Roundtail

Tortola Roundtail

A crazy looking bike, but with purpose.  It is fun that the frame circle almost matches the wheels, but there is more to it than ascetics.  The giant circle is essentially a leaf spring.
The initial reaction to riding it is that no noticeable difference in ride quality is felt.  The real benefit is on longer rides when the micro-shock from tiny bumps in the road would normally start to agitate the rider.  After about 2-3 hours in the saddle the rider will start to appreciate the comfort of the Roundtail.  After the initial ride the effects are noticeable even at the start of a ride.
It does have a small suspension effect.  The rider notices bumps that are usually uncomfortable are now much smoother.  Test riders noted that they were looking for instead of avoiding bumps just to feel the action of the frame.
The frame is designe on CAD where finite element analysis can be studied.  The frame not only smooths out the bumps, but dampens the high frequency vibrations, the ones that can feel like holding a power sander.   Durability of the frame is improved since strain is transferred around the circle and not on any one specific point as a triangle would have.
Frame testing beats it up with 100,000 cycles, and the Roundtail surpasses a traditional frame.

I got the chance to ride this bike for a few days.  I had mixed feelings about it.  While it does ride very nicely, there are those shortcomings that I cannot do without personally.  The biggie is that the 2nd bottle cage mount on the would-be seat tube is missing, leaving only one mount, thus one bottle.  The next, and much lesser, is that there is extra material in making the rear round, so there is a weight trade off for your comfort ride.  This really is not a problem for the intended end user who does not intend to enter competitive racing.
I like the frame and the ride quality, but coming from a mountain bike background I feel that smoothing out road bumps pales in comparison to what happens off road.
A much better application of this technology would be in a hard-tail mountain bike frame where there is a greater need for smoothing out the bumps.
It's not for me.  I need two bottles on my road rides, and am not willing to give that up for creature comforts, but if you are looking for a cool frame that rides excellent, the Roundtail might be for you.