maybe here is a solution !
http://www.sketchucation.com/forums/scf/viewtopic.php?f=61&t=9586
Stoff

Maybe this one can help:
http://de.youtube.com/watch?v=PzOSwaUp_gc&feature=channel

Regards, Stoff

I made a model using a skydome:
http://sketchup.google.com/3dwarehouse/details?mid=a1ef1720d22e9898a380d72272f0b71f

More models you can find in the 3DWarehouse by searching: " sky dome "

Regards, Stoff

Hello Pilou,
your wheels are no cylinders !!
http://sketchyphysicstutorial.googlepages.com/
http://sketchup.google.com/3dwarehouse/details?mid=5cde5f472d011a8de5e98147217ea8c1&prevstart=0

Stoff

here is a working model:
http://sketchup.google.com/3dwarehouse/details?mid=519f4e610101a152cb92776bc5cf0558

Stoff

Hi dolf,
many thanks for your GREAT analysis !!
after editing ControlPanel.rb everything works perfect !!

Stoff .......... ( search in 3DWarehouse for my SKPhyModels )

Hi !
I have the same problem only on my notebook ( Vista !! ) and no solution !?

Hello, you should try to increase the worldscale in Physics Settings, e.g. 20, then it works as expecetd.