1) All measures of suspension performance depend almost entirely on the paths of the following components relative to any reference frame defined by one of the bicycle frame members: Handlebars, seat, bottom bracket (BB), front and rear wheel axles, shock mounts, and rear brake.
This is the central idea of this work and is explored in the third chapter, “Path Analysis”. The following are the main conclusions that may be drawn from this statement.
The first thing that most people are concerned about with dual suspension bikes is efficiency under pedaling; generally assuming a seated rider position and a bike on smooth ground. But there are compromises that must be made in trying to attain this goal and most other goals associated with dual suspension performance. In reality, the right geometry for any one person will depend on that person's body type (mass distribution), riding style, sensitivity to various phenomena associated with dual suspension motion (such as bump feedback), desired ride quality (comfort, efficiency, etc.), and even the type of terrain in one's backyard.
No geometry is right for everyone and no frame can achieve for any one person every goal generally desired in dual suspension performance.
At suspension equilibrium (natural sag) or any other position in travel, any of the common suspension “types” (mono-pivots, various 4-bar configurations, etc.) can be as non-reactive to pedaling as any other during seated pedaling. However, no geometry can be completely “neutral” throughout a pedaling cycle, without friction. The deviation from neutral can be made small and a good suspension geometry with the right amount of friction can effectively limit oscillations, while remaining supple enough to absorb significant bumps. However, we note that no geometry is perfect in this respect as a warning against all theories purporting to provide a neutral geometry, in principle, without any qualifications.
A word on marketing:
No manufacturer of a bike or frame designed to run at sag (some bikes such as the Giant NRS are meant to run at no sag) is going to market its products with a valid, quantitative theory for constructing rear suspension geometry – telling you why their pivots or whatever are in the right place. The ideas and formulae would simply be too complicated to make a good marketing tool. This author has never seen a valid, quantitative, run-at-sag suspension theory put out by any company, though quite a number (some of which we examine later in chapter five, “Flawed Theories and Bogus Marketing”) market bikes under dubious claims and false theories – some asserting that you can have it all. If any manufacturer or sales person tells you that you can have it all, run away!
Our advice is to ignore all suspension theories and other claims put forth by frame manufacturers and industry magazines, and base your buying decisions exclusively on experimentation. That is, make your decisions by test riding the bikes, even if it is just a parking lot test (you can get a lot from a parking lot test). Ignore all marketing!