Tony Hadland’s book the Moulton Bicycle includes the comparative testing of full sized wheels and small 16 inch ones using identical pressure and tire type. These lengthy tests led to the Moulton view of small wheels listed in their Q&A section quoted below:
1. Why the small wheels?
The small wheels are an essential feature of the Moulton concept. They offer many advantages.
With only half the rotating mass of the wheels on a ‘conventional’ bicycle, it is possible to accelerate faster.
They are extremely stiff and much stronger than larger wheels because of the short spokes.
The aerodynamic drag is lower; there is less frontal area and less spoke area causing turbulence to slow you down.
The centre of gravity is lowered, resulting in improved stability.
The small wheels free up space normally occupied by large wheels, allowing luggage to be carried lower.
2. Aren’t smaller wheels harder to pedal?
The gears are chosen so that they correspond to pedalling a bicycle with large wheels.
The smaller frontal area results in less aerodynamic drag.
The lower inertia means that you can accelerate faster.
If you are still doubtful, consider the HPVs (Human Powered Vehicles) developed for the ultimate performance - many of these use the unique 17" Moulton wheels and tyres fitted to the AM series bicycles.
3. Why the space frame?
The construction makes it far stiffer and stronger than conventional frames.
The weight is similar to that of the best conventional touring bicycles - and the Speed model is comparable with the lightest racing frames. In conjunction with the small wheels it results in a low centre of gravity.
The standard frame size can be ridden by cyclists of almost any size.
The low top tube leads to improved safety and controllability.
The low top tube allows it to be ridden equally easily by men and women; it is also a major advantage for elderly or disabled riders, who cannot easily ride conventional bicycles.
4. Why suspension?
It allows the advantages of the very rigid small wheels, high pressure tyres and space frame to be enjoyed while giving a much more comfortable ride than a conventional large-wheeled bicycle. The road shocks experienced on a conventional bicycle are dramatically reduced.
It is a light, simple, maintenance free system.
Improved traction - the wheels do not bounce going through corners or on rough surfaces.
Reduced strain on the wheels - the wheels stay true, spoke nipples stay tight and spoke breakages are extremely rare.
5. Does it fold?
No - this is a no-compromise high-performance bike, quite unlike any folding bicycle.
The frame does separate into two parts.
This does not affect the frame rigidity - tests on a brazed-up version of the frame against the normal separable version showed no difference in rigidity. When separated into the two parts, it easily fits into the boot of a car.
When placed in the carry bag, it can be carried on a train as hand luggage, rather than needing to be placed in the luggage van of the train - a big advantage given the restrictions on some train services. Users have also transported their AMs as normal luggage on aircraft flights.
6. Is it as good as a conventional bicycle?
It’s not just as good as a conventional bicycle, it’s better:-
Owners of Moulton bicycles report that after using the Moulton for a week, they never want to ride conventional bicycles again. Just look at the specification and the performance details.
7. How well does it perform?
An AM bicycle holds the world speed record for bicycles of conventional riding position at 51mph, fully faired.
The AM bicycle has successfully completed the Race Across America (RAAM) - finishing the course of 3117 miles in 10 days 15 hours and 1 minute. Owners of AM bicycles use them successfully for commuting, touring the world and for racing. The APB bicycles are ideal for commuting, touring and use off-road.
My own real world experience over 20 years of owning several F frame Moultons, an ATB and a Mark 3 seems to confirm at least equal rolling resistance. I do also confess to riding and owning full size bicycles-a touring bike and a mountain and road tandem.