Hi,i'm playing LFS with joystick using both trigger for direction and gaz but i'm still not able to figure it out how to resolve my problem.
The car seem to steer to the left and it's been difficult to keep the car on track at high speed.
Any idea?
Thank you.

Recalibrate your controller in LFS, in the Options/Controls menu. You might want to make a 'deadzone' too.

I cant recommend enough the need for a wheel to play this game. I don't know how you could drive consistently using a joystick. Especially if the stick is looking after both axis.