Originally Posted by dsafarik
I am a newbie so please forgive my elementary question. What are the relative merits and drawbacks of a single rail with running boards vs. a traditional double rail?
There are a few theories here. A double rail actually distributes the weight on either side of the tube rather than the center. This is not really a big issue - just a function of how the mechanics work out. Adding running boards to a single rail config doesn't change this - in fact it reduces your usable space because if the frame is designed properly and your running boards don't straddle the outside rail, then more space is taken from inside the raft for said running boards.
With double rails, the rails will be equidistant from the center line of the tube. Thus your running boards will use space OUTSIDE of the space typically ending with the outside rail of a single rail frame.
To put things in pecking order I would put it like this:
1) Single rail
2) Single rail w/running boards
3) Double rail
4) Double rail w/running boards