Algodoo

Hmm... It looks like there is a problem with the suspension. I have a feeling it might be that purple rear suspension bar. Or, it might be the hinge motor that makes the wheels turn. I really don't know much, but I'm pretty sure that it's something to do with the suspension. I fiddled with the suspension a bit, and I figured that if you put the suspension like this:

Front: Spring constant: 20500 Damping: 2.000 Target length: 1.15

Rear: Spring constant: 27000 Damping: 2.000 Target length: 1.25

That doesn't fix it, but it allows you to go at higher speeds before it happens. Btw, have you seen my new working firework? I just uploaded it. OT: Nice job on the car man, 10/10, it's very detailed.

Okay, I'm pretty sure this is what happens:

The purple rear suspension bar with the hinge fixed to it; when the suspension flexes, it makes the hinge go CrAzY. If you're thinking it's a flat track, it doesn't make the suspension flex, that's because the weight of the wheel compresses the spring, making the purple rear suspension bar move, then it makes the wheel do that. If you're thinking it's rear wheel drive, why is it happening to both wheels, it's because when the back wheel hits the ground in that jumping movement, it makes the front wheel jump too because the front wheel is already on the ground. I hope this helps.

The wheels are polygons, change them to circles to fix the problem.

edit: go to the car's wheel hinge ,set legacyMode into 0(at script menu).

Thank you very much I've fixed the problem .

your welcome ,actually the solution is came from kilinich. you must thanked him, not me .