It's not really the role but my questions - and comments like Mac's... Believe me, Lewis, no-one has really wanted to put your problems and thread off-topic - but you need to be clear when asking and if you cannot be clear (as you may be a beginner not knowing what may be important), at least answer when people want to clarify the situation. (Honestly, we still do not know for sure whether your problem comes from inaccurate use of the SketchyPhysics plugin - no matter how many times I asked you to let us know)

Hi again, I have just done a test and this slightly simpler method should work (in most cases): Right click on the car body and select "Explode" in the pop-up menu. Hold left-shift down and left-click on the roll cage. (All the car body parts and the roll cage should all be highlighted now.) Right-click on one of the selected parts and select "Make group". That should do it and the all the joints should still be functioning correctly if the model is not too complex and does not use ruby codes in the controllers.