wheel size+gear=speed?

[CDoasis]

Hi,

I'm not sure if this has been posted before, if it has been, I'm sorry.

I have 14" wheels on my vehicle currently, they are stock wheels. I've been thinking about upgrading to 15", 16", or maybe even 17", depending on other factors. However, one of the most important factors (to me) is the gear/speed ratio. Right now, here are the gears/speeds of my vehicle, when at 2,000 rpm.

1st gear: 14 mph
2nd gear: 21 mph
3rd gear: 29 mph
4th gear: 41 mph
5th gear: 51 mph

So if I bought 15, 16, or 17 inch wheels what would the gear/speed ratio be then?

Also, would any of those wheel sizes give me an increase in gas mileage, compared to the 14s I have now?

[CapriRacer]

What you need to do this is the diameter of the TIRES. If done correctly, you won't have any change.

[CDoasis]

Well, the overall diameter of my tires is 25 inches. That should help more.

And I do want to increase size.. I find my current gearing to be kind of annoying, especially when the speed limit is 35 or 55. Plus, I do a decent amount of highway driving so if I had bigger wheels/tires, I would think that that would give me better gas mileage?
Anyway, so I want to go up to 26, 27, or maybe even 28. But I'm not sure how to figure out what the gear/speed ratios would be.

[CapriRacer]

It's simply a ratio.

A 27" diameter tire is 3.8% larger than a 26" tire.

Try this tire calculator:

http://www.1010tires.com/TireSizeCalculator.asp

[98StangGT]

taller tires without any change to gear ratio will give you better gas mileage but less acceleration and vise versa.