RACECUBE^TM general information

Theory

Through its inventive software and algorithms, RACECUBE™ will first calculate the Chassis Centreline of the vehicle. Note, this is the ‘effective’ longitudinal centreline of the vehicle as determined by the wheels on the road. This is not necessarily the same as the Body Centreline, which, being dependent on suspension mountings and physical chassis structural alignment, may be skewed to it. The effective Chassis centreline is the true 'car dynamics' centreline relative to how the wheels are aligned and how the tyres are behaving on the road. This is a critical reference frame to find, as any inherent thrust angle at the rear wheels will be relative to it. The thrust angle will determine the true direction of travel of the car, whether front or rear wheel drive, and the closer it is to being zero relative to the effective Chassis centreline the better for vehicle dynamics, aerodynamics and for the designed elasto-kinematics. For precise vehicle dynamics calculations, this subtle difference is all too important as, typically, target toe angles are so small. The calculation of the Chassis centreline and thrust angle reference frames is all part of the RACECUBE™ magic. From this, precise toe alignment angles can be determined, presented and, if necessary, easily adjusted.

RACECUBE™ is able to calculate each of the front and rear wheel’s individual toe angle (c&d, and a&b) relative to the Chassis Centreline and also the total toe angles i.e. the included toe angles at the front axle and rear axle.

The driving direction, or Thrust direction, of the vehicle is determined by the rear axle wheel alignment relative to the Chassis Centreline.  This Rear Axle reference is also calculated by RACECUBE™. i.e. the thrust angle is determined by bisecting the total toe angles (a plus b divided by 2) seen at the rear axle such that there is zero rear tyre slip. This is true for rear wheel drive vehicles and front wheel drive vehicles.

If the calculated thrust angle is in the region of 5 minutes of a degree, you can use the Chassis Centreline reference to adjust the front toe angles as the misalignment is unlikely to have a perceptible effect for most drivers.

If the calculated thrust angle is between 5 and 10 minutes of a degree the theory can be looked at from two perspectives:

1. If the calculated thrust angle is under 10 minutes, then it may be acceptable to adjust the front toe angles using the Rear Axle Ref. i.e. the vehicle will crab slightly but the steering wheel can be centred relative to the driving direction. OR
2. If the calculated thrust angle is greater than 10 minutes then the recommendation would be to adjust the two rear wheel toe angles (keeping the same total rear toe) to realign the thrust angle to be coincident with the Chassis Centreline. With the steering wheel set to be level, the front toe angles should then be adjusted to the Chassis Centreline reference or indeed to the adjusted Rear Axle reference which will now be the same thing.