Hello,
I want to create simple racing game. Let’s make it even simpler - time trial racing game where you control diecast model of a car. Something similar to Hot Wheels Unleashed but without AI, multiplayer and all that stuff. Just driving on some track placed in a kids room.
I have prepared my car model, imported it into UE 5.2. Done all setups following official Unreal guides on how to make driveable car with chaos vehicle and it works great! Car is in real world scale. So it has real world dimensions and I want to create diecast model racer so should I continue as is and create environment that will be scaled up. Or should I scale skeletal mesh down and create environment in 1:1 real world scale?
I tried scaling car down in blender to around 24cm in lenght but boy, physics didn’t like it 
Of course I dialed down all settings in car blueprint like weight, wheel dimensions, suspension settings etc. and it even drives but it’s not even close to what I had earlier when it was 1:1 in real world scale.
Is this because chaos vehicle physics are not designed to be used in such small scale or maybe I am doing something wrong and should go back and tweak settings more?
So, first of all - disclaimer: This post will be just my opinions, speculations and ideas. I do not have a universal manual on how to do the thing you are trying to do, nor do I know wheather or not there is a “right way” to do it. But I can simply offer my point of view.
Wha I think is, you have to make a game design decision: Do you want your cars to feel like real ones, just scaled down relative to the world so it looks like models (let’s call this Option “A”), or do you want them to feel like toy cars (Option “B”)?
For Option “A”: I would keep the car real-scaled, including all the physics, and I would scale up the rest of the world. Why? I think the Option “B” parahraph will actualy answer this 
Option “B”: I would scale the model down for this option. But scaling the dimensions and weights is far from enough. And I don’t think the chaos vehicle physics is in fault here. To make the car feel like a model, you should replicate more of the model-like properties. Those diecast models, for example, have no suspension, so I would definitely make the wheels just pinned to the chasis. If I’d like to keep some suspension, I imagine there would be a ton of tweeking to make it feel right. I guess the forces in the suspension will not scale linearly, so just changing the weights will not solve it. Also the center of mas will have a different location on your model, torques/velocities/dampings/frictions, all that will have to be tweeked probably, to achieve a “toycar” feeling, if that’s what you are after. I would just try to replicate how a model car is put together and what forces are applied on it when driving, because just scaling a real car down is far from how model cars work…
Thanks for input!
I tried tinkering more in settings(tried to recreate toy car) but it is very hard as sometimes changes in suspension by 1 creates wild effects
So yeah I think I will go with option A for now as I reached out to some of my more experienced friends and they all said basically the same thing Scaling enviro up is way easier than setting up car physics for such small thing like toy car.
I would still love some more opinions, maybe someone tried it already and had interesting results
Strangely enough, this topic got somehow stuck in my head and I had one more shower-though to add Maybe If I’d like to go the “toycar physics” way, I would try ditching the chaos vehicle physics overall and go with a simply jointing the wheels to the body with appropriate axes locks and applying torque directly to tho wheels. This might actualy yield some pretty realistic results, since in reality, toycars are exactly like that, and the overly complex chaos vehicle physics would not interfere in any unpredictable way. It might even get computationaly cheaper that way 