Not even the most talented publicity person could convince NASCAR fans that the idea of giving teams a choice of a ‘soft’ tire and a ‘regular’ tire was a good idea based on the sole data point we have: the 2017 All-Star Race. The idea that having one set of ‘option’ tires which were softer and thus wore out more quickly was touted throughout the press in the days leading up to the race as a way to ‘Return the Magic’ to the moribund All-Star race.
It didn’t work so well. So is the idea dead?
You Can’t Have It All
Let me remind you of the ‘Magic Triangle’: the holy grail for tire designers.
The diagram is a three-dimensional picture — the slanted blue plane is the surface nature constrains us to. What this diagram says is that you have three properties you’d like from a tire:
- Wear resistance (they last)
- Heat Dissipation (they don’t blister)
- Grip (they hold to the track)
In an ideal world, you get all three, and as much as you want of each. In the real world, it doesn’t work that way because you can’t tune all three of them independently. Think about it. If I give you a hard rubber donut, that puppy isn’t going to wear, but it’s also going to get very hot and it’s not going to grab onto the track very well. If I give you a squish soft tire, it’ll grip, but two laps in and it’ll be a molten mush of rubber.
Soft vs. Hard Tires
When non tire designers talk about tires, we mostly talk about ‘hard’ tires (meaning they don’t wear quickly, but also don’t have as much grip) and ‘soft’ tires (meaning they’re really grippy, but they wear quickly).
In theory, having a softer and a harder tire is designed to increase the strategy options for the teams by allowing them to choose between grip and wear.
Let’s put a driver on the track with a new set of tires and have her make forty laps, driving every lap with the same line and trying to go as fast as possible.
The lap times won’t be the same. In fact, the first laps will be the fastest and the lap times will increase the longer the run wears on. We call this ‘tire fall-off’, which is an unfortunate term because it does sound like the tires are falling off the car. What ‘fall off’ refers to is the car’s speed. That correlates to an increase in the laptime. I’ve sketched out what this might look like below. I didn’t put any numbers on the lap times because they’re different for every track and every type of time.
The largest part of the fall-off happens in the first few laps — that’s why we talk about the advantage of new tires (hard or soft) over old tires. After the initial fall-off, the lap time continues to increase, but it happens a little more slowly. We’ll have our driver repeat this 40-lap excursion for the hard tire and the soft tire.
Two things change when you change tires
- The shape of the fall-off curve
- The starting lap time.
A soft tire falls off more quickly in the first few laps than a hard tire — but the soft tire (because it is grippier) starts out faster. If we compare the soft tire’s falloff to the hard tire’s falloff, we get the graph below. Remember that we want smaller lap times, so lower on the graph is better.
At first, the softer tire is faster. NASCAR was aiming for somewhere around 3/10 to 5/10 of a second faster. But as the laps continue, the soft time wear faster than the hard time, so at some point, an old hard tire is better than an old soft tire. (New tires almost always win.) NASCAR said in their press materials that the soft tire should wear out in about 20 laps, which I’ve tried to get close to in my diagram.
We can plot this data in a slightly different way: By looking at the Hard Tire Lap Time (HTLT) minus the Soft Tire Lap Time (STLT). If the number is positive, than the soft tire is faster. If the number is negative, than the hard time is faster.
The idea is that the soft tire is faster for awhile, then the hard tire is faster. This gives the crew chief options. They might use softer tires and get enough of a lead during those first few laps that the field won’t be able to catch them when the soft tires start to go away — or maybe they’ll luck out and there will be a caution. Then everyone will get new tires. They have to decide, though: Do you want the soft-tire advantage at the start of the race? In middle? At the end?
Why more crew chiefs don’t have nervous breakdowns, I don’t know. You’ll notice, though that it’s rare to see a crew chief survive at the Cup level as long as a driver. (There are notable exceptions, like Chad Knaus, of course.)
Great Theory. But It Didn’t Work.
I know. NASCAR knows, too.
Do you know how WD-40 got it’s name?
I’ll give you a hint. The name stands for Water Displacement, 40th formula.
Yep. The product you buy today was the 40th attempt at making a formulation that worked.
Edison tested something a huge number of different light bulb filaments before he found one that worked and made the incandescent light bulb a household fixture.
Things don’t always work the first time. In fact, things rarely work the first time. You have a choice: You can say you failed and give up, or you can take what you’ve learned and try again.
And while we’re on the subject, Edison did NOT try out 10,000 different materials before he found the right one for the incandescent light bulb filament. That was a marketing ploy, designed to convince consumers that they were getting a really, really good product that had been through extensive testing. They did try a lot of different filaments, but the number seemed to grow with each new marketing campaign.
What Did We Learn
I’m not privy to all the data NASCAR has, so some of this is my intuition and guessing.
Tuning the Tire. NASCAR said they were looking for a 3/10 to 5/10 of a second advantage for the soft tires and GoodYear said that the goal for the soft tires was for them to “at least one 20-lap run“. The graphs above show that the key is how long the soft tires maintain their advantage over the hard times. The quote about lasting at least one 20-lap run doesn’t tell you anything about how fast they lose their advantage. Do you make them so they’re faster for five laps or for ten laps?
You’re asking Goodyear for a Goldilocks tire. It has to run really fast for a short time, then degrade — but it can’t degrade so quickly that it blows out.
That’s not an easy spec to meet.
Wrong Race for Testing. If you’re going to make the soft-tire option work, you have to take into account how long green-flag runs typically are — and that’s not something that’s predictable. Let’s look at typical green-flag runs at 1.5-mile tracks. The graph at right shows three 1.5-mi races from this year, with the stage format.
|Race||Shortest Run||Average Run||Longest Run|
The All-Star race is a totally different context than your average 1.5-mile race. Any tire Goodyear would have to develop as a soft ‘option’ tire would have to be able to last a lot longer than one 20-lap run.
There didn’t seem to have been enough of a falloff in those 20 laps to make a huge difference. If they had tried this on a longer race, it might have had very different results.
Sometimes, you’re just not going to have a super-exciting race. In my opinion, NASCAR is now trying way too hard to manipulate race rules to make every race edge-of-your-seat exciting.
I learned early on from my father that sports aren’t all about the game. Baseball, to me, was never just about watching people pitch, hit and field a ball. It was about Vienna sausage, sauerkraut and beer. It was about spending time with family and friends. It was about meeting people at the ball park you normally wouldn’t meet. It was about bonding over the miserable prospects of a struggling expansion team.
Too Many Rules. The reason I was excited about NASCAR introducing a soft tire was because the box the teams must work in has become smaller and smaller, especially in the last few years. There is little room for innovation for the teams. Giving them options for tires is a way to give the teams more opportunity to take chances with strategy, to make daring choices.
But the rules developed for this implementation were needlessly complex. They led to crew chiefs trying to come up with clever interpretations of the English language instead of scientific or strategic innovations.
If two tires are going to work:
- I get why they limit the number soft tire-sets. But giving everyone one set and requiring them to use that set is a gimmick, not a way to expand the box.
- Don’t call it an ‘option tire’ if you’re going to require teams use the soft tires. A softer tire should be a choice for the team that they can employ if they want.
- Don’t require the soft tire be used at a particular time in the race.
- Don’t require they be used as a set.
- Definitely don’t attach an artificial penalty if the teams use the tires.
If two tires is going to work (“work” meaning make the racing better), it’s going to be because the softer tire has advantages and disadvantages that can be exploited by clever crew chiefs and drivers. Not because NASCAR has tried to artificially engineer the situation.
As I’ve mentioned before, we have to acknowledge that NASCAR is in a pickle with making changes. If you’re going to implement changes that address race strategy, you need to test them in a race. They clearly couldn’t test the tire during a points race. The All-Star race was the only choice.
I hope NASCAR doesn’t give up on the two-tire option. Imagine if the guys who invented WD-40 had given up after one try. Or 39 tries.
A parting thought:
Also published on Medium.