you could increase the spring length in the car file code.
Edit the
maxSuspensionTravel in the cars .car file: (increase the number to say 0.2)
SUSPENSION damperAmt | springAmt | targetValue |
maxSuspensionTravelHere is a doc that shows what each section does.
http://www.chi-ad.com/DokuWiki/doku.php/english_manual:res_vehiclesetupThis may change the cars driving habits though
As with real vehicles, you have to set cars up to work on the surfaces you wish to drive on