Rim and Hubcap
The easiest way to make the rim is to create a cross-section curve and then lathe it around an axis. Create a new file called "tire.max." In the top viewport, create the curve shown below.
Now create this second curve for the hub cap:
For each curve, add a lathe modifier and then add a Meshsmooth on top to create the rim and hubcap. Under the lathe modifier, change the number of segments to 24 or more so that you only need to use 1 iteration in the Meshsmooth to conserve polys. Also make sure that you are lathing along the x-axis by clicking the button labeled, "X" under "Direction" and also make sure you click the "Max" button under "Align". You will also have to position the lathe axis for the rim, simply do this by expanding the lathe modifier and clicking on the "Axis" part of the modifier and then dragging the axis in the viewport. Both the rim and the hubcap should have their axes in the same position. After all that, you should have this:
Tire Rubber and Treads
The first part of the tire, the rim and hub cap, were relatively easy. This part is a tiny bit more complicated depending on how you do it. The way I chose to do it is similar to the way that Thomas Suurland
did his treads on his website. The actual pattern of the treads is up to you because all my references have different tread patterns so it's not really a big issue what they look like. Put your polymodeling skills to work and create something like the image below. You should set it up so that it can interlock with a copy of itself at the back and at the front.
Now you have to make an array of these objects and then attach them all together and weld vertices between them. To make an array, select the object and then under the "Tools" menu select "Array." The settings I used are shown below but yours will probably be a little different. I duplicated it 50 times. The number of copies will determine the radius of the tire. You have to use settings that will make them sit nicely next to each other with no spaces. The next step is to attach all the pieces into one piece and weld vertices between them. This is the most boring part of this tutorial because there are a crapload of vertices to weld! If you are feeling brave, you can use a "Vertex Weld" modifier to automatically do the welding for you but you have to make sure you have the right setting or you will get the wrong results. This process uses a hell of a lot of polys but if you want the tires to look realistic, it's better this way. You could also use a bump map or a displacement map if you are not planning to have close-ups of the wheels.
Now you need to add a bend modifier to the tire strip to make it circular. Set the angle to 360 degrees and it should make a perfect circle.
Now merge the file with the rim and hub cap into this file and scale them as needed to so that they are the right size. Now hide the tread and then create a curve as shown below. It's rather untidy but doesn't need to be perfect. Now lathe it making sure that the axis is in the same place as the axis of the rim so that it fits perfectly on the rim as in the second pic below. Add a Meshsmooth to it.
Now unhide the tread and position it on the tire. You might have to scale it and make it a little narrower but after that you should have something like this:
The last part of the tire is the air valve tube which is easy to make with a cylinder primitive and a bend modifier. Just create a simple one with a cap that looks a little something like the image below and the position it in the tire:
Well now the tire is done, all you have to do is merge it with the file containing the car and then make instances of the tire and place them in the correct positions.
Well the exterior of the car is complete now. All that's left is the interior. With the skills you have picked up from this tutorial, that should be easy for you.
Proceed to the next chapter: Making the Interior.