Miller2

Right now I am riding a 30/42/52 105 9 spd setup. My LBS has indicated that my middle ring needs replacing and they suggested I try a 39 ring instead. Since I had inquired about a double setup, they thought this would be a good way to get the feel for a double, effectively eliminating the need to use the small ring....more or less. My cassette is a SRAM 12/26.

Will this produce a reasonable replication of a double setup?

monogodo

Both of my double setups are 53/39, so yes, it is a reasonable replication of a double setup.

Carbonfiberboy 

Here's another thing to think about. Calculate your gear-inches for each gear in your present setup. A spreadsheet works well for this. If you don't already know, you divide the number of teeth on a rear cog into the number of teeth on a chainring and multiply by 27". Do that for all your gears. That gives you the size of the front wheel on an equivalent "ordinary." More importantly, it gives you a figure for how "low" or "high" a gear is.

Now, you can put them in mental order, lowest to highest. You'll notice that some of them are almost the same. Also notice how close together the gear-inches are that you get for the 30 chainring. Now copy that series to a different spot on the spreadsheet and change that 42 for a 39 and see what happens to the gear-inches and where the different gears fall in order now. You can also experiment with different rear clusters, and compare the gear-inches that you get.

The bottom line of what I'm saying is that the main benefit of a triple is that it gives you a lot of gears close together down in the lower ranges. If you do a lot of big climbs where you use the inner ring with various rear cogs, you might not be as happy with a double. If not, then why not get rid of it and save the weight.

BTW, I wear out a middle ring about every second or third chain, just because that 42 is so versatile that I seldom change out of it.