About Anti-dive results on a KnC test (Baja SAE)

Question

Hello, I am validating the geometry for a double wishbone Baja SAE front suspension. After reviewing the results from the SDF file (KnC ride, roll and steering), I am having trouble interpreting the results. At 0s it shows an Anti-dive % of -13.46, the design value was intended to be 25%; the Anti-lift result seems to be more in line, showing -22.47%. Which one of the 2 results should I be looking if I have outboard brakes and what does the negative simbol mean? NOTE: I am using the baja/fsae libraries and MotionSolve 2025.0

GTT Adam · Answer

Hi @mauricio_muñoz17,

It's possible. Have you reviewed the animations for the KnC event when the model completes the longitudinal braking portion of the event? Have you looked at the strut lengths during that portion of the event? Are you analyzing a front suspension SDF or rear suspension SDF?

Have you tried running a full-vehicle dynamic version, such as the Straight Line Braking event?

Hope this helps!

Adam Reid

mauricio_muñoz17 · Answer

Hi @GTT Adam ,

Thanks for the reply. Does the negative results indicate that I have a pro-dive suspension?

GTT Adam · Answer

Hi @mauricio_muñoz17,

You should be considering both values, as anti-dive and anti-lift determine the resistance to diving in a front suspension or resistance to lifting in a rear suspension due to suspension geometry during braking.

In a suspension with 100% anti-dive/lift, the moment about the side view instant center due to weight transfer is exactly offset by the moment about the side view instant center due to the braking force.

More on the calculations being carried out in the SDF report can be found at the link below:

https://help.altair.com/hwdesktop/hwx/topics/motionview/sdf_anti-dive_lift_and_brake_dive_lift_r.htm?zoom_highlight=anti-dive

Hope this helps!

Adam Reid