Adjusting gear ratio I currently ride a single-speed converted bike (vertical drop-outs). I like the ride but feel that when I'm going for high speed on the road, I'm pedaling too much. Currently running a 18T cog on the rear and 42T on the crank, with a 2.333' ratio.

I'd like to increase the ratio and have a cassette on the rear hub, with a 16T cog. I'm wondering what's the best way of switching the chain to the 16T and keeping the chain tensioned.

Would it be as simple as removing one link from the chain or would the tension not be there?

As the 16T is one level down in the cassette from the 18T would the chain line be OK?

Thanks in advance for any advice.

EDIT: Here's a picture of the gearing setup to make it clearer:
If you poke around on the web enough, you'll find a "magical" gear ratio calculator somewhere. You input the length from BB to dropout and it spits out the 
front/back combos that will work w/o a tensioner. 

Try this one. 

http://eehouse.org/fixin/fixmeup.php

It would be much simpler to change the front chainring, if you can find a magical
combo that matches what you want for a gear. There are also "half links" available that allow you to tweak the chain by less than a full 1 inch link pair. 

FWIW, a single speed bike means your almost always in the "wrong" gear. Any change you make will only change when you're in the wrong gear, not the amount of time you spend in the wrong gear. If you're not happy being in the wrong gear, just buy a derailler and a shifter.