Mark also brought a pair of Primo Comet tires to compare. One was a new 16 x 1.5" ( 305x40 ) which while fat is light and supple like the 20" x 2.1" tire he brought last month. The other was a nominal 16" x 1-3/8" ( 349x37) Comet that is actually at least 5 mm different when mounted and looks even more different than that when off the rim. Ya gotta love tire sizing systems!

Mark's Comments; I continue to be very impressed with the 20" x 2.1" tire as a comfortable smooth rolling tire. Even at 40 psi I outcoast everyone I ride with. I may use the 305 and 406 versions on the front and back of my next go-fast bike. It's a question of do I want the stiffer, narrower 349x37 for it's nearly 16.5" rolling diameter, or will the wider, more supple 305-40 roll better despite only a 15" rolling diameter?

You're probably thinking "A 37mm Comet is anything but stiff". True in comparison to almost any other tire, but these new tires are amazing.

BTW The new Comets are rated at 100psi!!!! At 60psi the 2.1 x 20 gave what I consider a harsh ride, on a bike that's quite stiff vertically. Reducing pressure to 40 doesn't seem to have slowed me down. I can only imagine how they would roll at 80psi, on a dual suspended bike.