This tutorial is intended for you, who wants to learn to model tires like the one I showed first on Alfa Romeo GT. This tutorial is not intended for Blender newbies but for users with some knowledge of using Blender for modelling. For example, you need to know how to create a plan of a given size by yourself.
What you need first
A sketch of the tire, like this one (PIRELLI P6000) :
The dimensions of the tire : let’s use a 205x60r16.
From the dimensions of the tire we guess that :
* The width of the sketch image is 205mm
* The external diameter of the tire is 16inch + 2 * 60mm = 16*25.41+2*60 = 526.56mm
From the image size (in pixels : 500*190), we calculate the height of the image (a part of the tire thread) is 205*190/500 = 77.9 mm
As the diameter of the tire is 526.65mm, its perimeter is 3.14159265 * 526.65 = 1654.52.
So on our tire thread, we can put N times the sketch image with N = 1654.52/77.9 = 21.239. As the image tiles, we need an integer : let’s say our sketch fits 21 times around the tire.
So, we’ll create a 21-edges circle, extrude it to have one face fitting well over the sketch. Next, we’ll model one element (1/21 of the full tire). Multiplying it 21 times, merge, and voila !
Open Blender. Erase all elements of default scene.
In side view (NUMPAD 1), create a circle of 21 vertices. Rotate it to have the bottom edge perfectly horizontal (tip : align top, opposite vertice with the Z axis)
As Blender default circle radius is 1.414 (square root of 2), size it by 0.707 (1/1.414) to have radius to 1.0. Then size it by 0.526/2 = 0.263 (tire radius in meters) and move all vertices up by 0.263 (the radius). It’s OK that the bottom edge is not on Z=0 : we’ll see later why.
Duplicate this bottom edge, separate the duplicated vertices to have another object. Extrude it along Y-axis by 0.205 (the width of our tire). You got a plane and a circle like these :
You can check your work is OK by displaying edges length : you should have 0.205*0.078 for the plane.
One more step and you’re done : duplicate the plane, change one to display only as Wire (Drawtype in Object panel, F7) and select the other one. Enter “UV Face Select” mode, go to UV/Image Editor and load the sketch image.
Return to 3D view and “Object” mode, activate Textured draw type (Alt+ZKEY), you get the following :
The sketch is displayed correctly, without any distortion : the few maths before starting Blender was not useless 🙂
First step of modeling
Select the other plane (the transparent one, without U/V texture). We’ll work on it to model a subpart of the tire thread.
First use symmetry to save you some work : the sketch we have can be split along both X (radial cut) and Y axis (axial cut). So you can subdivide once the plane (in both length and width).
But before you do, PLEASE READ CAREFULLY BELOW !
When splitting your edge along Y axis, no problem. But when splitting along X axis, remember you’re not working on a plane but a section of a cylinder.
That’s why the bottom edge of the circle is not at Z=0. Let’s experiment to get a clue. If you already subdivided the plane, please undo it.
Then cut the face (CTRL+RKEY) at percentage 1.00. Don’t select/deselect anything to keep new vertices selected.
Then, rotate carefully these vertices around Y-axis (RKEY then YKEY) to get them at X=0 (as seen from top or side view) And in side view (NUMPAD1) you can now check that these vertices are almost at Z=0.
Remember this move : when cutting along X axis, do not move edge vertices along X axis, but rotate them around Y axis, to move them around a perfect circle.
Just a little note : you have to move the plane textured with sketch down to get the added vertices above it (so they’re still visible)
Now you can continue with modeling : remove 3/4 of the plane as said above, and cut plane according to each detail visible on thread : you should get something like that :
As you can see, cuts in the plane are mapped on thread details, but for round details, it’s not that yet.
To solve it, just rotate them around Y axis :
This time round details are OK.
As you can see in side view, the tire element is not plane but warped around a circle :
This is why it’s so important to rotate vertices around Y axis instead of translating them along X axis.
Now, we will cut the edges in dark areas, to materialize the hollows of the thread : you should obtain this :
It’s important to keep the edges circling the dark areas ! We will see why later.
Now it’s time to optimize a bit our mesh : we have to remove all unneeded vertices and edges in white zones and on borders. Doing this will allow us to save a lot of polys on the complete tire (remember, we will duplicate this part 2*2*21 = 84 times !!!)
Vertices count goes from 144 to 78, faces count goes from 53 to 22. Good point !
Time to model the hollows !
From the previous step, select all vertices.
Extrude them (EKEY) but without moving them (ESC immediately)
We have to move them to the tire center, but a simple scaling (SKEY) will not do the job : it will act on Y axis, and we don’t want that. Just try by yourself to see why, then undo 🙂
So we have to scale 2 times : first on Z, second on X. Make sure before scaling the 3D cursor is at circle center.
When scaling, I advise you to enter a value with numpad : this way you can enter the same value twice, for Z then for X. A value of 0.99 is a good starting point.
Now make needed faces between extruded vertices, to model the bottom of tire thread. The next image is a work in progress to show you the faces needed :
You get the following once done (seen from under the tire)
Next step is simple : remove faces that interrupt hollows in thread. Look close to this screenshot to find differences with previous one :
Now it’s time to model the side of the tire (i.e. the 60 in 205x60R16)
Start with the external, upper edge of the element, and extrude it without moving it. Scale along X and Z axis (but not Y, as previously).
Work on it to get a rounded side. I advise you to spend some time working on this part, it’s really important for realistic tire :
Save some polys on the side :
You’re almost done !
SpinDup the element you patiently modeled (1 turn, 360ï¿½ of course, 42 steps : because we need 21 elements and the mesh we have is only a half).
Once SpinDup done, you may observe your border vertices are not perfectly one duplicated ones : select all vertices, and remove duplicates (set threshold at 0.001)
You have now to mirror the tire : select row of vertices at the middle of the tire, and move 3D cursor to selection (to have it at tire center, in the middle plane of it) Duplicate the half tire, don’t move it, but rotate it 180ï¿½ in top view (around 3D cursor). Rotate around Y axis to align middle vertices to the ones of the other half tire.
Merge : you’re done !
I advise you to use this mesh with AutoSmooth, to have solid thread details and smooth side.
Here’s some Yafray renders with a rim (black tire material courtesy of Sonix, found in its excellent Car Material Library)