BMW Camber Plates & Geometry Explained

Dialing in your BMW suspension for more than spirited driving sounds fairly simple, however, as we discussed in our previous article, BMW Coilover Buyer's Guide, suspension geometry is an involved process. The suspension components themselves can easily be interchanged for performance variants, but without knowing how everything works together and affects your handling, you will find it is not an easy task. This comprehensive analysis will help you understand tuning your BMW suspension for street or track performance driving.


Camber Angle

How your wheels rest when viewed from head-on is known as your Camber Angle. Anyone remotely familiar with suspension is likely aware of what camber angle is, but probably less familiar with how it affects your handling. The idea itself is simple: negative camber is when the bottom of the wheel is out farther than the top of the wheel, and positive when the bottom of the wheel is further in than the top of the wheel. Camber neutral is when the wheel is completely vertical and unbiased towards either positive or negative camber. The angles themselves are incredibly important for maximizing your grip and handling under different driving conditions.




Negative Camber

Negative Camber is more popular with drift cars, track cars, and has become a style for show cars in the last decade. The severe negative camber angles you may have seen allow for increased steering angle and for the fitment of more aggressive wheels. With proper negative camber, you are actually able to increase the contact patch of the outer tires when cornering, as the vehicle weight transfer will cause the camber angle to straighten to almost camber neutral under the load shift. Ideally, you will want to set your track or street performance BMW up with negative camber that allows for a good contact patch when the vehicle is loaded but has an almost square contact patch on the outer tires under hard cornering.


Positive Camber

Positive camber is used in drag vehicles, as the massive power and torque cause the vehicle weight to shift to the driven wheels and 'squat' the rear end. With the additional weight, the wheels are cambered back out to camber neutral under load, and the car is given the maximum contact patch and grip for the best launch possible. In track cars, positive camber makes steering very light on the front wheels and reduces the rear wheels traction in the corners. You will want to adjust your car’s suspension settings if you are seeing wear on the outside of the tires, as this will mean your camber angle is too positive for your driving. Note that you can have negative camber, but if your car is cornering and you are wearing the outer part of the tire, you may need more negative camber. This can also be caused by improper toe angles, which we will discuss later.




Camber Neutral

Neutral camber is when the wheel is square to the ground and would be completely vertical. This is how you want your wheel and tire for maximum grip. Why wouldn't you just set your car up with neutral camber for the best results? The weight shift from cornering, acceleration, and braking all change the load and angle of your wheels when you are driving. While you may have neutral camber sitting still, as you drive the contact patch will be reduced no matter where you are. The best use for your BMW to take advantage of neutral camber is to set your resting camber angle to account for load shifts to give your car a neutral camber angle where the most weight and power of your vehicle will shift under driving.


Adjustments

Camber angle can be adjusted with camber bolts, camber plates, and the orientation of your struts and shocks as they sit in the car. Your spring rates should be selected based on your camber angle and tires should be chosen that can handle the additional spring rates of your new setup. You can read more about the coilover suspension in our previous article BMW Coilover Buyer's Guide, and check out our Camber Plates for the widest range of adjustment settings to perfect your suspension setup.




Caster Angle

Caster angle is the position of the wheel in the wheel housing as you look directly at the face of the wheel, from the side of the car. This is how the car centers itself as you load a side by cornering. The caster angle plays a big part in how your steering behaves and can cause understeer or oversteer if it is not properly set.

You want to adjust your caster angle evenly on the front wheels to prevent any bias to one side. For your steering feel to be perfect, you will need to find a happy place between the positive and negative caster angle. Too positive and you will need excessive steering inputs and will experience understeer. Too negative and your car will oversteer and you will have reduced steering feel. Dialing in your caster angle will take a lot of trial and error as you perfect the angle for your lowered suspension and added negative camber.


Toe Angle

The toe angles of your wheels are the angle of the wheel left and right when viewed head-on. Similar to camber angle, but on the opposite axis. Toe out points the wheels away from the wheel centerline of the vehicle, while toe-in points them towards the center line. Zero toe is where they are completely in line with the vehicle.

The toe angle is incredibly important to keep the vehicle driving in a straight line and not bias towards one side under braking. Minimal changes in your toe angle can have massive effects on your vehicle's performance. Excessive toe, either in or out, causes severe tire wear and poor handling.


Spring Rate

The spring rate is the ratio of resistance based on spring compression by one inch. This is the weight your springs require to compress. Spring rates and lengths are selected by the vehicle weight, height, and angle at which the struts/shocks are mounted in the car. The proper spring rate is selected based on a formula of how all those values relate to each other. The lower your vehicle, the stiffer your spring rate needs to be in order to prevent the vehicle from bottoming out, but you do not want to exceed the ability of your tires to maintain grip. Too stiff and you can actually decrease performance as we learned in the last article covering coilover functions.




Strut Housing Angle

The angle at which your struts and shocks are mounted is referred to as your strut housing angle. This angle can affect your camber angle, which will need to be adjusted properly if you change the orientation of your struts and shocks. This angle also affects your spring rate, and there is a specific formula to determine how stiff your springs need to be to maintain an identical rate to your previous housing angles. The change in angle shifts the way loads are distributed to the car through the suspension and can improve the effectiveness of your suspension, but will increase the overall harshness of the ride as you reduce the degree of the angle of your housings.




Roll Center

The roll centers of your BMW are the points around which your suspension pivot. These points change under acceleration, braking, and cornering. The further from the center of gravity the roll center is, the more weight is transferred there as the load shifts. You want to balance the front, rear, and corners of the car so that your roll centers are neither too high nor too low. This will allow your chassis to roll linearly and keep your car balanced through corners. This can be achieved with an evenly lower center of gravity, properly adjusted suspension geometry, and corner balancing.




Corner Balancing

Corner balancing adjusts the weight and load distributed to each wheel so that the range is optimal for your suspension function and load shifts during driving conditions. This is adjusted with the spring rate and height. You want your suspension to handle evenly across all corners in a street or track performance BMW, so corner balancing is important. Think of it like you would engine software tuning after you have added performance bolt-on modifications. In order to achieve the best results, you need to fine-tune the suspension so it all works together in harmony and equally across all four wheels.




Takeaways

While it is important to choose your suspension upgrades wisely, you also need to know how to effectively dial them in for proper function. The ratios at play are all determined by the constant of physics, so there are easy formulas to determine your proper suspension settings. Once you have your suspension installed, you can easily fine tune the camber, caster, toe, and housing angles to provide an optimal center of gravity, optimal roll centers, and can corner balance the vehicle for even load distribution. These settings will allow you to take full advantage of your upgraded suspension and perform to your fullest ability on the track with your BMW.