I don't wanna my car pitch or roll

my car is a bumpercar which has no wheel, so I just wanna it collision with others and forward ,backward or jump( Y-axis movement), but now,as soon as heavy collision happens,my car will pitch or roll (flip over), I have tried to set CMass to (x,0.1,y),but it still flip when in a high speed collision. Have u any methods to stop these things ?

Do you mean the car has no WheelShapes? You can limit the direction of travel, the method name escapes me this moment but it's in Actor. You specify which directions you want it to move and don't move in.

Do you mean the car has no WheelShapes? You can limit the direction of travel, the method name escapes me this moment but it's in Actor. You specify which directions you want it to move and don't move in.
I can't find the method you said in actor....
now I invented another method,to setMaxAngularVelocity to Zero,and it does work!

Do you mean the car has no WheelShapes? You can limit the direction of travel, the method name escapes me this moment but it's in Actor. You specify which directions you want it to move and don't move in.
can you tell me thsi specified method? I am keen on using it!

Not entirely sure but you accomplish this with freeze flags.
NX_BF_FROZEN_POS_X
NX_BF_FROZEN_POS_Y
NX_BF_FROZEN_POS_Z
NX_BF_FROZEN_ROT_X
NX_BF_FROZEN_ROT_Y
NX_BF_FROZEN_ROT_Z
NX_BF_FROZEN_POS
NX_BF_FROZEN_ROT
NX_BF_FROZEN
NX_BF_DISABLE_GRAVITY
raiseBodyFlag(NX_BF_FROZEN_ROT_X);

Not entirely sure but you accomplish this with freeze flags.
NX_BF_FROZEN_POS_X
NX_BF_FROZEN_POS_Y
NX_BF_FROZEN_POS_Z
NX_BF_FROZEN_ROT_X
NX_BF_FROZEN_ROT_Y
NX_BF_FROZEN_ROT_Z
NX_BF_FROZEN_POS
NX_BF_FROZEN_ROT
NX_BF_FROZEN
NX_BF_DISABLE_GRAVITY
raiseBodyFlag(NX_BF_FROZEN_ROT_X);
it's wonderful! how can u know that without enough NxOgre Documents?

There is a 27 Meg document that comes with PhysX that tells you these things. If you haven't noticed already all the methods in Actor are the same in NxActor which are documentated in said PhysX documentation.