If you're shopping for long travel suspension, you'll see two kinds of shocks everywhere: coilovers and bypass shocks. Most serious prerunners run both. Here's what each one does and why.
What a coilover does
A coilover is a shock absorber with a coil spring wrapped around it. It does two jobs at once:
- Holds the truck up. The spring carries the vehicle's weight and sets ride height. Most coilovers have a threaded collar, called a preload ring, to adjust height.
- Controls movement. The shock inside slows the spring down so the truck doesn't bounce.
On most long travel kits, the front coilover is the main suspension part. It's required, and it's built to the kit's spec. Some coilovers, like the King and FOX Raptor coilovers, have an internal bypass: damping changes depending on where the shock is in its travel.
What a bypass shock does
A bypass shock has no spring, so it doesn't hold the truck up. Its only job is damping, and it's much more tunable than a regular shock.
The tubes on the outside of the shock body let fluid bypass the piston in certain parts of the stroke. Each tube has an adjuster. That means the shock can be:
- Soft in the middle of its travel, for a smooth ride over small bumps
- Firm near the end of its travel, to stop big hits from bottoming out
You'll see them called 2-tube, 3-tube (triple) or 4-tube bypasses. More tubes means more zones you can tune. A shock tech can adjust them without taking them off the truck.
One thing to know: bypass shocks can be noisier than regular shocks, because the needle valves click as fluid flows through them.
Why prerunners run both
On a typical prerunner:
- Front: coilovers hold the truck up, and front bypass shocks (mounted in shock hoops) add damping control for big hits.
- Rear: leaf springs or coils hold the truck up, and rear bypass shocks (mounted in a bed cage) do the damping.
If you're just starting out, coilovers alone are a big upgrade. Add bypass shocks when you're driving fast enough that the truck bottoms out or feels unsettled in rough sections.
Reservoirs and cooling
Shocks get hot on long, rough runs, and hot shock oil gets thin and fades. That's why off-road shocks use reservoirs (extra oil and gas outside the shock body):
- Piggyback reservoirs attach directly to the shock.
- Remote reservoirs connect with a hose and can be mounted elsewhere.
- Finned reservoirs shed heat faster.
FOX or King?
Both are race-proven and both make excellent off-road shocks. Dirt King offers spec-built versions of each for its long travel kits. Most people pick based on experience, what's already on their truck, or the adjusters they prefer.
Shop all shocks and coilovers, FOX or King. Not sure what your build needs? Email sales@bajaracingparts.com.