Modifying Brake Cable to Fit? I have recently decided to replace my brake cables before a particularly long ride, since they haven't been replaced in a number of years.

The problem I have is that the stock rear cable on my bike has an exposed section and, as such, the new cable I have purchased (which has an outer casing running the whole length) will not fit in the groove.

What is my best option? Is there a preferred way to cut the casing on the cable? I.e. should I cut just enough off to pass the obstructions, or should I cut off a long section so the new cable is similar in appearance to the one I am replacing - an elongated exposed section.

Or better yet, are there cables available to purchase which will fit right out of the box?

Thanks in advance!
Cutting cables and housing is a bit of a pain in the ass (especially regular spiral housing for brakes). A Dremel with cutting disc or something like the Park Tool CN-10 is useful to cut the housing, along with a small file / punch to make sure that the hole is clear and smooth. 

The rules for running cables are here and here, along with some directions for cutting. Even if you do get a kit (e.g. this), you will still need to do some cutting, since bikes are of different sizes. Assuming your housings were sized appropriately before though, you just need to use them to size the new ones.  

Note that bad cable installation can drastically degrade performance / be dangerous if its on your brake systems. 

The cable cutting tools may not be a worthy investment if you don't use them often enough, so you may want to borrow them from a bike co-op or just get a shop to do it for you.