Steering System Compliance

[aj14]

i am working on understeer budget calculation and i am trying to find out steering system contribution to the understeer. I am trying to calculate steering stiffness with Steering Wheel Torque Vs Toe Change. so as to find how much steering torque is required to turn 1 deg of wheel center. Is it the right way or am i completely off?

[aj14]

i am working on understeer budget calculation and i am trying to find out steering system contribution to the understeer. I am trying to calculate steering stiffness with Steering Wheel Torque Vs Toe Change. so as to find how much steering torque is required to turn 1 deg of wheel center. Is it the right way or am i completely off?

[BillCobb]

You are on the right track. Because of frame flexing, gear teeth, u-joints, wheel bearings, etc., this function can be highly nonlinear (soft on-center). So use the derivative of your data to study the understeer effect. This is usually a sizable portion of the understeer pie chart (as in 25% - 50% in street cars. Power steering valve shape is another big contributor (beyond this forum). A 2 term exponential function usually makes a great math model for representing this relationship. First term is initial stiffness, second is the displacement to 67% of metal to metal.