What is the significance of rear travel of a frame? Every suspension frame has the the following two parameters: shock travel and rear axle travel at maximum shock compression. I have a lot of questions, regarding those two:


What are they properly called?
They seem related, however for the same shock travel the rear travel can differ. I would intuitively guess that long rear travel for short shock travel would be best. However, this is not the case (I saw an expensive frame with less rear travel than a cheap frame). So what shock and rear travel would I want for different types of mountain riding?
What are they properly called?


Rear wheel travel (e.g 180mm) and shock travel (e.g 3 inches [76.2mm]).


  They seem related


Theoretically they are not. One could design a pivot system which would give 180mm of rear wheel travel with a 18mm shock travel. This would not work correctly though.

The ratio between the wheel travel and the shock travel is called the suspension leverage ratio. A 180 to 76.2 setup gives us a leverage ratio of ~2.36 to 1. Some companies (e.g http://foesracing.com/) claim that a lower leverage ratio (e.g 2:1) has significant advantages for downhill racing.


  So what shock and rear travel would I want for different types of mountain riding?


You'll only choose the rear wheen travel based on what you want to do. For example if you want to do downhill racing then 203mm is the norm. Whichever brand and frame you choose will come with a rear shock installed which has very specific size specifications, e.g 9.5x3 (that is eye to eye and shock travel in inches) and even if you wanted to change the rear shock you'd have to go with those specs.