An in depth look at the operation of one of the most popular shock absorbers in the high performance market

A shock absorber's job is to simply control the movement of the suspension. Nearly every shock absorber does exactly that... control the suspension, rather than 'absorb' the shock. The springs, bushings, tires, and even the seat of your pants "absorbs" the shock. Shock absorbers are not intended to intercept the initial upward movement of the suspension when meeting a high speed bumpů this is the primary responsibility of the built in strength of the suspension's spring rate. To use a shock absorber to "cover up" for a weak or inadequate suspension will get you the roughest ride in town with ill-handling characteristics.

Some of the older designed and heavily charged gas shocks (with up to a 200psi pre-charge) may actually slightly lift an extremely light vehicle, say 1/4" or so when used in multiple shock per wheel applications, however, the ride would be near unbearable. These types of shocks are charged with nitrogen gas to pressurize the expanding oil when the shock heats up, in order to eliminate foaming and allow expansion of the heated oil. Rancho 9000's are of the 'cellular gas' design, which in essence means there is a foam-like solid material made up of tiny nitrogen bubbles encasing the inside tube of the body,  which eliminates any air gaps from forming while allowing expansion when the fluid heats up. This is a much more reliable and better performing design with less chance of leakage.


Many off road racers run the shocks body side up (with the exposed shaft side down), and install the boot with the bottom cut off, to act sort of like a 'dangling skirt'. This allows any and all debris to fall off the shaft during usage, and yet still protects the exposed surfaces from flying rocks, etc. However, this looks kind of  'trashy' on a street truck, giving an unfinished appearance. Therefore, removing the boot completely would be the better bet to keep the shaft clean and allow easy periodical visual inspection. The so called 'dust boots' are just that, for keeping only dust out, so if that's the only terrain encountered, then that's what they'd be used for. So why do shocks even come with these 'evil' boots? A lot of shock buyers like them for their looks. simple.

The Rancho 9000, although has 800% of manually adjustable valving, is also speed sensitive 14 stage internally valved as well. In other words, the faster the piston travels, the firmer the dampening becomes... to a point. The external adjustment is primarily for setting the initial load as desired. The absolute smoothest ride would have to come from the RS-9000 Rancho shocks, since they valve only under high speed movements on the compression stroke, therefore enabling the best ride without interference (with the suspension as the only resistance.) I've found none better... so far.

The Rancho Reflex design has similar internal valving, however, this valving is designed to become 'softer' as the piston speeds up... therefore 'dampening' the ride on stiff bumps. Bottom line, Rancho admits the Reflex (and accordingly, the Edelbrock IAS) is designed more for smooth riding vehicles with minimum travel in low speed mild terrain situations. In other words, street driven or slowly driven trail riding off road. For heavier vehicles, higher spring rates, long travel suspensions and high speed off roading and/or jumping, the 9000 would be much better. As a side note, a Rancho engineer stated that the Reflex was 'somewhat' based on the Monroe Sensa-Trac (same company), yet the original sensa trac design did not stand up to their testing, so a much improved version was created... The Reflex.

Performance Unlimited customers buying RS 9000 shocks have the secure comfort of knowing that the shock they buy from me will be warranted forever. That's right, FOREVER. As long as they're not physically damage or modified (dented tube, bent shaft, etc.) due to abuse or accidents, you'll get a free one if they ever fail. This isn't a sales pitch, I've been doing this type of warranty service for the past 10 years. We can, since we sell more 9000's than anything else, after an annual sales of 1500 shocks, I've only seen 3 or 4 units needed to be warranted. That's less than 1/2 percent failure rate. You *don't* want to know the failure rate for the one's you may have on your truck now.

How to Measure for Rancho 9000 Shocks

Even though most shock catalog's recommend a general part number for a particular application, ride heights can vary greatly from vehicle to vehicle. The alternative 'hit and miss' option of relying on the catalog alone and possibly resulting in the headaches and wasted time of returning shocks that may not end up fitting, does not really outweigh the few short minutes it takes to measure the ride height of your shocks. Besides this, since you will basically have "lifetime" shocks, you should really get the absolute best fitting shock you can, again, as long as it only takes a few minutes. Wouldn't you agree? Since vehicle heights can vary greatly from one to another, if a respectable 6 inch travel shock is off by only one inch, that will change a 3" up, 3" down travel to a 4" up, 2" down travel... which could cause premature damage due to either the shock topping out, or worse, bottoming out. This of course, voids the warranty.