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Design Guidelines

Checklist of Kinematic Parameters for a New Suspension Design by GregLocock
Posted: 19 May 04 (Edited 19 May 04)

Here's a list we compiled of the suspension-related kinematic characteristics that need to be considered when designing a vehicle from scratch. By its nature this is a top down approach. I've tried to edit out the redundant entries, but can't claim it is 100% sorted. It obviously is not complete, let me know if you want to add things.

1 WHOLE VEHICLE:

Sprung mass
Sprung CG X and Z
Moments of inertia
Maximum steady state lateral acceleration
Ground clearance
roll stiffness (degrees per g of lat acc)
ride frequency, including front to rear percentages  
lateral weight transfer percentage distribution front to rear
Torsional stiffness of the body structure
Roll axis gradient and any gradient change relative to roll
roll couple distribution

2 AXLE and WHEEL:

2.1 Packaging and general
spindle length
position
track
tyre size, hence rolling radius
Jounce travel
rebound travel
wheel offset
unsprung mass

2.2 Toe
Static toe setting
Ride Steer
Roll Steer
Tractive Force Steer
Brake Force Steer

2.3 Camber
static camber
Ride Camber
Roll Camber

2.4 Castor
static castor setting
castor gain
castor trail

2.5 Roll centres
roll center height at design load
roll centre height gain
TLLTD (tire lateral load tranfer distribution)

2.6 Track
track gain in roll
semitrack gain, ie lateral displacement of contact patch per unit of jounce travel

2.7 King Pin Geometry and Steering
KPI
scrub radius
steering axis angle
hub trail
pin lead/trail
Ackerman percentage/change
steering ratios
Lateral force steer (deg/g)
Aligning torque steer (Nm/deg)

2.8 Compliances
Stiffness of the major suspension mounting points, ie on a McPherson Strut, do the strut towers move around
Aligning torque Camber compliance (small effect)
Lateral Stiffness (at ground w/o tire)
Fore-Aft Stiffness (at wheel center w/o tire)
Lateral Force Camber Compliance

2.9 Other
Anti-x
Side View Swing Arm Angle (SVSAA)

Contributors:
pmwltd
hpfreak
patprimmer
TestDriver
MattPurdy
2SlowJoe
GregLocock

Back to Automotive suspension engineering FAQ Index
Back to Automotive suspension engineering Forum

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