How Cambered Tires Work

As the legend goes, the Greek philosopher Archimedes discovered the principle of water displacement while getting into his bathtub. He proceeded to run naked through the streets of Syracuse shouting “Eureka!”

Which of course sounds pretty crazy until you realize that “Eureka!” is actually Ancient Greek for “Help! My bathwater is too hot!”

John Scott, the inventor of Cambertires, had one of those quintessential Eureka moments one day; that flash of brilliance that suddenly looks at the world sideways and generates an idea so simple and yet so deep that no one had ever thought of it before. “What if tires had camber built in?” His vision may yet change the world of tires in a deeply fundamental way.

It's easy to write something like that, but perhaps not quite so easy to explain it:

As many readers may know and just as many may not, camber is an alignment setting that determines how the tires sit in relation to their up/down axis. If the tire is straight up and down in relation to the car, it has zero camber. If you set the alignment so that the top of the tire leans in towards the car, this is called negative camber. If the top of the tire leans away from the car, this is positive camber.

Camber is used for nearly all vehicle applications, but major negative camber is used most often for performance applications, where it can have positive effects on things like weight transfer, body roll and contact patch placement during tire distortion. Race car drivers use camber on oval tracks, where they can set the one side's camber as positive and the other side as negative to make the car turn quicker in one direction by getting maximum contact patch when under load. Setting negative camber on both sides is effective for road tracks in which the car turns both left and right. The issue with using camber is built in to the tires. If you dial in some camber, your tires are now tilted and the tread surface is not flat to the ground anymore when the car is straight. This will lead to large amounts of irregular wear on the inside of the tire and some loss of contact patch under acceleration and braking. This is where John Scott comes in.

Mr. Scott calls current tires “square”, referring to the casing profile of the tire, an effective 90 degree angle between sidewall and tread. Place a “square” tire on its tread and it stands straight up and flat to the ground. Mr. Scott's Cambertires, on the other hand, have a constantly variable diameter from the inside to the outside sidewall. That's what his patent says. The tire's diameter is larger on the outside edge than the inside, so that the the tread surface is on a diagonal. Put these tires on the ground, and they sit tilted off-center. These are tires with camber “built in.” So if you set up a 4-degree Cambertire on a car with zero camber, straight up and down, the tire would be riding on its outer edge, with a gap between the rest of the tire and the ground. But dial in 4 degrees of negative camber, and the tire is tilted slightly towards the car, but resting flat on the ground.

According to Scott, the Cambertire provides increased lateral grip, improved braking, better steering feel, more even wear, better ride quality and higher fuel efficiency. It sounds crazy, I know. I had some difficulty wrapping my head around it all. But it certainly seems to work.

Automobile Magazine looked pretty closely at the concept several years ago, and emerged ready to put Mr. Scott's name on a level with rubber pioneers Charles Goodyear and John Dunlop. The article noted: “Tire engineers would kill for any one-percent gain. Trimming braking distance by six percent while increasing cornering grip by four percent constitutes a major breakthrough.”

Matt Farah of The Smoking Tire also expressed some surprise during his test drive: “I didn't want to believe this guy... On the other hand, these tires are very, very good.”

So what is it that makes cambered tires work better? Put it this way: If you put a square tire on the ground and push it, it wants to roll in a straight line. To make it turn requires some force. To make it turn at speed requires enough force to overcome it's own tendency to roll straight plus the straight-line inertia of the car. But put a cambered tire on the ground and push it and it wants to roll in a circle towards the lower-diameter edge.

Now translate that to when the tires are on a car turning hard to the right. The right-side tires are cambered slightly left, and vice-versa, while all four tires are flat to the ground. During the turn the weight transfers to the left side and the left front tire is doing most of the work. That tire is not only getting all the suspension effects of camber, not only flat to the ground with the entire contact patch gripping the pavement, but it wants to turn to the right. The more compression is put on it, the more it wants to turn.

The right-side tire, on the other hand, has much less weight and pressure on it, and is tilted over toward its larger diameter outside edge. The much narrower contact patch makes it act like a bicycle or motorcycle tire, offering much less resistance to the turn than an unloaded square tire would. Scott's company now also sells certain of its tires with “rockers” that extend the outer sidewall and act something like the outriggers on a sailboat for even greater stability in this condition.

Now if you imagine a right triangle, a little Euclidean geometry will prove that the angled side is always longer than the longest straight side. Because of all that geometry stuff, the angled contact patch on a cambered tire is also going to be a wider surface than it would be on a “square” tire of the same size.

When the tires are rolling straight, the camber effects seem to counteract each other, almost like a natural form of “toe-in” where the tires on each side are aligned to roll slightly towards each other. With square tires a certain amount of toe-in is necessary. But Cambertires, Mr. Scott informs me, do not need "toe-in" at all. That lack of toe-in makes for less tire scrub, cooler running temperatures, less rolling resistance and better treadlife.

The interesting spiral tread pattern cut into the tires may also contribute to straight-line stability and hydroplaning resistance. The single void that spirals around the slick tread is wider on the inside for water evacuation and narrower towards the outside for tread stability. Scott calls the technology Assymetrical Helical Tread and Void Design.

That may also have something to do with another jaw-dropping effect Mr. Scott claims for his cambered tires. Even with almost no tread pattern and no siping patterns at all, he maintains that they have an amazingly good grip in the snow. That's a bold and entirely anecdotal claim, and one which initially sounds kind of insane. From anyone else I might take it as sheer boosterism. But...quite a few of Mr. Scott's claims sound a little wacky at first, and most of them have stood up to the scrutiny of multiple expert skeptics who have subsequently become believers. I would certainly love to see what could happen with a winter compound and tread pattern on cambered tires.

So on the one hand, this is an idea so simple that it's a wonder no one has ever thought of it before, and on the other it's an idea so counterintuitive that it's a wonder that anyone would think of it, much less try it out on actual tires. And yet, it still moves. Eureka!