sprocket ratio theory

[sofadriver]

Theoretically, when trying to attain higher road speed, is it better to use a larger sprocket in front or a smaller in back? Will one require more horsepower than the other to maintain the same road speed?

[Dirty Duc]

Given unlimited horspower, either larger in front or smaller in back... or both.  15/43 is approximately the same as 14/40 as I understand it.  Which one you modify does not matter from a speed standpoint.

However, wind resistance goes up with the square of the speed so you might find that a lower (numerically higher) gear ratio gives a better top speed depending on the hp of the bike.  If you can't reach the rev limiter in top gear, you are leaving speed on the table and need to either fit a smaller front or a larger rear.

**edited for clarity

[Slide Panda]

You can hash ratios here:
http://www.gearingcommander.com/

[sofadriver]

Thanks guys.  That calculator looks like it will help