it works, you are right, thanks a lot !
in fact my real problem was a little bit more complex
I wanted to turn a car wheel on y and z
I needed your fix object pivot but it was not enough
I just found the solution of my problem. it is exactly:
rotate object i,0,0,0 // re-init rotation
zrotate object i,wheel_angle // first, wheel turn on itself
fix object pivot i
yrotate object i,car_angle+steer_angle // wheel orientation on the road
zrotate object i,0 // this magic line was missing to keep my wheel vertical after the first zrotate...
thanks a lot for your help with fix object pivot which missing !