So far I've got a motorcycle attached and acting like a real motorcycle. Which means it tips over.

How can I prevent this? I've uppsed the mass of both wheels to 1000 and given the bike a mass of 1, and this helps some, but tips slower, and not much slower.

I've considered the idea of an invisble entity that would only allow the bike to tip so far, but I want to leave this as a last resort.

Any help is appericated.

Based on my sketchy memory of physics 101, I think that the main thing that stops a motorcycle (or a normal bicycle) tipping over is the rotational inertia of the wheels when they are in motion. A gyroscopic effect means that trying to tilt a spinning wheel takes a reasonably large amount of work. I don't know how you would go about building this into the physics environment, but that's what you need to simulate.

Lowering the centre of mass for a four wheeled vehicle means that it is harder to move the centre of mass past its base of support, thus increasing its stability. On a two wheeled vehicle it will just mean that the tipping force acts differently.

If that's wrong then someone tell me, but I think I've got it right. Sorry I can't actually help you.

You will need to add an invisible entity. Such an entity would also be a physics entity constrained via a hinge joint to your motorbike. Or, you can try to fake the bike effect by having 4 wheels in close proximity with 2 invisible. I have gotten a motorbike working with the first method and it works quite well. The only problem is that the bike leans the opposite way that it does in real life. I've gotta try figure that part of the problem out tonight...

I had conisdered adding Training wheels to the bike. Maybe a bit off the ground that way the bike can tip only so far. But this might interfer with with collision with terrain walls or even other motorcycles in the game.

What sort of effects do you want the bike to have? If all you need the physics for is gravity, jumps and collisions then you could manually tilt the bike according to how fast you are turning - I can help you with the physics equations there if you like - while using things like gravity to determine the position of the entire bike in space as a single entity. You could even do things like wheelies this way, but it will involve a lot of computation by yourself. The added benefit is that this would probably only require one physics entity, so you will only need the professional version.

What sort of context will you be using it in? This would be fairly easy to implement on a superbike race course, harder to implement on a dirt-bike track and difficult to do for a city street.

Rephrased (I hope) more clearly, you would use the physics engine to keep the bike on the ground and prevent collisions, but you would use your own code to tilt and turn the bike. Of course, if you wanted a really spectacular crash, you would need to enable physics for each part of the bike, rather than as a whole, but you could do that the instant the rider looses control of the bike.

Thanks, I'll private message you on this.