Board Thread:General Discussion/@comment-25819077-20150121210329/@comment-25819077-20150122135024

Evtini200 wrote: I have my own theory about Sonic's speed.

The rings are his main power source for speed. His boost gaugue fills up when he collects them and when he boosts (using the collected ring power) he acttracts more rings. Kinda like how the Chaos Emerald's energies attract each other (and it was stated in the comic at least that rings where a byproduct of the Chaos Emeralds so it would make sense that they'd share the same properties).

Stuff this also explains:

Why rings appear in a straight line.

Why rings disappear when he collects them.

How Sonic can use Light Dash without gear.

There are holes to this theory, but that's what I got for now.

As monkey said, he was faster before boost, and he will remain fast after (actually, considering that Sonic Team makes the games, maybe not).