Question: For bikes like [these](http://www.herocycles.com/images/octane-recra.jpg), why aren't the rear shocks (the shocks are directly above the pedal) vertical like those of a motorcycle? I don't see how the bike can take shocks when the shock absorber is at such a low angle. 

A friend said the mud-guard is so high because there's no other way to attach it to the cycle at a lower height. Is that really the reason why the mud-guard is so high?

Answer: 
From my understanding, one of the major features for bicycle suspension is vertical travel. This is to increase pedal efficiency and rear wheel feel. This is why you see engineers jump through hoops when designing rear suspension for bicycles. For example, take a look at the [Pivot Mach 429](http://www.29eronline.com/wp-content/uploads/2009/01/side-view-pivot-convert.jpg). If I count correctly, this bike has 5 points of rotation to accomplish beter pedal efficiency as well as offering more rear-wheel travel. Some motorcycles do have non-vertical mounted suspension as well; the first to come to mind is the [Kawasaki Ninja 650](http://www.motosavvy.com/_ImageAreas/Kawasaki650R-3.jpg). 

As for the "mud-guard", that is often referred to as a [filth prophylactic](http://bikesnobnyc.blogspot.com/search?q=filth%20prophylactic). This isn't intended to do much more than keep mud off your shirt and backside. [Full fenders](http://cdn1.media.cyclingnews.futurecdn.net/2011/02/26/2/cielo_sportif_full_view_600.jpg) can be quite difficult to mount to a full-suspension bike (everything keeps moving, man!) so filth prophylactics are common "good enough" equipment. They also tend to have very little in frame requirements (full fenders require braze-ons for mounting them), so they fit on most any bike.
The fender or "mud guard" is so high because if it was much lower the tire would be banging into it whenever the shock compressed.