When it comes to performance off-road shocks for Tacoma’s and 4Runners it can be difficult to choose which shocks are right for your Toyota and your type of off-roading. In the past you had to choose which shock would give you the ride quality you wanted, and you’d put up with the quality (or vise versa). But with the advent of AccuTune Equations, you can now get any shock custom tuned for your Toyota, your weight, your terrain, and your preferences.  So now you can choose which brand, size, and configuration you want, and still get the ride quality you’re looking for. With that in mind there are now three things you want to consider when choosing shocks: ability to make proper damping force, heat capacity, and durability.

 

Why Does Damping Force Matter on Tacoma Shocks?

A Brief Background On Shocks:

Damping force is the amount of force produced by a shock at a given shaft velocity. Shocks make damping force when oil flows through ports in a piston and is restricted by round disks that act as springs. When shock diameter increases so does the amount of oil that has to flow through the piston, so naturally the damping forces increase. As a result there are ranges of damping where each size shock is most adequately sized.

Damping Force & Front IFS Coilovers:

The front coilovers on Tacoma’s and 4Runners are mounted about half way up the a-arm, which means the shocks only move half the speed of the wheel, and half the speed means half the force. Being mounted half way up the lower control arm also means that only half the damping force created goes to the wheel.  So on the front of Toyota 4×4’s the front shocks only deliver 25% as much damping force to the wheel as if the shock had been mounted there. This means that front Tacoma and 4Runner shocks need to make approximately four times more damping than the rear shocks. Four times more damping force means that 2.0 shocks really aren’t big enough.

For the purpose of completeness, there are tricks that can be done to valving to make shocks stiffer than traditional methods allow, and there are ways to design shocks which make them naturally stiffer. But aftermarket 2.0 shocks are ultimately not designed to make the forces required for the front of a Tacoma or 4Runner. Yes, we can make it work, but the when shocks are made to be stiffer than they naturally want to be it can lead to harshness are reduced life span. For this reason many undersized shocks are very soft and give you a bouncy, Cadillac like ride.

 

         

Summary:

Serious off-road driving requires serious damping forces, shocks that are too soft will bottom out frequently and will be bouncy off-road.  In the front 2.0 shocks are adequate for stock weight Toyotas doing on-road driving and slow speed off-roading such as hunting, fishing, and slower speed trail riding.  2.5 shocks are necessary for heavier Toyotas, and for high speed such as fire roads and desert running. In the rear 2.0 shocks provide enough damping force for stock weight Tacoma’s and 4Runner’s doing everything from on-road driving up to pre-running. With the addition of full overland gear such as skids, bumpers, and RTT it is necessary to step up to 2.5 shocks in the rear as well.

 

What is Heat Capacity and When Does it Matter?

Heat capacity is the ability for a shock to withstand rigorous off-road driving without fading, leaking, or substantially shortening their life span. When looking at heat capacity two things must be considered: amount of oil and speed heat dissipation.

The quantity of oil inside a shock relates to how much heat it can absorb, and heat dissipation is how quickly it can rid its self of heat. Larger diameter shocks hold more oil and have more surface area so it’s no secret they have better heat capacity. But Fox and Icon do make Aluminum Bodies 2.0’s with small 5/8″ diameter piston rods, which help them hold more oil, and dissipate heat more quickly.

When is Heat Capacity a Factor?

Heat capacity becomes a factor when running rough roads at speed for long periods of time. As an example washboard road causes extremely fast movement of the shocks which generate a lot of heat. On the other end of the size spectrum, large whoops also generate a lot of heat when run at speed because the shock is using its full stroke very rapidly. Any terrain which causes rapid wheel movement will be demanding on the shocks.

Summary:

Tacoma’s and 4Runners work well with 2.0 shocks for slow speed off-roading and about 5 minutes of hard run time on demanding terrain. The five minute run time is a rule of thumb and assumes the terrain is constantly rough and the speed is constantly high. With the increased oil capacity 2.5’s are good for about 15 minutes of hard run time before they start fading and life span gets shortened. Adding weight further reduces run time because it requires more damping which creates more heat. If you’re a light wheeler out exploring the backwoods with your 4Runner 2.0’s will handle the heat. If you’re blasting the dunes for an afternoon in your Tacoma then you should step up to 2.5’s for their ability to handle the heat.

 

What Influences Durability?

Shock durability is dictated by the size of the shock, quality of material, and reservoir configuration.

Size Matters For Hard Use:

As discussed previously, larger shocks naturally make more force. Part of this is because damping is directly related to the cross sectional area, so larger diameter shocks operate at lower pressures. Lower pressures are easier on seals and increase the shocks life cycle. In addition larger shocks are less likely to reach temperatures past their designed operating range.  Running a shock over temp doesn’t always make them fail right away, but it does harden the rubber seals and reduces the lubricity of oil, which leads to a shorter life span.

Quality of Materials:

We aren’t going to dive into the specifics of each brand here, but there are differences between the quality of materials used in each brand.

See our Fox vs King: 2.0 Coilover Shock Comparison article for more info.

Remote Reservoirs – Not Just About Cooling:

While it’s true that remote reservoirs do increase oil volume and thereby increase cooling and heat capacity, that’s not their primary purpose. The primary purpose of remote reservoirs is to reduce the shocks operating pressure. As the shaft goes into the shock body the volume is displaced and the nitrogen gas charge increases in pressure. Higher pressures drastically increase the friction and wear on seals, as well as reducing the ride quality. (note that nitrogen pressure is not a tuneable element of the shock, do not change from the manufacturers recommended pressure).

In an IFP shock there is a single cylinder containing the piston rod, oil, nitrogen, and Internal Floating Piston (IFP – which separates the oil & nitrogen). All of these items are in line which doesn’t leave much room for nitrogen, meaning the original 200 psi charge may exceed 600 psi when fully compressed. The 600 psi is actually not too bad, but once the shock starts heating up the oil expands and the pressures can sky rocket. The inline construction of IFP shocks is often done on an assembly machine which also seals the shocks, making them a sealed unit which can’t be rebuilt.

Remote reservoir shocks have a separate cylinder just for holding nitrogen, which has substantially more volume. As a result the pressure is very consistent, even when the shocks get hot. The remote reservoir design requires separate nitrogen charging, making them rebuildable.

There is a whole article coming about this topic, so stay tuned.

 

 

**Note in these pictures, the nitrogen space in the IFP is usually much smaller, and the nitrogen space in the Remote Reservoir is usually much larger (90% of the reservoir). Because these shocks were cut away the parts have been artificially moved.

             

 

Summary:

IFP shocks are a great budget solution for street use and slow speed off-roading but are not suitable for high speed use on Tacoma’s and 4Runner’s because the method of construction does not make them durable enough. Remote Reservoir shocks provide better ride quality and better long term durability than IFP shocks, and are well suited to hard use on demanding terrain.

 

What Do Compression Adjusters Do & Do I Need Them?

There are three types of compression adjusters on the market, low speed, high speed, and mid speed. Each one is designed to tune a specific performance characteristic of the vehicle.

Low Speed Compression Adjusters:

Low speed compression adjusters tune handling, g-out, and slow speed bottom out performance. In most cases low speed compression adjusters are a needle and seat which allows a small quantity of free flowing oil into the reservoir. Once oil reaches a high enough speed and pressure it flows through a separate set of spring washers into the reservoir, referred to as the high speed circuit.

 

High Speed Compression Adjusters:

High speed compression adjusters tune harshness and compliance on large hits such as potholes, whoops, and fast speed bumps. In most cases high speed compression adjusters take the high speed springs washers mentioned above and make it possible to tune the pressure at which oil will start to flow through the disks. By requiring higher pressure the high speed damping is increased.

Mid Speed Compression Adjusters:

Mid speed compression adjusters have some impact on low speed and high speed compression, depending where in the adjustment range they are. Fully open the mid speed adjusters tune high speed a little bit, and fully closed they tune low speed a lot (each adjustment is a large increment).  Mid speed compression adjusters are designed like a VERY LARGE low speed compression adjuster. They allow a large amount of free flowing oil when fully opened and allow none when fully closed. Oil not flowing through the adjuster passes through a set of spring washers.

 

Summary:

Compression adjusters allow you to easily and externally change the damping of your shocks. They are very useful if you’re adding weight for trips, picky about ride quality, or want to firm up that on road handling. Low speed compression adjusters are useful for on-road driving, and all types of off-road driving. High speed compression adjusters are most useful for high speed off-road driving. Mid speed adjusters are less effective than low speed or high speed adjusters and are useful for all types of on-road and off-road driving.

You can read more about the Fox & King Compression Adjusters here:

How Fox DSC Dual Speed Compression Adjusters Work

How King Compression Adjusters Work

Are Upper Control Arms Necessary For My Tacoma or 4Runner?

Stock upper control arms on Tacoma’s and 4Runner’s are the first item to bind when the suspension extends. By replacing them with a tubular or billet arm the suspension is able to gain one inch of droop. One inch of travel may not seem like a lot, but many lifted Tacoma’s only have 2-3″ of droop, so that extra inch makes a big difference. When you don’t have enough droop the shocks will clunk hard against their extension stops and will feel very harsh on potholes, washboard, and any bump that requires more than two inches of movement. When the wheel has no down travel it can’t follow the terrain so it jerks the chassis down into the hole, then bangs back hard on compression when it hits the face of the obstacle. With sufficient down travel the tire smoothly follows the contour of the road.

Summary:

If you are lifting your Tacoma or 4Runner more than 1.5″ it is necessary to install an upper control arm to get the full benefits of the upgraded shocks.