thank you very much marco!

it works now! all i had to change was the order of the entities in the wheel constraint definition... now i am ready for some more experiments!

i still don't know what the spring/damper constant specifies?

if i want to have shocks / suspension, do i have to use an additional slider constraint for each wheel? and how would i set this constrain up so that it works like a spring? just set a motor for the slider which is active all the time?