Mazda6Tech - Mazda6 Camber Analysis Mazda6Tech - Mazda6 Camber Analysis

In the above picture, the car is turning right and leaning to the left. That causes the upper A-arm of the left tire (pictured on your right, if you're having trouble following) to swing up and inwards (negative camber). Without this swing inwards, the car's tires would be parallel to the car's body and would have positive camber. The inside wheel changes camber just enough to not lean with the car, and remains vertical. Again, without the change in camber, this wheel would not be vertical- it would have rolled the same direction as the body. The outside (compressed) wheel gains more camber relative to the inside wheel because the short upper A-arm pulls the tire in more towards the end of its suspension travel.

This is an important concept! The suspension on the Mazda6 may only gain half a degree of camber in its first inch of suspension travel, but it could gain almost a full degree in the following inch of travel! A McPherson strut suspension, used in everything from the front of a BMW M3 to the Mazda3, does not do this. A strut type suspension could gain the same half a degree in its first inch of compression, but would gain less than half a degree beyond that.

This extra camber on the compressed tires is great, as the outside tires bear the majority of the car's weight through a turn. As such, those tires will also have to bear most of the lateral cornering force. The outside (loaded) tire are the most important tires to tune for!

Camber Analysis of the Mazda6

This, in a nutshell, is not unlike the Mazda6's suspension. Unfortunately, unlike the above drawing, the Mazda6 has more body roll than it has camber change in a turn. Thus, the tires go off-camber during turns, forcing the tires to wear on their edges and sacrificing a significant amount of grip.

In the picture to the right, you can see the pronounced body roll caused by sharp turning. By taking a picture straight on such as this, one can rather reliably measure body roll. In this case, the body has rolled 3 degrees. Thus, to keep the tires "on" camber, the suspension will have to have gained three or more degrees of camber in the direction opposing this body roll. In this picture, it is hard to tell if the outside tire is still vertical or not, but the inside tire is definately off-camber. Remember the outside (loaded) tire gains negative camber more quickly.

The following picture shows us the outside (and more important) tire more closely. It appears as if it, too, goes "off" camber in turns. Because going off-camber places the weight on the outside edge of the tire, you can see the sidewall of the car folding in under the wheel: Mazda6Tech - Mazda6 Camber Analysis

The real tool to determine if a wheel is going off-camber is a pyrometer. It measures tire temperatures, which are indicitive of what part of the tire is being worked the most. An off-camber tire will be warmest near the outside edge of the tire, while the inside will remain cooler. Unfortunately, the author does not have one available, but there is another fairly obvious way to tell:

Note the extreme wear on only the outside edge of the tire. These were made after just several minutes of hard driving. The "chunks" and coarsness of tire missing are from the tire overheating and essentially falling apart under the load. Mazda6Tech - Mazda6 Camber Analysis

Correcting for More Negative Camber

Now that the problem is identified, we need to try to fix it. There are two ways to do this: reducing body roll and increasing negative camber.

Normally, camber can be adjusted by an alignment. That is, the suspension is changed so that while at rest, it has negative camber. When compressed, it still gains the same amount camber, thus it has even more negative camber. However, the Mazda6 only comes with camber adjustment in the rear of the car. Unfortunately, being a front-wheel-drive car, most of the weight of the car is over the front wheels, not the rear. It is imperative that camber be corrected in the front, where it unfortunately lacks this manual adjustment.

Getting negative camber in the front can be accomplished by lowering the ride height of the car. Conversely, you can reduce the need for additional negative camber by reducing body roll. Most aftermarket springs will do both. Recall that the tires gain negative camber during the compression of the suspenion. If we lower the ride height via different springs, that negative camber is gained in the same manner. At rest, the Mazda6 will have negative camber so that during turns it will have more.

An alignment shop revealed that after installing the Eibach lowering springs, which drop the rear of the car 1.4 inches and the front 1.5, camber has changed a considerable amount. The front of the car now has 0.8 degrees negative camber (0-0.3 stock), while the rear has 1.5 degrees negative camber (0.5-0.7 stock). To the naked eye, the negative camber can be seen in the rear tire of the picture.

The rear has more static negative camber than the rear because the front gains camber as the wheels turn left and right. Because the suspension is not mounted perfectly vertical, the wheels actually rotate a few degrees along a horizontal axis. Look at the following picture:

The outside-front wheel will gain negative camber, while the inside-front wheel will loose its negative camber and possibly even have positive camber. Thus, both wheels are leaning in the direction of the turn, which is optimal. Thus, depending on how sharp the wheels are turned, the front of the car can have not only more negative camber than the rear, but both tires on camber.

The camber gained while turning is a good thing, as it allows static camber for the front wheels to remain low while still having good camber in turns. Since the front wheels do the vast majority of the braking and all accelerating in the Mazda6, this is especially important in the front. Recall that any camber, be it positive or negative, is bad for acceleration and braking. Generally, once a tire sees more than 1 degree of negative camber, it's braking and acceleration performance starts to depreciate rather rapidly. For autocross, this is not as important as lateral grip, but for track racing this may be an area not worth compromising.

When braking, the front suspension will dive down even further, increasing camber further- perhaps enough to create a large reduction in braking traction. Just the Mazda6Tech - Mazda6 Camber Analysis

opposite, however, is acceleration- throttle lifts the front of the car, reducing negative camber and making the wheels slightly more vertical. This difference is minor, however- the front of the car will not lift the full 1-1/2 inches required to get back to 0-degrees camber. Thus, a spring that lowers the car less than the 1.5 inches pictured may have better braking and acceleration performance. Without lowering the car to gain camber, controlling body roll will be even more important, and thicker anti-sway bars are probably necessary.

The owner of the pictured car hopes to have lowered the car enough to not need anti-sway bars. To determine whether or not the camber gained is sufficient, we need to know how much body roll has been reduced. Recall that body roll was 3 degrees, and so the tires will need to gain at least 3 degrees of camber in the opposite direction to compensate. To measure the amount of the car's body roll, once again pictures must be taken on a track:

Observe how turning the wheel slightly caused the inside wheel to lock and smoke. An off-camber tire is not suitable for braking. The outside tire did not lock up because it is still vertical throughout the turn and has more grip.

In the following picture, we see the same car at its cornering threshold. Body roll looks to be reduced to about 1-1/2 degrees, in other words it was cut in half.

Although not directly visible in the picture, we can still draw some conclusions. If the car is only rolling 1-1/2 degrees and the rear has that much static camber, we know the outside rear tire is going to have at least some negative camber in the turn. The inside-rear tire is off-camber, but it is insignificant. It bears very little weight and is not responsible for much cornering responsibility. In some cases, it may even lift off the ground. In the front, the camber change from steering has Mazda6Tech - Mazda6 Camber Analysis