When building a crawler you want your tires to be soft enough to grip the rocks, but still support the weight of the truck. There are several ways to modify the foams to do this… cut the foam in half, pie cut the foams, or do a star pattern as I am going to show. For me, this method yields the best results.
The first step is to use a marker and divide the foam in to 4 even sections.
Then 8...
Then 16.…
And finally 32...
Then mark a circle about ¼ to ½ up the side of the foam.
Then with a sharp pair of scissors, cut from the outside edge of 1 line to the inner diameter (you drew) on the next line over. Then from the next line back down to a point with the previous cut.
It should look like this…
Do this all the way around and it will look like this…
And you will have this left over.
This takes a bit of time, but will give you the extra bite on the rocks you need.[8D]