ghukins
Member
Weight has very little bearing on speed; it mostly has an effect on acceleration. Overcoming aerodynamic drag is far more important. This is why time trail bikes have aero frames, wheels, and handlebars. A TT bike weighs more but goes faster. That aside, no one is making road e-bikes that can reach 30 mph with assistance; they are all restricted, usually to a mere 15 mph. But given that a strong cyclist can maintain 25 mph+ without a motor (when I was young, I time-trailed at a consistent 28 mph), a small motor could certainly help a rider go faster.
In the US, you can get a Trek Domane e+ with a Bosch motor that provides assist up to 28 mph. Fats and sleek bikes, but at 28 mph, as expected, the battery goes away fairly quickly. For 2020, the Domane will come with either a gen 4 Bosch motor, good for 28 mph, or a Fazua drive version - good for 20 mph!