Have been looking through my patches and found this one from last year
The implementation is incomplete: Fixed skid mark width. No surface type dependency. Depends on tire squeal value. Should eventually depend on tire temperature(which we don't have)?
I've pushed the code into a skid marks branch:
https://github.com/VDrift/vdrift/tree/skidmarks
Please checkout and report what you think. Don't forget to pull vdrift-data for the skid mark texture
For windows users there is a binary against vdrift-2011-09-01:
https://sourceforge.net/projects/vdrift/...skidmarks/