I purchased a brand new pair of Sparwoods for my Cutthroat.  The previous Thunderburts were set up tubeless, so I thought I would do the same with my new Sparwoods.  At about 30-40psi, the tire exploded off the rim, covering me, the walls, floor, and ceiling with sealant.  Thinking it was a fluke, I tried it again.  Same result.  Covered in sealant, ears ringing.  At this point I'm gunshy.  So, last night I decided to just throw a tube in them so I could at least get my bike back into commission.  At 40psi, the tire launches off of the rim and the tube explodes.  Big bruise on my leg.  I've changed countless tires, and I've had different types of flats, but I've never had it where the tire actually explodes right off the rim.  And after 3 times, both with and without tube, I have to say I'm pretty leery of trying again.  If I can even get the tire to stay on, I don't know that I want to bounce around gravel roads and take corners on pavement.  There has to be some kind of manufacturing defect.  I'm perplexed.