Works as it should, if a heavy part is on top of the car it’s suspension will go down with it. It doesn’t make the car move side to side like how players would
Here I even placed NPC’s ontop of the vehicle and it doesn’t cause the behavior, it definitely is caused by players.
What happens if you make the part smaller, and increase it’s weight and friction?
Ah okay nevermind then.
Edit: I had some issues with players too. Once players would stand on a certain platform I created, it was supposed to move (I added springs) but it just glitched out. Normal parts would work just fine… No scripts were involved.
Does it react different with stiffer suspension?
So car move weird when humanoid is on top, it should be a Roblox error maybe?
I am not 100% sure on that, but it could be the reason!
Yes, but, don’t you have a script in the vehicle that changes the humanoid in a certain way?
I don’t know.
I have a part in my script that makes the players hats invisible when they get on the car, but apart from that there is nothing else that changes the humanoid.
try apart of that script, maybe it fix
When a character is standing/moving around on your vehicle, they apply an equal and opposite force on the vehicle as well. This will have a similar effect as having a “BodyForce” applied down on the points your character are standing. If your car is light enough its possible for the characters to push on the car a bit.
How heavy are you cars?
Some car games I play have this issue where you would jump on a car a couple times and it would start to glitch out, probably a similar thing.
I still think it has to do with the springs. My most recent project, which I even made a post on, was a weight measuring device.
It used four springs. Perfectly balanced. If I would drop a block on it the platform would go down a bit and then stop.
However, when I would stand on the platform, it would go down, stay down for about half a second, and go up slightly.
Making the springs stiffer might change something.
Here is how I get it:
The car’s mass customphysicalproperties is this:
The car’s mass part is this red part:
I do this so other parts in the car doesn’t cause an imbalance of its weight. Each wheel have a mass of 1 because through some testing I figured out that if you make your wheels too light, you wont get any traction to the floor and the car will not turn
Prob a Roblox error, you can ignore it like others games I think.
I can’t really ignore it because in my game players will be able to jump on the cars and it will disrupt the driver. It might even cause the car to glitch out, and it could be abused easily.
If anyone is wondering, this is a custom built car system, I am not using other prebuilt systems like ‘a-chassis’ for example.
Yes, I was playing it and it surprised me, I like that you added that when turning the turn signals turn on. Gw
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Your car is probably over constrained, causing the simulator to go crazy.
If your car really is mass 213 and your wheels are mass 1, you have a really high mass ratio. Putting players on top of the car exacerbates it by making it even more massive. Have you tried bringing your wheels a little closer to the chassis’s weight? In fact I would suggest you increase the density of your car parts overall.
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Here I resized the mass part to fit the actual size of the car
Causes the same behavior
Here I lowered the weight of the car:
Doesn’t change anything 
If I change the mass of the wheels, the car will have trouble trying to move the wheels as the cars torque will be too low for it to move the wheels.
I don’t think changing the mass of the car/wheels will affect it as in my previous post you can see that NPC’s with their own humanoid don’t cause this issue with the vehicle, only players cause this.
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Unless you really need those collisions, you can just filter out regular players colliding with vehicles with collision groups.
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Assembly Mass for your first “repro” is still 213 In the second video its only 162. If your wheels try have mass of only 1 you are still going to have issues.
A mass ratio of 1 to 162 and the mass ratio of 1 to 213 are still going to be too high. Bringing them closer to 1 to 10 or 1 to 20. NPCs standing on your car don’t have the same behavior because they are probably owned by the same person and do some extra NPC-specific optimizations.
I imagine if you call SetNetworkOwner(nil) on the NPCs you will see the same problem.
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It is fixed now!
I did not know having a large difference between density ratios could cause this!
Thank you!!!
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