Summary

Modeling car tyres is a polygon eating exercise (you end up with quite a few in the end), but definately worth it if you want to make a realistic looking car: using bump maps for threads is a bit too obvious.

Reference and Interpretation

So what tyre will we make. Of course there's only one brand that comes to mind: Pirelli. Once again, any tyre would do... this is all about the concept.

After having a quick look at the Pirelli site (through Google most you find is Pirelli Calendar images... ah what a shame! :) I chose the Pirelli PZero Direzionale tyre:

More than this you don't need as reference. When you look at this tyre you can see the simplicity with which we are dealing: it's a repeating pattern! And this one is symmetric through the middle too so it's even more easy (on my Alfa Romeo SZ I have Pirelli PZero Asymmetrico's... they're as their name suggests asymmetric).

So what part of this tyre are we going to model? Well only the part highlighted in the next image, that will be all! This part we will then mirror (with the Symmetry modifier) and then Array Rotate it (this will be explained in a short while). Having a quick look at the reference image I can guess that there will be around 30 parts (in the Array Rotate) needed to complete the whole tyre. 30 parts for 360 degrees is 12 degrees per part (remember!).

Starting

It's quite obvious that a tyre resembles a tube and therefor it would be logical to start modeling from a sliced tube. Yet we won't. The way I do it, is make a tube as a basis (a sort of background / underlying model) and over it model the thread (only one part) which will be 'glued' on.

So first the underlying tube. Nothing fancy, I just created a tube (1) (100 Radius 1, 90 Radius 2, 70 height, 1 Height Segment) and posistioned it at (0, 0, 0) which will be the basis. After that I applied an MS modifier with 2 iterations (2). This is not good so far, it's way too smooth and thin. So I chamfered some edges and sliced some stuff using Slice Plane (3) to make it more defined and retain its shape after MS (4). All this is just rough modeling, no measuring or thinking but all by feeling.

The Thread

So now that the basis is there, we will start modeling the thread. First some guidance modeling is need to create virtual boundaries and then the actual modeling can be done.

The reference will be a sliced cilinder. So create a new cilinder with a radius of 110 (the rest of the settings, other than the slicing, aren't important) and set the slice from 96 to 84 (12 degrees centered around the middle top, see the previous tutorial). So the part we will model is roughly the size of this cilinder (1 + 2).

We will start out the thread by making a simple box, which will serve as a rough start, give it a height of 35 (half the height of the cilinder) and convert it to an EP. Now move it to the logical position from where we can start modeling (1 + 2).

Delete the innert part of the box (1) and add a Symmetry modifier (2). Now move and rotate the Symmetry gizmo (so in the Symmetry sub-object) so that it mirrors the box, (probably move -35 in the y-direction and rotate 90 degrees in the z-direction from the top view) (3).

Very good. Now we're almost done with laying the basis. Only two more steps to go: adjusting the Pivot Point and the Array Rotating.

Go out of the Symmetry SO and to the side view (1) go to the Hierarchy tab (this is next to the Modifier Tab, at the right top of your screen). Then you should see the Adjust Pivot options. What we will do here is change the Pivot point of the box, so that it can rotate around a different center, namely the center of the tube. Click 'Affect Pivot Only' (2) and move the pivot to (0, 0, 0) (3). Click the 'Affect Pivot Only' button again to go out of the editting.

Only thing left is the Array Rotating. So either click the Array button, use your short-cut to Array or go to 'Tools' > 'Array...'. Array can make copies of your selected object(s), either normal copies, reference copies or instance copies. We will use Instance copies. Instances are object that have a two way information stream between itself and the object from which it was created. So suppose I make one object, instance it and then edit the new one, then the old will change too and vice versa. Very useful.

So set the 1D Count to 30 (remember?), and the z rotation to 12 (360 degrees / 30 parts), Type of Object: Instance and click 'OK'. Excellent, most of the hard work is done now. We have 30 parts which are all identical and remain identical (they're Instanced!), so we once more only have to edit one part and the rest will come along.

I think the rest of the tutorial isn't as important. I will go through it more quickly, since all you have to do now is just edit your original box to make it look like one part of the Pirelli tyre. Only screenshots of what I did to make my thread look the way it did will be shown.

Almost done with the modeling now, mainly smoothing it (by hand, no MS) and making all the parts fit each other is to be done. After I have done that, I unhide all parts (I usually work at one part alone, only the matching I do with three parts (the top center and the one left and right of it)) and test render it:

More detail can be added if you want (I made it very sloppy now), chamfered edges do make it look better but you will get a high poly count. It's one or the other. :)

The following tyre (of my latest model, the Alfa Romeo ES30 / SZ) is made with the same technique, the rim with the technique of the previous tutorial. Only now with some custom made textures added. I am quite proud of it and think it looks quite fancy.

I hope you liked these tutorials and learned something! Happy modeling!