in <handlingName>VXR</handlingName> change vxr to ur car addon name

 or manually:


STEP-BY-STEP  (Edit addon car suspension)

Open OpenIV - navigate to:
turn on edit mode
mods > update > x64 > dlcpacks > (ur addon car name)>dlc.rpf(double click)
then common > data then click edit on [ handling.meta ]

under ur car handiling entry (eg: <handlingName>VXR</handlingName>)

change value of following to

fSuspensionForce        1.5
fSuspensionReboundDamp  0.40
fSuspensionCompDamp     0.50
fSuspensionUpperLimit   0.16
fSuspensionLowerLimit  -0.23
fAntiRollBarForce       0.3

then clcik save 
launch the game

STEP-BY-STEP  (other game car suspension)

Open OpenIV - navigate to:
turn on edit mode
mods > update > update.rpf > common > data>handling.meta(click edit)

under ur desired car handiling entry (eg: <handlingName>VXR</handlingName>)

change value of following to

fSuspensionForce        1.5
fSuspensionReboundDamp  0.40
fSuspensionCompDamp     0.50
fSuspensionUpperLimit   0.16
fSuspensionLowerLimit  -0.23
fAntiRollBarForce       0.3

then clcik save 
launch the game