with coil binding, some teams have figured out how to get yaw and others are a little behind on the curve. Some drivers caught on to how to drive a coil-bound car a lot faster than others. The question that remains is whether there are other ways to get the car to turn better that would be more comfortable for the drivers who aren’t comfortable driving horizontally down the straightaways.

19 Comments

  1. Only….ONLY…Jeff Gordon would whine about Carl Edwards….this is the same Jeff Gordon who asked Martinsville / NASCAR officials for permission to work on his damaged vehicle (only his vehicle) during the red flag repair at the speedway last year….remember Jeff…let’s keep the playing field level…or all’s fair as long as the Hendricks entourage leads the way….but let’s not let the “dreaded” Roushketeers make improvements which would allow them to run with the predetermined “Hendricks dream team.”

  2. I remember some of the first instances of ‘yaw’ being mentioned by a driver. And that was Ryan Newman’s rookie season in the early 2000s. But then again, he has an engineering degree!

  3. jeff gordon jealous of carl edwards HAHAHA i needed a good laugh.81 wins 4 cup titles compared to what 5-6 wins in 3-4 years wow that’s something to be jealous about.had it been somebody else that answered this question nobody would make a big deal out of it but let jeff gordon say something then he is either whinning or jealous of somebody else. IF YOU DON’T LIKE THE ANSWER DON’T ASK THE QUESTION…

  4. I also thought it was strange for Gordon to be complaining about this, since there’s no reason why HMS can’t do the exact same thing (provided they know exactly what RFR is doing). I suspect (and it’s hard to tell because we get sound bites filtered through the media) that Gordon is more concerned that the new car is going to go the same way the old car went, which is to say that teams are going to come up with more and more tricks that to subvert the intent of the rules without violating the letter of the law. That is my suspicion, but not having been there, I can’t say that’s the case. I believe that the reason the media even mentioned Gordon’s remarks is because he does have a reputation for speaking out about the sport as a whole.

  5. I really got a laught,out of jeff gordon being jealous of carl edwards?how many races and championships has jeff won? The only thing I see is he will have to make a fool of himself doing the back flip.give me a break!!!!!

  6. whining wonderboy again
    a little cheese
    now that the cars are equally prepared the hendrick boys arent/wont dominate anymore..no more trickery, etc….
    guys like mark martin and jr. who are the best will rise to the top in equally prepared card..
    If you dont like the answer, dont ask the question ,LOL

  7. Great explanation!

    But I wonder if this “yaw” set-up doesn’t cause hot spots in the tires (especially the right front), which can lead to unexpected failures.

    BTW, at Richmond, I really thought that the #11 was running an extreme amount of camber, which has been a time-honored way to go really fast at that track. But as others found out in the past – extreme stagger is fast, but it can also put a car into the fence, without warning.

  8. First, let me tell Larry to bend over, grab his ears, and pull….. POP!!! Now that he has his head out of his rear end we can move on.

    Very informative article to say the least. Thanks for a well put together bit of reading.

  9. John: I think you’ve hit a very important point. A car is a system that is more than a simple sum of its parts. If you run extreme camber or this pre-yawed setup, you’re going to be loading the different parts of the tire differently. Since friction generates grip and heat, differential loading means different friction in different parts of the tire, thus different heat loads. It’s clear that Kenseth and Edwards were way overcambered at Richmond and that clearly led to tire problems. I could see the same thing happening with the offset rear end, especially if there is a lot more sliding than rolling. Thanks again for the great comment, John!

  10. ok, so when one of these “yawed” cars wrecks, how complex must it be to toe it back in? it just seems that it would be much more difficult than it is currently to correct that sort of moderate wreck, the kind that doesn’t end the race for the car but requires a whole ton of realigning in the garage.

  11. I’m not a gordon fan but he is the most accredited of the drivers in the garage. It should be his resposibility to speak for and represent the drivers side of the sport.

  12. Red,
    Setting the toe after a wreck will be no more difficult with a ‘yawed’ car than a car that isn’t. Toe refers to to how the tires point and is checked by measuring between the the front tires at the front of the tire and then at the back of the tire. The difference in these 2 measurements is the toe. It is not dependant on the rear tires.

  13. roger: thanks! i used the term incorrectly b/c, as you point out,”toe” refers solely to the front tires and the relationship between them.
    i’m more pondering if realignment after a wall brush, for example, is more challenging with the yawed cars or is it the same as its always been: one aligns tires, etc., in relationship to each other, not necessarily in relationship to the overall line of the chassis? it just seems that, with these cars so far out of “normal” that there have been difficulties in getting them into the inspection stations, it might be more difficult to straighten it up after a minor dustup.
    and — does jack rousch’s infamous “stolen” sway bar have anything to do with all this? hmmm. . .

  14. Hey Red: I’m going to see if I can get some expert input about this as soon as the long weekend is over. DLP

  15. So if maxima and minima of wheelbase are the limiting factor as to just how much yaw a team can build into a chassis , improving both the aero and mechanical ability to turn left , why not in respect of the true centre line of the chassis and a perpendicular off that line pull the left hand side front suspension forwards , and move the opposite side backwards ? NASCAR could investigate the alignment for all they wish , but unless they check the car against a true square extrapolated directly from the chassis , surely it is possible to produce a static measurement of less than one degree , whilst effectively having a much greater degree of yaw in the dynamic running ( i.e. , racing ) state ?

  16. Kevin,

    Let’s get somethin strait. Carl Edwards is working on his 5th full season with the rest of the #99 team. In ’04 Carl only ran like 8 races in the 99(less than a quarter). The ’05 season starts & Carl pulls off a sweet win @ AMS. The #99 team rolls on to “THE DEVIL’S TRIANGLE” & Carl just shows ’em how it’s done. & Then in the Chase the 99 team goes back to back @ AMS & TMS………& damn near win the Ford 400 too. ALL of ’06 was faught with out Bob Osborne, the 99 team came close to winning a few races but just couldn’t seal the deal. When the 99 team gets Bob back in ’07 all of a sudden the 99 team can win races even when Carl HAS A BROKEN & DISLOCATED THUMB(we all know that it doesn’t take any thumbs to hold onto a steering wheel)& the 99 team eeks out three wins. In ’08 the 99 team was in a league of their own. Daytona just sucks so no luck there. California the fastest car won. @ LVMS the 99 was runnnin the bumpy bottom line ALL DAY LONG do if a bolt brakes how is it the 99 team’s fault. The 99 was leading & had lead for 31 laps with 51 to go when the oil pan developed a hole. Ran out of gas @ Bristol. Ran out of gas @ Martinsville but still managed a 9th place. The Texas win was very dominant. A stupid rule cost the 99 a better finish @ PIR. Talledega SUCKS. finished 2nd @ Darlington to Rowdy. Ran out of gas in the 600 but still finished in the top 10. Had a DOMINANT car @ Pocono but with 30 tog the 99 rolls off pit road with a flat left rear. 400 mile races turn into fuel mileage races so the 99 team didn’t have a chance to with @ MI. & the rest of the season went like that.

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