Hi Otimo,
Welcome to the forum!
You might want to raise the front of the car up off the ground and rotate each wheel by hand to check if you see any sideways or in/out movement, it could be a bent wheel.
Check also the wheel bearings by grabbing the tire and try moving the wheel side to side.
There should not be any play or clunking sound.
If you're close enough to AutoPoint Motors in Pt. Richmond they can check it for you and pre-tech your car. You can get tech at Infineon but it'll cost more.
Here's the form:
http://www.nasaproracing.com/images/rule...s/form_hpde_tech.pdf
Since you must have already register because hpde1/2 is full just come on out and play.
I can save a space for you in our pit area.