ZoneControl® CR: Position sensitive damping with 3 compression zones and 2 rebound zones, controlled by 3 independent pistons:

• Compression (C): Provides superior bottom out control through a 2-stage, telescoping internal compression stop. This feature eliminates the need for an external hydraulic bump stop
• Rebound (R): Secondary rebound stop will dissipate spring energy and stabilize the suspension directly following a large compression event. The internal rebound stop will also eliminate harsh top-out events and the need for an external limit strap

The JCO is a hydraulic cylinder inside of the shock. The top most piston on the piston rod indexes into this cylinder which provides the 2 stage bottom out. The JCO piston has a bleed shim, preload shim, and standard valving. This means that the 2 stages are also velocity sensitive, so during crawling and low speed articulation it takes significantly less force to cycle through this compression zone.

The initial stage of compression zone is when the JCO piston contacts the hydraulic cylinder. This forces the volume of oil inside of the JCO cylinder to flow through the JCO piston. While this is happening the main piston is still active as well, the JCO piston is just adding to the damping effect of the main piston. This is the primary reason why the Zone Control shocks are technically not a bypass shock. Oil does not bypass the main piston to create the zones, the zones work in harmony with the main piston.

In the second stage of the JCO bottom out, the inner face of the JCO hydraulic cylinder bottoms out on itself which forces the outer shell to begin to compress as well. This flows significantly more oil through the JCO piston which creates the third and final compression zone.

-The Rebound Cut-Off zone is there to fully arrest any spring force that your primary rebound zone hasn't (or shouldn't) taken care of. There is a floating receiver attached ot the seal head assembly with a spring. That spring keeps it at the right position so the rebound zone engages in the perfect spot. The RCO piston lies beneath the main piston on the piston rod and engages with the floating receiver to create the final rebound zone. This piston also has bleed, preload, and main shims making it velocity sensitive as well.

This zone really helps after large compression events. Imagine you have just bottomed out your vehicle very hard and jumped it into the air. The tires have no resistance to hitting full droop really quickly, all that unsprung weight is moving away from the vehicle at a rapid rate of speed. Without this zone, all that force will increase until something stops it, whether it be a limit strap or some kind of mechanical binding. Because all that force is stopped right at once it transfers a ton of load into the chassis which can pull the vehicle down and whatever spring force is not dissipated will cause major issues when you land. With the RCO piston that leftover unwanted spring force is dissipated when the piston contacts the receiver that forces oil to flow through it.

Having this zone also allows the rebound valving to be soft enough to re-accelerate the unsprung mass very quickly and get lots of shaft speed over small inputs that keeps the tires on the ground, without blowing through rebound valving on large hits.

Bilstein uses their 60mm high flow digressive style piston in the 8112. This piston is digressive in design however it can produce any kind of valving curve desired; linear, progressive or digressive. The biggest benefit to this piston is that it is the only mass produced piston available in the off-road performance category with true directional bleed.

This spring and valve here directly above the piston in the photo above creates directional oil flow, allowing the bleed shim on both sides of the piston to flow through on compression events, but isolating the rebound bleed shim on rebound events. Rebound events are on average 3x the force that compression events are, so it makes sense that proper valving would require different amounts of bleed. The traditional way to do bleed is with holes drilled through the main piston which allows flow in both directions. This can make a vehicle excessively floaty and result in poor handling and ride quality overall.

The piston allows a best of both worlds where compression can be any valving curve you want, and you can still have a light digressive rebound curve which provides exceptional handling while retaining performance off-road when combined with the RCO. It also enables tuners to change any aspect of the valving curve desired, using bleed shims, preload shims, and check valves, in addition to the standard velocity sensitive valving shims other brands use.

The design idea of the 8112 coilovers specifically is to give the absolute best mix of on-road handling/drivability and off-road performance. As a comparison to a traditional bypass, the Zone Control system is purely additive. You have the base valving and valving curves, and the additional valving curves of the extra zones take over when you're using enough of your suspension to be out of the "ride zone". In contrast a bypass with external bypass tubes is pulling oil from flowing through the main piston, and relying on the reduced oil flow to create the ride zone feel. In this way the ride zone of the 8112s is fundamentally different.

It doesnt.

The 8112 Zone Control shocks are not designed to compete with normal shocks. These are designed to replace a coilover, bypass, air bump setup that has been custom tuned for the vehicle.

Low/High speed compression:

These adjusters effect another piston in the reservoir, this is the 4th piston in this system. These external adjusters have several advantages even regardless of adjustments.

-Reduces Cavitation. The original version of these were called "anti-cavitation valves" because they help maintain consistent pressure in the entire shock which reduces the formation of vapor bubbles.

-Adds heat into the shock where it is easiest to cool

Bilstein's DSA adjusters change your valving more than any other adjuster i have seen on the market. They offer several times more adjustment than a fox DSC would, which is a good and bad thing. With these adjusters specifically it's important to only do a click or 2 at a time, there is no need to fully bottom these out in one go like there is on other brands.

Low speed:
This adjusts low shaft speeds which are independent of vehicle speeds. You can be using the low speed circuit when traveling at very high speeds.

For instance if your vehicle has slight movements on the freeway at 70 mph you are likely in your low speed circuit. You can also use your low speed adjuster to dial in body roll, say you are exclusively driving windy mountain roads that day or you have added a lot of weight to your roof, you can adjust your low speed in to regain some stability.

Off-road you might find that your tires sidewall is not doing a good job of soaking up very small inputs, so you can adjust the low speed to increase that initial shaft velocity.

High Speed:

Just as with low speed, high speed is not related to vehicle speed. If you are driving offroad at 10 mph and drive over a giant rock you are likely in your high speed circuit. This adjuster controls more spirited driving than the low speed adjuster.

If your vehicle is bottoming out excessively at speed, you can turn the high speed adjuster in just a click or 2 to adjust that. f you have a performance suspension and you are driving at speed, your suspension should bottom out and you should be using the full stroke of travel to keep the ride as comfortable as possible.

The JCO adjuster has 10 settings using 1 full rotation of the knob.

This adjuster is changing how much force it takes to cycle through the final compression zones. After you have gotten your low speed and high speed adjusters adjusted you can focus on really dialing in your bottom out feel.

If you generally like the performance of the vehicle over all terrain but find on really large inputs it bottoms out very firmly, you can add in some more valving adjusting the JCO here.

A tricky thing with shock tuning is that too much and too little valving can feel similar, for this adjustment i recommend setting a gopro under the vehicle and seeing how much shock shaft you are actually using. Sometimes i find folks add too much JCO adjustment in, which is not allowing full travel on what is the roughest terrain you might hit. For that reason it's good to experiment with these adjustments, and if you get too far off the total number of turns and clicks is written on the shocks so you can always get back to baseline.

These shocks are the best OEM fit coilovers on the market, i often say "there isn't even a second place".

Our personal set of coilovers has 80k miles on them, have been above 320 degrees, and is still using original seals.

This technology has been around for a long time but within the past decade Bilstein has pushed it into the Off-Road aftermarket with glowing reviews. The owners of other shock companies in So Cal have purchased these to try and figure out how to improve their own IBP line.

All that being said these shocks are not for everyone. This shock package will let you out-drive your vehicle, and should be taken seriously. If you're considering these you'll want to look at all the normal structural upgrades like spindle gussets, UCA dual shear, cam tab gussets, etc.

We are the only shop that rebuilds, tunes, and does warranty work on these shocks. We have installed and tuned hundreds of these, possibly more than any other dealer combined.

With over 5 years of tuning experience with this platform we have valving setups that account for additional weight, driving styles, and specific vehicle use cases.

We take the best and make it better.