I'd reccomend to discard the physics engine in favour of a c_move/c_trace/c_rotate based solution for your movement. I had nothing but trouble trying to get a vehicle to work right, reason being is that you cannot have midly high poly worlds without there being terrible jittering. This is a confirmed bug to and I have no idea if it would be fixed or not, but that doesn't matter. It took me 1 month and 1 week to completely re-do all the movement and shift all the related systems to it. Honestly, by hand coding it you can put in independant suspesion, powersliding, strafing, and all other manners of movement without being restricted to the barriers of the physics engine.

Heres some code for entity-entity collision:

Code:

---

  function collide_move()
{
  vec_diff(temp,my.x,you.x);
  vec_normalize(temp,1500);//strength of force
  //vec_add(my.x, temp.x);
  c_move(my, nullvector, temp.x, ignore_passable + glide);
  vec_diff(temp,my.x,you.x);
  vec_normalize(temp,1500);//strength of force
  vec_inverse(temp.x);
  c_move(you, nullvector, temp.x, ignore_passable + glide);
}

---

It moves the my and you entities away from eachother. Put it in a while loop with smaller values for each entity and you can simulate a good force. I'd seriously reccomend not disabling and enabling the entities as physics entities just for collision(as this can be easily scripted).

P.S - The only way the physics engine would be good for movement is with a slower moving vehicle on a low poly world. Also, A.I can slow things down alot with physics enabled cars, so don't intend on having large races going on. I'm not trying to be a defeatest here, but please consider what i'm saying, since it really sucks when you find you wasted a couple months monkeying with something that just wont work. Especially when you have a TON of other systems tied into it(turbos, weapons, characters, ect.). But then again, if your a novice coder i'd reccomend first using the physics engine to get your grounds with movement, since you can crank something out very fast with the physics engine(think 1-2 days) in contrast to some very complex hand coding that will take at least a month.