Choosing new shocks for your truck is one of the most daunting challenges out there. Everyone wants to keep their truck as comfortable as possible, but wants control of that wallowy land rover ride. Your springs and your shocks play a major role in ride quality. We talked about springs in another article so now we will look at shocks.
Who makes shocks for my truck?
There are several manufacturers of shocks for our trucks. Some of the more popular brands are Bilstein, Old Man Emu (ARB), Ironman, and Rancho. Bilstein are available through many outlets in the country as are Rancho shocks. Old Man Emu generally have to be ordered through one of their distributors here in the us or custom off-road shops. Ironman suspension seems to be distributed in the US only by Land Rover. There are certainly other shocks that will fit your vehicle. Some from companies like DeCarbon are excellent quality pieces but are not recommended because they are hard to find in the US, others Like Monroe, Koni, etc, are not really designed for the rigors of off-roading. Now having said that, some companies DO make off-road specific shocks (such as Fox), but their shocks are intended for racing and at about $200-250 a PIECE, they are beyond the scope of this article.
Will they make my truck stiffer or looser?
The woodhead shocks that come on our vehicles are really not suited to the job once we start taking these vehicles off-road. Some would argue that their on-road performance leaves a lot to be desired as well. Changing shocks will surely bring about a change in handling, but not always the change you might expect. Choosing a high pressure shock like the Bilstein, WILL stiffen your ride, but it is also compliant, giving over bumps and undulations. If you are using stock springs and just want to add some control to your road driving, this may be the way to go. Low pressure shocks such as the Old Man Emu are designed to be mated to uprated springs. These shocks are very compliant and REALLY soak up the bumps well, but they rely on the springs to keep the car from rolling in the corners. So the question here is, are you keeping your stock springs or replacing them with uprated units? You will have to make your shock purchasing decision based on that.
What’s shock valving all about?
Since shocks move gas or liquid around inside themselves at certain rates to provide damping, it stands to reason that the faster the medium moves in the shock, the quicker the shock will compress or extend. Usually the compression and extension rates are very different. The reason is simple. When traveling down a road and encountering a bump, you’d like the wheel to deflect as quickly as possible so as not to upset the balance of the vehicle. This deflection is handled by the spring in large part. The softer the spring, the faster it deflects. You really don’t want the shock getting in the way of this because it would simply act like you added a stiffer spring. However, once the wheel deflects and that energy gets stored in the spring, you don’t want it springing back very quickly so you DO want the shock to slow it down. This is why compression valving on a shock is ALWAYS less than expansion damping. So how do you know what valving is correct? It’s basically a matter of looking at your spring rates. If we assume you have a spring with 100 LB/in of rate, and you typically encounter 2-5” bumps, you’d want a shock that could damp down that force. 5” of deflection x 100 LB/inch would give us 500 pound force inches of force. Or 56.49 Newton-meters in the international lingo. If we make this somewhat more realistic and use a 250 pound spring like you might find in a Land Rover, we’d then have 5” of deflection x 250 LB/in or 1250 pound-force inches or 141 Newton meters. If we use the vehicle off-road then we have to factor in that the spring may be compressed fully and then we would have to calculate based on an real-world spring having about 9” of compression. Using our 250 LB/in spring we would end up with 2250 pound force inches or 254 Newton meters.Now we would go look for a shock that offered about 50 Newton meters of compression force (75-100 if we wanted to remove the sway bars) and expansion valving around 250 Newton meters. This assumes that the shock will be mounted vertically on the axle. If the shock will be mounted in a canted fashion, allowances must be made. You’d be wise to add a 10% stiffer shock for every 20 degrees of cant. You can now go to a custom shock manufacturer armed with your proper valving needs. Or you can take a visit over to Eshocks, and have a look at the off-road shock offerings from Bilstein and determine what might meet your needs.
What's the difference between high pressure and low pressure?
Other than some special shocks which contain air for cushioning, almost all shocks contain some type of oil to control ride. That oil is moved up and down in the shock as we go over bumps through valves that let the oil flow at various rates. The faster the oil flows, the “softer” the shock feels. Although this is a gross simplification, it gets the point across. As we go over a LOT of bumps (think of washboard), the oil in the shock is moving very rapidly and building up heat. If the oil gets hot enough it will begin to boil (yes it does happen). When this happens, air bubbles form in the oil and it begins to lose its ability to damp out bumps and vibrations and we get a rough ride. This is called “shock fade”. There are a few ways to combat this. The first is to use more oil. The more oil we have, the more volume we have to disperse heat. When you see shocks that have extra canisters, sometimes referred to as reservoirs, this is what they are doing. The other approach is to use higher pressure in the shock. The higher the pressure, the higher the boiling temperature. Seems great, why doesn’t everyone do that? Well two reasons. First is that pressurizing the oil in the shock raises the cost in a HURRY. Second, oil at pressure is more difficult to move from place to place in a controlled manner. This is why high pressure shocks tend to ride much firmer than their low pressure counterparts, but fade less. Bilstein makes a huge deal about this, and it is important if you are pounding off-road at speed, but most of us are going 15-20 mph max off-road not 130.
What length do I need?
The easy answer is that it depends. Assuming that you will keep your stock springs (and brake lines) you can get the model # you need right from any of the manufacturers. Things start to get more interesting if you decide to change springs. Why you ask? Well, shocks operate in a range of motion. They are generally designed to operate best in the middle of that range. Most shocks give a little easier when they start to compress from normal ride height, offering a nice soft ride. As they compress a little more, they get progressively more stiff to keep you from bottoming out. If you use a shock too short for your application (like if you use longer springs with stock shocks), you will stretch the shock more than normal, and it will take longer for the shock to reach its stiff section. This may result in a ride that is too soft. On the other hand, if you choose a shock too long for your application, you will be riding with it compressed more than normal, giving you a non-compliant ride. If you use shocks that are FAR too long, you will also run into other problems such as bottoming the shock when you go over large bumps, or pulling your brake lines apart because the long shock will now allow the axle to droop much further than the old unit. Fortunately for us, many people have made these same modifications.We will compile some shock lengths in tables. The following tables are available: Rancho, OME, Bilstein, Fox.
How do I install them?
Installing shocks in a Land Rover is not a terribly difficult job, many people have done it, but it does require some basic tools, some strength, some good penetrating oil, and a lot of patience.