Bilstein 5100 Ride Height Adjustable Shock Installation

Sep. 19, 2016 By Josh Burns
The Bilstein 5100 shocks will not only offer improved off-road performance over most stock suspension setups, but they also offer an inexpensive way to achieve some additional lift on the front end as an alternative to coil spacers.

When the performance of the shocks on your truck or SUV starts to fade and you’re looking to replace them there are a number of options to consider. The first thought might be heading to the dealer for a direct replacement part, but that path is likely not going to be a cheap one. There’s also the option to make the jump to an upgraded coilover or remote-reservoir shock, but although a high-end off-road shock will improve performance it can also be a serious investment.

There’s another alternative that falls somewhere between the two options above. The aftermarket offers multiple direct-replacement options that not only will get your rig’s suspension back up to speed but also might actually help improve the off-road performance without breaking the bank. Bilstein’s 5100 Ride Height Adjustable shocks certainly fit that description. The 5100s – known for years by off-roaders as a quality shock that won’t break the bank – not only offer quality off-road performance, but they also offer the option to adjust the front of the vehicle’s ride height as well.

The zinc-coated Bilstein 5100s are a direct replacement for our 4Runner’s stock suspension. The front shocks (center) replace the stock units and simply re-use the front springs, while the rear shocks are just a direct swap.

Monotube vs. Twin-Tube
Bilstein relies on a monotube design for its 5100 versus a twin-tube setup. Twin-tube shocks are commonly used on trucks and SUVs to offer good all-around performance in what is typically a fairly cost-effective option. Monotubes tend to be a little bit more expensive (although not by much), but they are more often relied upon in situations where a higher level of performance is required because of their ability to more effectively dissipate heat and handle more powerful loads.

There’s far more to the conversation of twin-tube versus monotube, but in short, twin-tube shocks rely on two separate tube chambers, with the main center chamber featuring a piston that moves up and down through hydraulic fluid, while the outer tube serves as a reservoir filled with air, or more commonly nitrogen gas, to provide damping force as the hydraulic fluid flows in and out of the chamber. The fluid and gas in a twin-tube shock are not fully separated, and under heavy performance the oil can start to cavitate, or mix with the air to form air bubbles, which reduces its ability to provide consistent resistance and support for the piston as it moves up and down inside the shock body.

Here's a closer look at diagrams of a twin-tube shock (left) and monotube (right). Photo: Courtesy of Bilstein

A monotube shock, as the name denotes, still features fluid and gas but they live within the same single-cylinder space and are separated by a piston seal. The monotube design accommodates a larger piston and has additional space for more hydraulic fluid for the piston to move through. On the other side of that piston seal, gas helps absorb the force of the piston’s compression to provide damping force, and ultimately the valve assembly acts as one single unit. Thanks to the additional oil volume, heat can dissipate faster in a monotube shock and it is less prone to performance fade (due to the oil heating) in high-performance situations, like when off-roaders are powering through very bumpy terrain and the shocks are working overtime. The additional hydraulic fluid volume and larger piston essentially provides the monotube with a higher performance threshold.

These machined notches in the front Bilstein 5100s allows for ride height adjustment of our 4Runner in one of four settings: stock height, .85”, 1.75” and 2.5”.

Although we’d be installing shocks on our fourth-generation 4Runner, Bilstein actually offers its 5100 for multiple truck and SUV models, and each shock is tuned specifically for each vehicle. Bilstein relies on a digressive piston design in the 5100 to offer consistent performance in varying conditions. For added durability, it uses a Zinc coating on the 5100 shock body for added protection from the elements.

One of the features that off-roaders love most about the 5100s is the ability to adjust vehicle ride height, because these shocks eliminate the need for coil spring spacers and can lift the front end of coilover-equipped stock vehicles up to 2.75 inches on some applications (on our 4Runner the max height is 2.5”). The nose-down rake most stock vehicles have straight from the factory can be eliminated, or the truck or SUV can be lifted even higher for additional ground clearance and/or to accommodate larger tires.

The 5100s actually utilize the stock coils of your vehicle, and thanks to an adjustable circlip that supports the spring collar, you can select one of four height settings on the 5100 Series shocks. For our fourth-gen 4Runner, these height settings include: stock height, .85” of lift, 1.75”, or 2.5”.

This is a diagram of the Toyota 4Runner X-REAS system. We decided to remove it entirely in place of our Bilstein 5100 shocks.

The 5100s are a direct replacement part and the installation is something the garage mechanic, with the proper tools, can tackle in a few hours. For the case of our fourth-gen Sport Edition 4Runner, the job took just an extra hour or so because of an added obstacle: the X-REAS system. Toyota offered the X-REAS, or X-Relative Absorber System, as an option on third- and fourth-generation 4Runners or as a standard suspension offering on Sport models. The system uses lines to transfer hydraulic fluid from shock to shock to improve handling, and reduce body sway, in turns by transferring the oil to whichever corner needs it most. Since our 4Runner was purchased used with a decent number of miles on the odometer, we really have no idea how fresh or worn out the system is, but the servicing of the system requires the servicing of the shocks as well, so it’s not a cheap or simple fix or replacement.

There’s no electronic indicator of the X-REAS system in our Sport Edition 4Runner – the system functions independently with no driver input needed, though it does need to be serviced and/or replaced eventually. The hydraulic fluid carried from shock to shock is the system is fed via lines that are connected directly to the shock bodies. When removing the system, you’ll want to loosen the bolt to bleed out the fluid, and it will get a little messy so have a container ready to catch the fluid.

The good news is removing the X-REAS System is pretty simply, and there’s no real downside to doing so if you plan to replace the shocks with something like a 5100 (in fact, it’s pretty much necessary to remove). Just keep in mind you’ll need to replace the shocks at all four corners. The X-REAS system is only attached to the shocks and there’s no electronic connection to the computer, and the removal of the system won’t kick up any warning lights on the dash. The lines do contain hydraulic fluid that runs from the shocks and is distributed via center control absorbers (funny enough, manufactured by Yamaha), and it can be messy when you remove the system so keep a container for drainage close by.

Once the vehicle is securely resting on jack stacks and the wheel is off you can loosen the top of the shock (left) and the base mounting location.

Here we loosen the bolt connecting the upper A-arm bolt to the spindle.

The upper A-arm and the spindle will not separate easily, so having something like a 32-ounce hammer on hand for a few good whacks will help, or there are tools available to help pry them apart.

Once the shock is free you’ll need a spring compressor tool to remove the stock spring from the stock shock. If you don’t own this tool, many autopart stores will loan or rent them out, or you can pick up an inexpensive set from Harbor Freight or other retailer.

The Bilstein shock will reuse the stock spring and also the suspension support bracket atop the shock.

Here’s a comparison between the OE shock and the Bilstein. We only have the ride height set at the second setting to provide a little less than one inch of lift, but the 5100s can be set as high as 2.5 inches for our 4Runner.

The Bilstein 5100 is ready to install, but the tricky part is getting everything lined up properly.

After securing the base of the Bilstein 5100 on the lower control arm we used the jack to apply additional pressure on the lower control arm to connect the upper control arm to the spindle.

Although there are a few extra steps to install the Bilstein 5100 up front on our 4Runner, it is a direct replacement part so there’s no modification needed to the stock suspension system (except in our case we are deleting the no-longer-needed X-REAS system).

The rear shock replacement is a much simpler swap. The top mount is a little snug but there’s just enough room for a wrench to fit.

Even though we already drained and separated the X-REAS system up front, we realized as we disconnected the line from the rear shock there was still pressure in the line.

Once we disconnected the X-REAS line from the rear shock, we snipped the metal line that transfers the fluid from shock to shock and then removed the center control absorber (there’s one on each side of the 4Runner). We were surprised to see the part is actually manufactured by Yamaha.

Here’s a comparison of the stock unit and the Bilstein 5100. The rubber suspension bushing is the only part we’ll remove and reuse from the OE shock, though if yours is worn you’ll want to replace this piece.

Once the Bilstein is in place, some force is needed to line up the lower mount, and it’s in these instances where an extra set of hands can come in handy. Overall, the rear shocks are a much smoother installation process though.

After double checking the tightness of every bolt, we reinstalled the wheels and were ready for a test-drive. The Bilstein 5100s are an immediate improvement even on the highway, as our worn-out suspension was just too soft to provide a good all-around driving experience. The monotube Bilsteins provided some additional lift to reduce the nose-down stance of the 4Runner, and we appreciate the firmer ride the shocks provide. Off of the highway, the additional clearance (even though we only used the first lift setting) was immediately noticeable, and the firmer shocks help soak up bumpy terrain far better. The only slight downside for some might be a stiffer on-road ride. We notice the ride is a little stiffer on the highway, and our only gripe is the rear is just a hair stiffer than we’d like on some bumpy roads. Overall, though, the Bilsteins offer a great improvement in performance and were an easy way to lift the nose of our vehicle.

Whether needing to add additional lift to the front of your vehicle for added ground clearance or to fit larger tires, the Bilstein 5100 shocks are a great option to easily improve off-road performance and provide an alternative to coil spacer kits. If it’s a job you don’t care to tackle yourself, most reputable off-road shops can perform the installation for somewhere in the $200-$300 range, so even with the cost of the shocks it won’t break the bank to improve your vehicle’s stance and off-road performance in once shot.

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