CUstom scar model wheels fall through ground

Hey there. I took a look at the scar editor and I decided to create my own vehicle using the editor. So I managed to import my custom model with its wheel both separated and I rigged the entire model using the scar editor, including lights, exhausts etc… Even spawning the car it works well enough but whenever I drive fast or even nearly at top speed, the wheels get stuck in the ground and they glitch out causing them to get stuck and bounce back up, causing the car to flip. Here is a screenshot : http://postimg.org/image/ep6s2yvgf/full/
Does anyone have any suggestions that could fix this? I’ve tried modifying the suspension and still nothing works…

Thanks