Solid Inner Tubes
I haven't tried the solid inner tubes but have tried the airless solid tires and that was within the last two years so I suspect the technology was fairly current. The ride was very bumpy and chattery compared to air tires and I felt that the weight/rolling resistance cost about one to two gears, meaning I had to drop down in gear on equivalent routes compared to normal tires. When I finally gave up after a few months, I really did notice the difference. They also seemed to wear more rapidly. Tires were the 700 size, about 1 inch wide.