Hey everyone. I got a little question to ask "the experts"

Im riding my track bike with a 42 tooth up front and a 16 tooth in the back. Me starting out from a stop light is fine, but me speeding down the road, I find myself, as what Ive heard other people refer to, as "spinning." Im pedaling real fast and not really get any more speed. I WAS running a 42/18, but went down to now a 16.

Do I just need to go to a 14 or 15 tooth? or maybe put on the 52 tooth that came with the crank? Im not that knowledgeable when it comes to gears.

I live in an urban city with a few hills.

Any help would be great. Thanks.