[ODE] Real contact forces (=weight distribution)

[tt]

Hi

I have a 6 wheeled vehicle with a passive suspension mechanism modeled 
in ODE and I'd like to find the force distribution on each wheel to get 
the normal forces at the contact and use them in a special wheel-ground 
interaction model. Unfortunately, the contact forces available in ODE 
are not what I'm looking for since they may be bigger or smaller than 
the real weight on this contact due to the use of constraint modeling.
Does anybody have a solution to this problem? I didn't find anything in 
the old postings, but saw that approx. 1 year ago somebody was trying to 
implement pressure sensors on the feet of a walking robot, which seems 
to cause the same problem.

Thanks for your help.

pura vida,
Thomas