Gary - this "Slime" - is it something you buy in an automotive shop? I'll have to try to find some. Does it leave the tires still with some "pliability" or do they become more stiff? I like pneumatic (air-filled) tires, which my R'n'R'er has front and rear, for rolling smoothly and quietly over most surfaces, but they do lose air too easily.

Thanks,
Jim