These are the components that...
These are the components that make up a JounceShock. On the left is one of two styles of mounts available that attach, via a thread-on design, the JounceShock body to the vehicle's frame. This mount is welded to the frame. In the middle is the JounceShock itself. They are available in two sizes: 1 1/2 inches and 3 inches of travel (shown here). The 1 1/2 is 6 inches long overall, while the 3-incher is 9 inches long overall. Both bodies are the same diameter and use the same frame mounts and feet. Below is the thread-on nylon "foot" that comes in contact with the weld-on "target" below it when the vehicle's suspension travels upwards. The feet and targets are available in corresponding convex and concave shapes to fit different applications.
When it comes to suspension design, proper spring rates and great damping are essential to maintaining control at faster speeds. Faster speed over rough terrain creates more suspension movement, and eventually you run out of it. It is just before this bottom-out point that a secondary suspension system is crucial to vehicle durability/survivability and a fluid ride that doesn't compress your spine into that of a midget.
A secondary suspension, usually a rubber bumpstop, is utilized in almost all OE suspension systems. While OK for street use, when subjecting a vehicle to rough off-highway abuse, the limitations of a chunk of rubber become readily apparent. This is where Light Racing's new JounceShocks come into play.
The JounceShock is a nitrogen- and oil-charged cylinder and shaft that, when properly installed, only comes into play during the last one half to one third of your vehicle's suspension travel. The body of the JounceShock is attached to the vehicle's frame, while a "target" or contact pad is attached to the moving axlehousing (live axle application), or lower control arm (IFS or IRS application). When the suspension nears its maximum upward travel, the target comes in contact with the moveable shaft of the JounceShock. The suspension's upward force pushes the shaft into the J'Shock body, which is filled with nitrogen and a bit of oil. Via valving, the shaft compresses the nitrogen, causing its pressure to increase dramatically since the cylinder is small and the travel of the shaft is 1.5 or 3.0 inches, depending on application. The increased pressure absorbs the force of the upward traveling suspension as a smooth exponential increase in force instead of a force spike which would occur if the suspension went metal to metal. (Read: painful spine compression.)
 Jumps like this are not a...  Jumps like this are not a problem for the old Bee these days. When the rig comes down and the coilovers compress 11 of their 14 inches of travel, the JounceShocks come into play, and the final 3 inches are soaked up in a steep, progressive curve of energy absorption that translates into a smooth landing with no jarring jolt. |  1. I utilized the 15-degree...  1. I utilized the 15-degree upper Flex Mount to attach the JounceShocks to the Bee's frame. Light Racing offers a ridged fixed mount for this position as well. You can see how the J'Shock body threads onto this mount after it is welded into position on your frame. |  2. Here, a Flex Mount is tacked...  2. Here, a Flex Mount is tacked to the bracket I fabricated off of my frame in the proper position for a 1:1 contact ratio with my front axle when the front suspension bottoms out. Besides the universal application used here, Light Racing has kits available for some specific trucks. These kits incorporate this upper mount into special, weld-on mounts designed to fit in the optimum frame locations for these given vehicles. |
Once the upward travel energy is absorbed by the valving in the JounceShock, the suspension will rebound in the opposite direction (the speed of which is controlled by the regular shock absorber). Meanwhile, the valving inside the JounceShock doesn't allow it to rebound as fast as the suspension, so it doesn't contribute to pushing the suspension back out (like a rubber bushing will). This energy dissipation is one of the key reasons JounceShocks are so effective in controlling a vehicle when it's driven at high speeds over rough terrain.
Since a JounceShock is not engaged until the end of a vehicle's suspension travel, on-road ride quality and ride height are unaffected. However, handling with a heavy payload can be improved if the suspension squats enough to engage the JounceShocks during sharp cornering or big bumps. Once off-pavement and driven at speed, your rig will feel like it never bottoms out and it will bounce around less. Care must be taken, as this added suspension capacity can mislead one into thinking the overall vehicle is now stronger and can take blows like a Trophy Truck. An example of this came when the military was testing otherwise-stock GM trucks equipped with J'Shocks for use as Border Patrol rigs. The ride was so good, they unknowingly beat the trucks so hard that their frames spread and the engines fell out of the bottom of them!
 3. This is an exploded view...  3. This is an exploded view of the Flex Mount. It incorporates a rubber O-ring that allows for flex, yet also keeps things centered. This mount's purpose is to provide up to 7.5 degrees of misalignment in any direction when the J'Shock's shaft contacts the target. This is useful in reducing side loads to the unit in IFS applications where the suspension travels in an arc. It is also beneficial on a rockbuggy that misaligns its axle to its frame during huge flex. When using the Flex Mount, a concave or cupped foot and convex, or domed, target are recommended. This is the setup I went with, and it seems to work well in deflecting the JounceShocks during big flex. A ridged upper mount and domed foot and flat target are also available; these might work better in some applications. |  4. The bottom of the JounceShock,...  4. The bottom of the JounceShock, where the nylon cupped or domed foot threads onto the shaft. Note the yellow cap in the center. Under this cap is a Schrader valve for changing the nitrogen pressure or the oil. My J'Shocks came with 80 psi of nitro, which proved to be too stiff for the 3,500-pound Bee. Reducing the pressure to 40 psi made a huge difference. By the time you read this, Light Racing will have probably reduced the initial 80psi pressure to 40 in all its universal applications. Also note the small hole at about 4 o'clock on the shaft. This is one of two holes around the base of the shaft that contain adjustment screws for fine-tuning the compression and rebound valving. |  5. This shot gives you an...  5. This shot gives you an idea of the overall size of a 6-inch-travel JounceShock. The silver-domed target is welded to the axlehousing in the exact location where the mounted J'Shock shaft makes contact when the suspension is 3 inches from being fully compressed. You can also see the valving adjustment screw a little better here. |
So all this is great for going fast, but why put them on a rockcrawler? Well, if crawling rocks is all you do with your rig then yeah, they would be unnecessary. However, I like my rig multifunctional. It's more of a dual-sport rig these days that can go fast or slow. The beauty of JounceShocks is that, for slow rockcrawling, they don't have any negative effect. I haven't noticed any change or limitation in articulation during extreme flex, and in fact, it feels more stable when completely twisted up or when climbing walls where the weight transfer is heavily rearward.
JounceShocks are available in a universal application. Light Racing also has developed specific kits to attach them to Toyota Tacomas, 4Runners, and the new FJs, as well as late-model F-150s and GM pickups. More applications are under development, including TJs and the new JKs. Pictures better explain the several clever ways J'Shocks are mounted, so check out the photos. And if you're ready to go faster in your rig, don't forget that all-important secondary suspension that takes the shock out of your jounce.
 6. The complete JounceShock...  6. The complete JounceShock assembly as mounted at the right rear of the Killer Bee. Note that the mount you fabricate must be strong enough to withstand the blows of a harsh bottoming-out. Gussets and triangulation help here. |  7. For slow rockcrawling,...  7. For slow rockcrawling, the JounceShocks do not hamper articulation. They do, however, make the rig feel a little more stable when teetering on opposing axle ends. |  8. When leaping off of whoops,...  8. When leaping off of whoops, its reassuring to know when you come crashing down you've got JounceShocks to cushion the blow. Just remember, even though your ride may feel more indestructible, it's only as strong as its weakest part. After about a dozen jumps to get shots for this article, a 10-year-old control arm broke and ended our photo session. Back to the drawing board ... |