What is the best way to model a flat tire? What I have are the "rubber-vinyl" tires. thanks, John.

You could try melting it with an iron (using a suitable barrier to prevent molten vinyl from ruining the iron). Or cut away the part you want to be flat and making the squished part from epoxy putty.

You could try a flat iron , turn it on turn it up side down put a piece of paper on top and try melting the tire . Experiment first with the temperature setting and scraps before jumping in head first .