This particular Bilstein 9100 Series coilover is destined for Project TrailRunner, a long-travel 4x4 Ford Ranger built for high-speed desert use. 9100 coilovers are more robust than their younger-brother 7100 shocks. The 2.65-inch-diameter body holds a generous volume of oil for greater fade resistance. Smaller, lighter trail rigs are usually fine with smaller-diameter shocks such as Bilstein's 9100 Series 2-inch-diameter coilovers. What about air shocks? Experience has shown that air shocks should be reserved for super-light trail rigs and pint-size competition buggies. 4 WHEEL DRIVE & SPORT UTILITY Editor-in-Chief Phil Howell initially used a set of air shocks on a project TJ. The TJ's weight required a lot of air pressure to support the vehicle. The high air pressures translated into shocks that topped out (hit their full extension) merely pulling away from a stoplight - obnoxious. The air shocks were shelved in favor of coilovers, with much better results.
Here's a Bilstein monotube shock that features application-specific valving. It is designed to not only bolt into place using the stock mounts, it has been tuned for optimal performance for its intended application. This tuning makes a real difference: You may be able to physically bolt the same shock onto the rear of a compact Toyota pickup and a diesel-powered Ford Super Duty, but their shock-tuning requirements are galaxies apart. | 
Bilstein's 7100 Series remote-reservoir shocks increase oil capacity by moving the nitrogen chamber from the main shock body into the reservoir on the end of the Aeroquip hose. 7100's are available in a variety of stroke lengths, including short-body versions. Several application-specific models are available, as are models with nonspecific valving. The nonspecific models are intended to be custom-valved once they're mounted to the vehicle and some in-the-dirt testing has been done. | 
King Shock Technology offers a high-quality product and outstanding customer service. While most of King's lineup is destined for custom-fabbed shock mounts, this piggyback-reservoir smooth-body shock is valved and configured to bolt right into place on the rear of Ford's latest-generation F-150. |
External-bypass shocks feature position-sensitive control and easy tuning. They're close to ubiquitous in desert racing but are seldom seen on trail rigs. Although a set of bypass shocks would indeed add performance and control to a trail rig, they're not for everyone. The reason? It's not cost. It's noise. The check valves inside the bypass tubes emit a clattering sound as they open and close. |  | 
Here are two ways not to build shock mounts. The photo to the left shows strong construction but incorrect shock-tab placement. The tire rubs on the shock quite badly, evidenced by the missing paint. Missing paint isn't too big a deal, but the missing adjustment knob is. During a particularly hard hit, the tire came up and took out the knob. The upper photo shows a cracked frame caused by inadequate coilover mounts that concentrated too much stress in too small an area. A better strategy would have been to weld a mounting plate to the frame and then weld the shock hoop to the mounting plate. |