How to make flat tires

[Chevy II]

I tried heating up the tire with a heat gun, then pressing the tire down on the counter while I had a wooden dowel inside the tire. The tire looks flat, but the wheel opening becomes a little oval and doesn’t fit the wheel properly. 
Any suggestions on other methods or tell me what I may be doing wrong. 

[DJMar]

I don't heat up the whole tire, just the part I'm going to flatten. This works best on solid vinyl tires, although I have done it on hollow vinyl as well.

I actually use an old iron for this. Low heat, gentle pressure, until the tire is where you want it. If you're worried about using the household iron, you can cover the heating surface with some tinfoil.

[64SS350]

I found this on Pinterest awhile back...

 

[ncbuckeye67]

That looks amazing! I may have to try this.