Over the past decade suspension technology has evolved greatly. What was once reserved for race-only off-road applications we are now seeing bolted under daily driven 4x4s. One of the biggest areas where we have seen major advancements is in shock absorbers, with the latest push being internal-bypass shocks.
A great example of this can be found with Old Man Emu by ARB’s new BP-51 internal-bypass shocks for the 2005-2015 Toyota Tacoma. The concept behind the shock was to create a position-sensitive absorber that could balance the off-road needs of hardcore enthusiasts while retaining the plush on-road ride OME is known for. Your basic shock functions by passing fluid (oil) from one chamber to another. To control the shock’s travel (compression and rebound), a piston fit with valves on both sides moderates the speed at which the oil passes.
OME’s BP-51 shocks, however, are built with four compression and two rebound channels, which allows the fluid to bypass the valve piston in a given zone. Since the shock is position-sensitive, the damping force varies depending on where the piston is located. This design allows the shock to easily absorb everyday road imperfections and minor bumps at ride height, so you don’t get the jarring effects of an overly stiff shock. As the shock cycles further into the higher compression zones, the resistant increases, allowing the shock easily handle rougher off-road conditions. Since the BP-51 was also built with external compression and rebound adjusters, you can fine-tune the suspension to fit your driving style and build.
We wanted to know how all of this technology worked in the real world, so we tossed our 2008 Tacoma Double Cab on the rack at Low Range 4x4 in Wilmington, North Carolina, and installed OME’s latest complete second-gen Tacoma suspension. Bolting on in just a few hours, we have been able to log a few thousand miles of on- and off-road testing. So how did it all work? Read on.
It can be a little challenging to visualize exactly what is happening inside of the BP-51, so we got OME to send us a cutaway of the shock. The small external valleys you see running between the exterior wall of the shock and the piston cylinder are the bypass channels. By having multiple ports for the fluid to bypass, OME was able to create a position-sensitive shock that increases damping control as the shock moves through its phases of travel.
The BP-51 has 10 levels of compression and rebound adjustment. Compression controls the upwards movement of the shock, while rebound slows the downward motion. By increasing the adjustment, you are raising the stiffness of the shim and restricting the bypass oil flow. Since this can be done on the vehicle using the provided tool, it doesn’t take much to change the handling of the vehicle.
Up front, the coilover assembly is fit with a 600-pound coil rate. While you can adjust the coil preload and ride height, we found the as-shipped setting to give us 2 1/2 inches of front lift. Our Tacoma is fitted with an aftermarket winch bumper and portly skidplate system, so you may find you’ll need to adjust yours to accommodate any aftermarket components you may or may not have.
Since our Tacoma was equipped with Icon Vehicle Dynamics Uniball upper control arms, we only needed to detach our sway bar endlinks from the steering knuckle to remove the old shock assembly. OME uses the existing mounting holes on the top of the strut tower and stock bolt to hold in the new shock. Note: Aftermarket upper control arms are not required with the BP-51 shocks. We simply like the Icons for the increased range of motion and strength upgrade over the stock uppers.
To increase oil cooling as well as shock travel, the BP-51s were fit with remote fluid reservoirs. These compact cylinders come with a nitrogen charge, which keeps pressure on the piston that separates the fluid from the gas. Another plus: The BP-51s are completely rebuildable.
Out back, we are running OME’s Dakar leaf-spring pack, which netted us around 3 inches of lift. The complete replacement spring pack also included new polyurethane bushings to tighten up the rear of the truck.
The rear BP-51s are fit with rock protectors to protect the shocks shaft. Just like the front, the rear shocks are completely adjustable. To fit them on the truck, OME includes shock brackets that space out the larger-diameter shock. This requires a little drilling but is not difficult.
Both front and rear shocks are side-specific. Each comes with a bracket to secure the remote reservoir out of the way.
Tires & Wheels
For tires and wheels, we opted for a 285/75R17 Nitto Trail Grappler and mounted them on a set of 17x8 matte bronze Konig Countersteer Type X wheels by FN Wheels. We’ve had a few vehicles on Trail Grapplers, and the approximate 34x11 dimensions of our new mud-terrain radials fit our build perfectly. The 4.1-inch backspacing on the hub-centric FN Wheels meant that we were all good for clearance. Note: Our fenders and cab mount were already trimmed prior to this install; some minor trimming may be required for you to replicate our setup.
We have a little over half a year of testing on our current setup. Initially we ran the manufacturer’s suggested compression and rebound settings on the shocks, but have since modified the setting to better fit our needs. There is no question that the adjusters work. In fact, we suggest only changing the setting two clicks at a time. The rear springs are a touch on the soft side, but we love the ride quality they provide. If you tow or frequently load down the bed of your Tacoma, the add-in OME overload springs will probably be a good option for you. The front end feels incredibly tight and controlled. The coil rate is well suited for those with aftermarket skids and bumpers, so don’t fret if your Tacoma has some extra noise weight. Overall, we are extremely pleased with the ride quality both on the road and off.