5 Fox Shocks for Jeep JKs

Shocks are also known as "shock absorbers". This isn't a really accurate name though, since they really work together with the coil springs on your Jeep JK to absorb shocks from the road or trail.

First, let's get one thing out of the way quickly: 

Shocks don't lift your Jeep JK. Lift comes mainly from longer coil springs or coil spring spacers. Most lifts require longer shocks, and larger lifts may also require new control arms, longer brake line, new driveshafts, and other mods.

Shocks are really a damper, working to calm your Jeep's springs after hitting bumps and ruts.

Coil springs hold up the weight of your Jeep - they extend into dips and compress to absorb bumps. While coil springs are built to compress in response to a given amount of weight, you can't tune them to compress and rebound in a controlled way.

Once you compress a coil spring, it wants to decompress as soon and as quickly as possible. In the compressed state it holds potential energy.

Enough potential energy can cause the spring to rebound into an extended state. Since the extended state pushes your Jeep up, it'll slam down on the coils again and store potential energy again. The spring can again rebound into an extended state. This bounciness can continue on for far more than will be enjoyable!

Now:

This process happens very quickly, but what it results in is a very bouncy ride, especially on a trail. Since most trails aren't smooth, it'll just feel like you're pogo-sticking down the trail.

Clearly, this isn't what we want. For one thing, it's very uncomfortable and makes you fatigued as you try to hold yourself in place. If you've ever been lucky enough to have a rig with clapped-out suspension, you know exactly what this is like.

More importantly, it's impossible to maintain good steering, braking, and acceleration control if your tires aren't sticking firmly to the ground.

So what do we do?

We want to compress and decompress the spring in a controlled way, and that's what a shock does. The damping provided by the shock absorbs a portion of the energy that the spring wants to use to throw your rig into the sky and turns it into heat.

Inside the shock, there are two components that make the shock work the way it does:

• Hydraulic Fluid (oil)
• Little holes

When the shock extends and compresses, the oil simply moves between different reservoirs in the shock through little holes. How your shock responds to bumps and holes depends on the size of the holes and their orientation.

Imagine you have a syringe (we like to use the type with a plastic tip for getting lubricants into tight places). When you push the plunger of a syringe, you squirt liquid out of the bottom orifice. If the orifice is small, the plunger is harder to compress. If the orifice is large, the plunger is easier to compress.

Now, if we connect the orifices of two syringes together so that fluid flows back and forth between them, you have something that functions just like a shock - fluid moving back and forth between two "reservoirs" through a small opening.

Some Fox shocks can be adjusted to make oil flow faster or slower, and top of the line Fox shocks allow you to make these adjustments for slow speeds and fast speeds.

With a lot of movement at high speeds, shocks can start to "fade", meaning that they become less effective at dampening. This is because the shock is absorbing all that suspension energy and converting it to heat. It causes the hydraulic fluid to become hot and aerated.

How do you solve this?

By adding a remote reservoir:

A remote reservoir sits outside the shock body and increases the amount of hydraulic fluid in a shock.

You can think about it just like the oil in a car or motorcycle - a vehicle with more oil capacity can often have less frequent oil changes for a given engine size, since, on the whole, it takes more time to break down than a lesser amount. (Although, in this case, the oil isn't fading because of breaking down, it's just getting too hot.)

You can get remote reservoir shocks with the reservoir attached to the shock body, or with the reservoir only attached with a piece of flexible tubing - you take care of mounting the reservoir.

Do you need a remote reservoir?

If you're in your Jeep a lot on and off road, you might appreciate it more. Generally, we'd recommend remote reservoirs more for those that want to run at high speeds. However, a lot of wheelers have been really happy with having the better valving and performance that comes with a reservoir shock.

A better question to ask is probably this:

How important is valving to me?

With Fox shocks, reservoirs mean that you get at least low speed compression damping and all Fox reservoir shocks are valved specifically for your Jeep model. While a reservoir can improve your performance by not allowing your damping to suffer in hard use, the valving determines how nice your ride is.

In any case, Fox has an assortment of shocks that'll work just fine.

A typical shock has these base-level specs:

• 2" body
• Steel body
• 5/8" shaft
• No remote reservoir

If you walked into a 4x4 shop and asked for a set of shocks for your Jeep JK, this is the type of shock you'd expect to get.

Among the different Fox shock offerings, you have more options:

• 2" or 2.5" body
• Steel or aluminum body
  
• 5/8" or 7/8" shaft
  
• Remote reservoir attached or detached
  
• Compression damping adjustment
• Dual speed compression adjustment
• Rebuildable
  

As with most things, the more you pay, the better the performance. It is really the case with shocks though, because the prices really vary around the kind of valving and adjustability you get.

The most important thing to know is that the valving improves with each level of shock in the Fox JK line. The Adventure Series has generic valving, the Performance Series has application specific valving, and the Factory Series has application specific valving with high and low speed adjustment.

Durability increases as well, with the more expensive shocks being larger with more durable materials.

If you're truly on a budget, we'd look at the Performance IFP as it'll improve your ride significant, can be rebuilt, and is valved for your JK.

So let's take a look at a few shock options:

A larger diameter body will hold more oil and be stronger than a smaller diameter body. By itself, this will reduce fade and be a little more robust.

Aluminum is lighter than steel and will dissipate heat more quickly than steel (although this is probably negligible). If you're really counting pounds with aluminum wheels, a fiberglass hood, a small Li-PO battery, and that sort of thing, aluminum shock bodies will save a tiny amount of weight. The aluminum alloys that Fox uses won't be any weaker than steel.

A larger shaft is obviously stronger than a smaller shaft. It'll also take up a little more space in the body, reducing fluid volume.

Fox offers JK shocks without a remote reservoir and with the two types of reservoir we talked about above.

This allows you to make your ride firmer (for general road use or towing) or softer (off road). This is an add-on for the 2.0 reservoir shocks and is somewhat similar to Rancho's 9000 series adjustable shocks. Basically, you get a knob that you can turn to firmer or softer. However, these shocks are more performant than the Ranchos due to the remote reservoir and application-specific valving.

This is super expensive, but also super cool. These adjusters only fit 7/8" shaft shocks. You get two adjustment knobs. The high speed knob has 12 levels of damping for bombing over sand dunes and the low speed knob has 10 levels of adjustment for running rocks.

This is overkill for the vast majority of Jeep JKs like daily drivers - if you don't know whether you need it, you don't!

All Fox shocks in the Jeep JK line are rebuildable except for the Adventure Series. You can send your shocks to Fox, a local suspension shop, or do the rebuild yourself. Rebuilding shocks isn't hard, but you need the right tools.

You'll probably require some outside help. For instance, you probably don't have a rig to add nitrogen to these shocks, but a competent local auto or mototcycle shop will be able to do it for you.

Fox publishes fairly low rebuild intervals, but it's probably safe to assume that you can push these out a little bit if you aren't absolutely thrashing your Jeep on a regular basis.

There are five basic models of Fox shocks for Jeep JKs. These shocks will fit any JK from 2007 to 2018. Make sure that you select shocks for the amount of lift you have. Fox shocks are available from stock heights all the way up to 8".

Note that not all models are available for all lift heights.

This shock is the most basic shock that Fox makes for Jeep JKs. Most people report that they're pleasantly surprised with the upgrade in ride and handling characteristics. It's available in lifts from 0-6".

Check prices here:

• For Jeep JKs with 1.5-3.5" lift
  
• For Jeep JKs with 4-6" lift front / For Jeep JKs with 4-6" lift rear

The body is 2" steel alloy, so it slots right in with most common shocks.

As the "low end" of the Fox JK line, it has the basic characteristics you'd expect from most shocks: 5/8" shaft, 2" steel body, and no reservoir, but it's a well-engineered shock that'll improve your ride and control from the generic shocks you get with a lift kit.

IFP stands for Internal Floating Piston, which is designed to reduce aeration. Oil is also separate from nitrogen - in most generic shocks they mix together, which decreases performance when the oil becomes aerated.

The valving on these shocks is somewhat generic, meaning that they aren't necessarily tuned as well as something like the Performance Series shock.

Also, the powdercoat is nice, since it should last quite a bit longer than paint.

You can buy this shock without fear if you want a budget option to upgrade how your JK rides. However, you might want to consider the Performance IFP. For just a little more money, you'll get a better shock that is rebuildable. Once the Adventures wear out, you have to throw them away.

This shock is similar to the Adventure Series, but comes with a few upgrades. Like the Adventure, they fit lifts from 0-6". But unlike the Adventure the shock body is clear-anodized 6061-T6 aluminum, so it'll never rust and it should run cooler than a steel Adventure shock. 

Check prices here:

• For Jeep JKs with 1.5-3.5" lift
  
• For Jeep JKs with 4-6" lift 

Another big difference is that the Performance Series shocks have application-specific valving. Basically, these shocks are specifically tuned to JKs with a specific height.

If you're wondering how this works, think about it like this:

Remember how we said that shocks have little holes that oil passes through? Adventure shocks are made with the same holes in the same spots for different vehicles, more or less.

But a Performance Jeep JK shock has holes sized and oriented to make the perfect valving for a JK. A Jeep XJ or a Toyota 4Runner will have different holes sized and oriented to make their own respective perfect valving.

In addition to that, the seals are upgraded over the Adventure Series. This is a great shock if you want a little more performance on a budget. Between this and the Adventure, the Performance Series is worth the small cost difference.

So if you take all the good characteristics of the above Performance shock and add a reservoir, you get the Performance Reservoir shock. These shocks fit lifts from 1.5-6".

Check prices here:

• For Jeep JKs with 1.5-3.5" lift
  
• For Jeep JKs with 4-6" lift 

It has a clear-anodized 6061-T6 aluminum 2" aluminum body and application specific valving. You can also adjust the compression damping on this shock with a small adjustment dial.

The reservoir isn't hard mounted on the body, meaning that you can attach it to a shock hoop if you need the space. Of course, with the aluminum body and remote reservoir you'll get the most effective cooling of all the Fox 2.0 shocks.

Between the fade-reducing cooling and the compression adjuster, this is the most performant of the 2.0 shocks.

One thing is for sure: Ain't no "budget" about this shock! This is a heavy duty shock for hardcore use. The body and reservoir are a larger 2.5" diameter alloy steel. The shaft is a burly 7/8". For JKs, they'll fit lifts of 0-6".

The remote reservoir keeps the shock cool for heavy, hot use. Damping is improved over the 2.0 series and you also get dual speed damping adjustment knobs for extra control.

If you haven't figured it out, this is a very high performance, heavy duty shock. And it'll bolt right in to a Jeep JK. You probably don't need it unless you're bombing over whoops on a regular basis, or unless you just love dumping money in to your Jeep!

This shock is the next level up from the Factory Series shocks. There are two main differences:

• The 7/8" shock shaft gets an upgrade to chrome-plated 17-4 H900 stainless steel 
• Internal Bypass tech: In other words, this shock has internal passages that allows fluid to bypass the piston through additional holes. It's like adding another level of tune to your shocks.

Like the regular Factory Series it also has the the dual speed damping adjustment. This is a shock that can be and needs to be periodically rebuilt. It you need to hit potholes and ruts at 75 mph, this is the shock for your JK.

This shock has the most advanced valving of the shocks in Fox's Jeep JK line.

For the more expensive shocks in Fox's line it's extremely important to get a shock that matches the specs of your JK.