Can't get wheels into rfactor

[nothke]

When I export wheels to rfactor, and get on the track, game crashes..

This is what I did...

1. Exported all 4 wheels (as separate objects) from 3dsmax in .x format with pivots on the wheel centres.
2. Put them into 3dsimed, edited materials a bit (added specular).. Combined/replaced materials for all wheels so that there is 4 materials (instead of original 16, 4 for each wheel)
3. Exported to .gmt and overwritten then with already existing wheels.

When in game, the wheel models look fine on spinner, but when I try to get in game, it crashes..

What is the problem? Are there some material naming obligations perhaps? Is the problem in .pm file? I don't get the error...