The simplest way and more convenient way is to Simply go online to the Jenson USA website and order the parts that you're looking for or you can head to their warehouse located in Riverside off of Sycamore Canyon in order the parts directly from the warehouse
Chainrings are based on bcd/bolt center distance/ the distance between bolt holes for mounting in mm... Usuallly 104bcd on mounain bikes for the big and middle ring. 96 for the small ring.. That and tooth count.....Rear cassette are also based on number of cogs/speeds and tooth span. Ie.11-36 You will also need special tools to remove a cassette. A chain whip or Cog pliers to hold the cassette in place and a special key to remove the retaining ring
If you know what came stock on the Trek just order it from the site or on the phone and select or request will call pick up. If you don't know call or email Trek, get the specs then place the order
Set up a will call at the Sycamore Canyon Warehouse
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