chainrings
 

Hi, first, i live in México if somes word are not write correctly is for my english.
I have a trek bike (8000) with Icon Graphites Series crank set, i need to change th rings and i don't know what brand of ring fits with this crank.

I am grateful for your help.

If I recall, Icon rings are compatible with Shimano compact rings.

You need to know the diameter of the bolt circle.
For Shimano double chainsets this is 130mm which is fairly standard and available from many other companies.
Campagnolo rings are 135mm.
You can get rings with 110mm bolt circle, usually for smaller sized rings.

If your chainrings are 130mm, then any 130mm will fit but you should try to get one compatable with your trasmission/chain type. All the big mail-order/internet shops (such as performance) do chainrings.

From Branfordbike (without permission) :(

Chainrings are most often measured in reference to their Bolt Circle Diameter (BCD) depicted as B in the above picture. BCD is literally the diameter of an imaginary circle that connects the centers of all the chainring bolts.
It is easier to measure the distance between adjoining chainring bolts as depicted by A in the above picture. Use the chart below to determine what size rings you have.

74 BCD Rings: A = 43.5 mm, B = 74 mm
130 BCD Rings: A = 76.4 mm, B = 130 mm
135 BCD Rings: A = 79.5 mm, B = 135 mm
144 BCD Rings: A = 84.6 mm, B = 144 mm

And a different cartoon is needed for a 4 arm bolt pattern.

in fact it's BCD and Pattern that matters.