Trek 520 gears

cath mack said:

I have recently purchased a TREK 520 touring bike but the chainset which is a Shimano 105 52-42-30 (9 speed) does not provide a low enough gearing with the 11-30 cassette.

I need to change this for something which gives lower gears - I would like to go down to about 20" gearing.

What chainset should I go for and what needs to be taken into consideration. I find I dont use the 52 cog at all - I dont need that kind of speed and dont have the power to keep it spinning

You can get replacement chainrings for that crankset that will lower your gearing range. Perhaps a 48/38/24 (or 26) would work better for you. 24/30 would give you 21.6 gear inches. TA is one brand that makes chainrings that would fit that crankset and are available in the US. Another alternative to get low would be to use a mountain bike triple in 44/32/22 or similar configuration. Contact your LBS for help or search online for suppliers. Chainring switch is something you can do yourself.

cath mack said:

I have recently purchased a TREK 520 touring bike but the chainset which is a Shimano 105 52-42-30 (9 speed) does not provide a low enough gearing with the 11-30 cassette.

I need to change this for something which gives lower gears - I would like to go down to about 20" gearing.

What chainset should I go for and what needs to be taken into consideration. I find I dont use the 52 cog at all - I dont need that kind of speed and dont have the power to keep it spinning

You met with a very common issue on many of today's touring bicycles. Trek's 520 has gearing for powerful riders who are light and carry no load or a light load. You really can use a new Mountain Crank with a "matching" Mountain front derailer. You will need to shorten the chain to remove some of the slack.
http://bike.shimano.com/catalog/cycle/products/component.jsp?PRODUCT%3C%3Eprd_id=845524441762860&FOLDER%3C%3Efolder_id=2534374302032784&ASSORTMENT%3C%3East_id=1408474395181202&bmUID=1131374686282
http://bike.shimano.com/catalog/cycle/products/component.jsp?PRODUCT%3C%3Eprd_id=845524441762909&FOLDER%3C%3Efolder_id=2534374302032785&ASSORTMENT%3C%3East_id=1408474395181202&bmUID=1131374686282
Shimano LX 580 44-32-22T
series or something like them make good sense, but the cost to swap components is significant.
A front derailer that is designed to work with the front crank/chainrings really does make sense.