How to work out gears i.e. if i've got a 39 x 29 what does that give me? And I run a campag triple with 30 - 42 - 52 chainset, is it possible to get comparable gears using a double chainset? I've been told that using a 10s double with 'compact' rings(??) I should get close to the ratios on my triple. Enlightenment required. Thanks

The campag website has a gear inch calculator, allowing you to enter chainring & sprocket sizes, and wheel size, to give comparison charts between the most typical combinations.

I found going from a 39x38 to a 30x23 that I actually have a slightly lower gear, but with smaller jumps in ratio throughout the range, as opposed to the big jumps on the 13-28 cassette.

do you mean you've got a triple? Or a double with a 38 on the back? Confused.

david, to work out your gear in inches then you need to do (chainring/rear sprocket) multiplied by 26.4 (which is the wheel diameter in inches for a 700x23c tyre

ie (53/15)x 26.4=93.28.
this is the standard uk way of stating gear sizes and relates to an ordinary (penny farthing) with a wheel of that diameter, ie with a wheel of 80inches = 80inch gear.
if this mumbo jumbo doesn't make sense try this:
http://www.sheldonbrown.com/gain.html

http://www.fixedwheel.co.uk/tech.htm