Hi again,

First i use a reference image "View, Image and i add the one in the picture shown"



I like this one because i got a good reference for a tire profile and the Rim that will go with it (love the way Moi deal with image where i can move it anywhere).

I use the Draw curve freeform. Depending on the detail or accuracy i go with Throught Points or Sketch. Click on Show pts to set the freeform to fit the profile and add/delete points in the process.



I now do a revolve and see how it looks. But somewhere around a small part at the bottom right, i will Trim the curve and keep everything so i can use the Contruct, Curve, project, that will do it on 1 x part of the object and not on all available face in the view. (except maybe at the bottom but that one can be deleted). I do this for the thread. Draw my own or use another image for reference.

Again for the Thread i use the Draw Curve, freeform (throught points or sketch) and the Line, Polyline. (again using the mirror and anything available to get the result wanted).

The problem i got when i do the projection and use the extrude, i dont get both side caps, i think it might be because of the curves, i have to do network to close them.

I think it is better to create the overall pieces then use the boolean operation to make the dent or break in the form.



Final look then back to the drawing board for my technic.



Carrara Render