BMW E70 Chassis Dynamics

If a lateral tire force is acting on the wheel, a braking or accelerating force (tangential tire force) can only build up in a longitudinal direction up to the maximum total force (resulting force on surface). When this is reached, the wheel locks or spins. Conversely, only a limited lateral cornering force (lateral tire force) can be achieved under braking. If this is exceeded, the wheel slips in a lateral direction. This causes the vehicle to skid. If a braking force takes effect, the full lateral cornering force can be established in accordance with the radius of the Kamm's circle.

In the same way, the full braking or acceleration force can be established when the vehicle is driving straight ahead (again according to the radius). This relationship shows that acceleration or braking that is too rapid under cornering can cause the vehicle to skid, as any longitudinal force on the wheel, whether it serves to accelerate or brake, inevitably results in a failure of the lateral cornering forces. The radius of the Kamm's circle depends on the friction coefficient between the tire and the road, i.e. on the tire, the road surface and the road conditions. If the road is wet, for example, the radius is considerably smaller than if the road is dry.

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2000+ BMW X5 Front Installation Instructions

Most 18” wheels will clear the outer diameter of the caliper on a 355mm kit. However, the more critical clearance is the gap between the spokes of the wheel and the face of the caliper. Do not assume that a 19”, 20” or even 24” wheel will clear the face of the caliper. The actual metal-to-metal distance measured from the stock rotor face to the inside of the wheel spokes is 62.25mm for the BMW X5 front kit. StopTech recommends at least 2mm of additional clearance. See the Wheel Fitment Drawing page on the StopTech website for more specific measurements, at www.stoptech.com. Note: Final fitment of the wheel to the caliper is the responsibility of the customer.

Wheel Spacers
Wheel spacers can provide extra clearance to the outer face of the caliper. This will also space out the entire wheel, widening the track width of the vehicle. Fender clearances should be checked on lowered cars, and longer lug studs or wheel bolts are usually required. Note: The Wheel Industry Council has issued guidelines advising that wheel spacers not be used. It is the responsibility of the customer to ensure that wheel spacers are properly specified and installed.

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