I've forgotten to tell you how to make the tire hollow : - select the last point of the extrusion path . Then create a new cross-section ( section menu ) . - select the cross section by clicking on it, and modify its options : uncheck the "fill cross-section" box (always in the section menu . - do the same last thing with the first cross-section . Here it is . I hope i didn't forget anything this time ! :) litst