Tires work very well on good sized wood, Daniel. I've used as many as 50 to drop both large and long logs, and rounds from height, onto lawns, driveways, pavement patios. Once, I dropped two 400 and 700 board foot fir logs, one after the other, as they were in line, directly onto the length of a sidewalk. This was accomplished with a wood bridge which we built across the walk, laid on logs set lengthwise on either side of the walk, and tires underneath it all. Log truck loaded the first log, then we felled the second. Needless to say, that was a precision fell, with shrubs on either side of the appx 4 foot wide walk.
As Tom said, for repeated rounds being dropped, lashing the tires together works well as does layers of brush alternated with tires...and sometimes plywood on the bottom.
I may lack a skidster and bucket truck, but make do just fine..for 37 years now. Same goes for Tom...and many of us grizzled vets