Story

In this digital universe, where the very air is electifying, The User found a way to gather energy for procedural fixed programs (read inanimate). But... we Programs could not utilize it. The tails you see behind the bikes are pure solid energy. Engines are made of three major components, The "Contrivier" creates energy (Still working on how), utilized by "Motors" to keep the bikes moving, and a "Stymier"(I am sure I can find a better name for this) which will solidify the rest and push it out (Practically creating the 'Trail'). The engines produce more than to run the bikes but have to dissipate the rest instantly in a certain fashion so as not to overheat the themselves, hence, the energy trails. A "Boost" (somewhat like nitrous) will utilize more of the energy making the tails shorter, but this can be done only for a short while because the motors heat up. The bikes are equiped to harness the energy of some other bikes energy tail, but it is an extremly risky proposition, your bike should graze the other guy's tail. Grazzing would in effect will add to your engines output hence not much use so your engine will funnel this "extra" to the Stymier, effectively making your tail longer or help you go to higher speed (boost) without shortning your own tail.

Better engines might be able to utilize more of the energy harnessed effectively increasing your speed, or maybe able to sustain the boost for longer period.