I’m currently working on a car system, and the car seemingly jitters around when driving it. I’m trying to work on the car so that it drives smoothly.
I’ve tried to use springs, but I’m not sure if I’m using them correctly.
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Ok ive never used springs before but ill still try to help.
Mabye increase the “Stiffness” property
or just in general mess around with all the properties
There are a LOT of similar posts to this (and I’ve posted in quite a few of them).
Try using the Search tool up top with the term “car jittering”, or “car bounces”, or “car suspension” for ways to troubleshoot your issue. 
That’s interesting, because I haven’t been able to find one. Could you link me to one please?
In that 2nd picture your springs are way too stretched.
I already did. There’s a Search tool up top. I used the term “car jittering” and got a few hits.
From the video it looks like your wheels may not be round. Do you use MeshParts, transparent Cylinders, or Ball Parts?
Tuning a Roblox car is like real life. Every time you make an adjustment on one parameter it can affect all the others, so you have to keep fine tuning it.
Factors that can affect this are.
Wheel Density.
Car Mass.
Wheel shape (not round).
Spring damping, and all the length factors.
Unreal MotorMaxAcceleration values for HIngeConstraints. Wheels that accelerate too quickly aren’t realistic and cause traction/bouncing issues.
MotorMaxTorque values that are too high.
The wheels contacting the car Parts.
I’ve covered all of those topics and more on some of the other posts I’ve done. Please try searching using a few different terms and I’ll almost guarantee you’ll find a solved post with helpful information.
Most of the time the wheels are not perfectly centered or not perfectly spaced.
Take the whole car and move it to 0,Y,0 whatever you need for Y. Then you can look at the right side vs the left side and they should be the same … other than one number will be a negative.
And you can also select your Wheel Parts and find where the Attachment is located for the HingeConstraint. It should be at 0,0,0 for the one in the CanCollide wheel.
Ya I go through everything and match it up. Also I’m sure you know the steering rods need to be orange and not red. Looking at that second picture of the shock springs you can see they are very short, so they are stretched out … you can even see the blue arrow showing how far that is off.
@barugas As it’s rolling along look at the wheels from the side … if they are not spinning perfectly … then the wheels are off. (this looks to be the problem)
To be fair, I’ve been playing around a little with the attachments and properties of the motor, and I’ve managed to kind of negate the amount of bouncing, however not fully. I believe it may be due to the fact that I am using meshparts, and it’s not fully circular.
The standard Roblox approach is to use invisible basic Cylinder Parts for the actual collidable wheels, and just weld your visible MeshParts to them with CanCollide = false for those. Roblox’s physics engine handles default Cylinder parts with special case code that treats them as perfect cylinders. This is more smooth and reliable than even using higher-polycount meshes with PreciseConvexDecomp collision fidelity, and much better for performance than upping your render meshes’ fidelity.
In addition to fine tuning the spring constraints, you’ll also want to use Part.CustomPhysicalProperties on the invisible parts to make sure that the parts connected to the same constraint (e.g. Part0 and Part1 of the same HingeConstraint) are on the same order of magnitude of total mass. Physics solvers can get very jittery when you have high-mass parts connected to low-mass parts via constraints. This is an important part of Roblox vehicle building that often goes overlooked. The right spring stiffness, damping, and freelength combination cannot solve a mass imbalance problem.
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