We bet that risk factor was low on the minds of Ford's top executives when they decided to retire the Super Duty's tried-and-true front leaf packs in favor of coil springs for 2005. Coils are a proven concept, as everyone from designers and engineers to end users would agree. The switch prompted praise from all, including us. We predicted the revision would vastly improve ride quality on what some say is still the undisputed leader when it comes to hauling.
However, much of the benefit associated with coil springs was sacrificed on the Super Duty due to a combination of inadequate factory dampers with overly stiff coil springs. Unfortunately, the silky-smooth ride quality that much of the industry expected from the new configuration wasn't present in stock form. But we had to give Ford credit for making the change, successfully opening up a plethora of aftermarket opportunities that could improve both ride quality and performance. The move was good for all of us in Truck Land.
The proof of this became crystal-clear when Pro Comp introduced its new Double XX kit which features four-count 'em-custom-tuned 2.75-inch front coilover shocks, each with a remote reservoir and high-quality progressive-wound coil spring. Why four? The answer lies in dependability. The last thing you want to deal with in the middle of nowhere is a broken coilover shock, so Pro Comp, like many professional desert racers, spread the burden between two coilover shocks at each front corner. Doing so effectively improved the odds of dependability and strength.
Just like a roulette table in Vegas, we couldn't pass up a spin. So we tested the new 8-inch Double XX arrangement (also available in a 6-inch version). Follow along as we show you all the trick components, a few must-have complements to the kit, and our results from a full year's worth (50,000 miles) of testing by one of the most destructive volunteer testdrivers we know.
 1. The first thing to understand...  1. The first thing to understand about this kit is that the factory coil-spring bracketry goes away. To do this, Pro Comp's guys used an air chisel to cut the heads off the five factory rivets securing the stamped-metal spring bucket/shock mount to each framerail. Some dealers might argue against chassis-related warranty claims after seeing this; it all depends on the dealership. |  2. Pro Comp teamed up with...  2. Pro Comp teamed up with Tenneco to produce vibration-damping rubber bushings for its heavy-duty tubular radius arms. Tenneco is one of the world's leaders in bushing technology, not to mention an OE supplier to Ford, so we're confident that these little units are either as good as, or better than, the factory bushings when it comes to vibration isolation and/or service life. |  3. Here is the new dropped...  3. Here is the new dropped mounting bracket for the front track bar supplied with the Double XX kit. It doesn't win any points with us for aesthetics, but it should be plenty capable of doing its job locating the front axle, side-to-side. A durable gray powdercoat protects it from corrosion. |
 4. The kit also includes a...  4. The kit also includes a forged dropped pitman arm to correct steering geometry. |  5. This is where we started...  5. This is where we started scrutinizing the kit. This is the lower shock mount as it looks prior to mounting either of the two 2.75-inch coilover shocks. Notice how the outside of each shock mount is not supported by any brackets or anything? Now, notice how one large bolt secures this piece to the top of the front axle's inner "C". Conventional wisdom advises mounting any weight-bearing coilover shock in a double-shear manner (in a way that captures both sides of the shock eye/bolt). At this point we stopped the installation and asked for clarification from Pro Comp's engineers. |  6. Here is what Pro Comp's...  6. Here is what Pro Comp's design engineer shared with us to convince us that, in this specific case, single shear would do just fine. From front to back: final zinc-coated production part; raw, uncoated part after machining; and a solid billet of hot-rolled 4140 2-inch steel round stock. As 4140 is a very expensive metal, this is about as tough as steel gets without being ultra-pricey. We agreed that the use of this super-high-grade material would suffice to mount a pair of coilover shocks in the intended manner for this particular application. However, we kept a close eye on this during our evaluation. |
 7. Plenty of strength here:...  7. Plenty of strength here: This is the top of the Pro Comp shock tower, where the top of each coilover will mount. We thought this part looked very nice and were not at all concerned about strength. |  8. Here you can see the complete...  8. Here you can see the complete front Double XX package as it looked once mounted to our donor truck. Note the 1 1/2-inch DOM support hoop designed to triangulate the shock brackets while providing a simple and clean method of attaching each shock's remote reservoir. Pro Comp builds each coilover shock in-house using custom-tuned valving and high-quality components. |  9. Out back, the Double XX...  9. Out back, the Double XX kit uses a combination of arched leaf packs and lift blocks to attain 5.5 inches of lift, effectively setting the rear of the truck level with the front. A pair of Pro Comp MX6R remote-reservoir shocks helps to slow axle movement while allowing users six levels of damping effectiveness. |