I run on a hard packed, moist clay, surface. I used 1/10 scale truck, Losi Pink Tapers and Trinity Blue, 1/10 scale truck, hard, foams. I Dremel tooled the foam ID so I had to slightly stretch foam to fit the 1/8 scale wheel without tearing. Once the foams were installed onto the wheels, I slightly rounded the OD of the foam because the 1/8 scale wheel leaves high ridges on the outside edges. If you add the foam tape between the wheel beads like Aaron typed, that last step might not be needed. (Thanks for the tip Aaron.)
I then trimed the tires like KINGKZJ typed. Be sure you trim the ribs, because the tire won't fit into wheel bead groove with them still there. Stretch modfied tires over the installed foams. Make sure the tire is centered all the way around on the wheel/foam before glueing. I used a slow drying CA to attach the tire after sliding the tire into the bead groove of the wheel. This will give you more working time. When done the tire will have a short sidewall and firm sponginess.
The tires work excellent. The buggy is "point and shoot". I was able to increase cornering speed, have better acceleration, and I'm still playing with the steering rate. It almost steers too good. I've heard that they get better as they wear. Have patience though! I was carefull on my first set and it took about 4-4.5 hours. I helped a buddy with his and it took us 3.5 hours. They're worth the time.