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Budget, Better, and Best Parts For Your Rig’s Suspension

Posted in How To: Suspension Brakes on May 1, 2012 Comment (0)
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When it comes to building the suspensions under our rigs, we’re faced with many choices when choosing parts. As a matter of fact, we dare say that there are more choices now than in the history of four-wheel drive. This is good, but it can create a dilemma for us wheelers. Questions arise about the pros and cons of these upgrades and whether they’re a good fit for a specific type of off-road travel and/or vehicle. Naturally, cost is also a major player in the equation as well.

Hydraulic bumpstops replace the fixed units and allow for smooth, controlled, tunable suspension uptravel and downtravel. Here you can see a Light Racing JounceShock installed on our project Trailhugger Hummer H3

To answer some of these questions, we’ve listed a few of the most commonly modified suspension components and we’ve split them into budget, better, and best. We’ve also listed basic information for each as well as pros and cons. Finally, since we always have something to say, Editor John Cappa, Technical Editor Sean P. Holman, and Senior Editor Ken Brubaker have weighed in with their preferences and thoughts in each category.

Bear in mind that how these are graded (budget, better, best) may be open to interpretation. For example, if you have a pickup truck that’s used to plow snow, you probably don’t need race-ready bypass shocks. Even though they’re arguably the best in the shock world, their numerous features would probably be overkill on a plow truck, and a quality set of monotube or twin-tube shocks may work just fine. On the other hand, if you use your “other” rig to bomb across the desert, bypass shocks may in fact be the best choice.

The bottom line is that hopefully this info will help you determine what’s best for your rig based on how you use it, and your budget.

Bumpstops
Lowdown: Bumpstops control how much upward travel your suspension can have. If your rig didn’t have bumpstops, the suspension could over-compress when you hit a bump and this would wear out the springs and potentially allow damage to the shocks and other components. A bumpstop isn’t just a “stop” though, it also offers additional suspension damping as it compresses.

Budget: Rubber
These bumpstops are what’s usually installed at the factory (though there are some other materials used nowadays). Rubber bumpstops are inexpensive and durable. They function and hold up well to direct force and most have a tapered shape that provides some damping as it is compressed. Many aftermarket lift kits simply offer a system to lower the factory bumpstops to compensate for suspension lift. The downside to rubber bumpstops is that they can be adversely affected by oil (which can cause them to soften) and after a few years rust can cause the bumpstop to part ways with its mount. It’s also worth noting that they dissipate energy into the suspension rebound, which has to be damped by the shocks.

Pros: Inexpensive, adequate for general low-speed wheeling

Cons: Subject to damage from oil, rust can damage the mount, they dissipate energy into the suspension rebound

Better: Polyurethane

Often considered a step up from rubber, polyurethane bumpstops are available from a number of aftermarket companies. They often follow the same design characteristics as rubber, but they can also be found in progressive-style, which offers light damping and then stiffer as the bumpstop compresses. Poly bumpstops have great longevity, are inexpensive, and more oil resistant than rubber. They’re stronger than rubber and have less deflection under load. However, they’re typically stiffer than rubber and they can crack under heavy compression. Like a rubber bumpstop, polyurethane bumpstops dissipate energy into the suspension rebound, which has to be damped by the shocks.

Pros: Oil resistant, long life, inexpensive

Cons: Can crack under heavy compression, stiff, dissipate energy into the suspension rebound

Best: Hydraulic/air

Born of desert racing, these are basically small shock absorbers that replace the stationary bumpstop. Most often they’re filled with shock fluid and nitrogen gas. They gradually damp the final segment of suspension uptravel and work great to absorb the forces of high-speed off-road travel or jumping where full suspension uptravel is the norm. They also help to damp downtravel, too. These bumpstops are typically adjustable so they can be fine-tuned for your application. They work very well in both solid axle and IFS/IRS applications. Most require welding to install the mount, but some use bolt-on mounts. Hydraulic bumpstops are on the high end of pricing in the bumpstop world.

Pros: Gradual damping of uptravel and downtravel, tuneability

Cons: Expensive compared to fixed bumpstops, more labor intensive to install

Staff weigh-in
Cappa: In most cases the factory rubber or EVS foam bumpstops are plenty adequate. Urethane bumpstops are often too harsh and rigid. They can crush and tear if designed poorly. Hydraulic/air bumps are able to absorb a lot of energy but they are best suited on 4x4s that see a lot of high-speed use, hard impacts, or airtime. The Daystar Stinger is a good budget alternative to full hydraulic bumpstops.

Holman: For most wheeling needs, I am a fan of the factory bumpstops. They are usually durable, compliant, and adequate, even with heavier wheels and tires. Once you mix in some speed, hydraulic bumpstops are hard to beat.

Brubaker: For me, hydraulic bumpstops are mandatory on the front of IFS-equipped rigs where the lower A-arms sit on or near the factory bumpstops at rest (like on late model GM trucks and SUVs). In this situation, adding hydraulic bumpstops significantly improves handling both on- and off-road because instead of traveling into fixed bumpstops the uptravel is gradually damped by the tuned hydraulic bumpstops. I was skeptical of hydraulic bumpstops price-versus-return until we installed Light Racing JounceShocks on our project Trailhugger Hummer H3. The improved handling and ride both on- and off-road was extraordinary. I run rubber bumpstops on my solid-axle rigs and they work fine, but I wouldn’t hesitate to install hydraulic bumpstops given the opportunity.

Shock Absorbers
Lowdown: Shock absorbers control unwanted motion through a process called damping. They convert the kinetic energy of suspension movement into thermal (heat) energy, which is dissipated through the shock body. Without shocks your rigs springs would bounce up and down after hitting a bump (taking your rig with them) until all of the energy put into the springs by the bump was used up.

Reservoir shocks help to offer even cooler operation under hard use. They’re a bit more expensive than a non-reservoir shock, but if you routinely travel over harsh terrain at speed they’re worth the money.

Budget: Twin-tube

A step up from the stock shocks on your rig (which were designed for your vehicle in stock form) is an aftermarket twin-tube shock. These shocks are usually pressurized with nitrogen gas, which is mixed with hydraulic oil. These shocks are inexpensive and scores of these types of shocks are available in the aftermarket. Most use automatic velocity-sensitive valving. They’ll typically have a larger shock body, piston, and rod diameter than the factory shocks so they’ll hold up better off-road. Many companies offer twin-tube shocks valved specifically for a given vehicle, too. The downside to these shocks is that under hard use they can suffer aeration/foaming, which is the cause of shock fade.

Pros: Inexpensive, beefier components than stock

Cons: Can aerate/foam during hard use, leading to shock fade

Better: Monotube/reservoir

Like twin-tube shocks, monotube shocks are typically beefier than factory shocks. Unlike twin-tube shocks the hydraulic oil and nitrogen gas are in separate chambers separated by a floating piston and this design helps to effectively dissipate heat and eliminate cavitation, which in turn reduces shock fade during hard use. They also dissipate heat better because they only have one wall in the shock body, unlike a twin-tube shock. There are a number of monotube shocks available in the aftermarket and some offer manual adjustment of the valving while others do it automatically. Monotube shocks cost more than twin-tube shocks because they cost more to manufacture. Reservoir shocks were designed primarily to prevent the aeration/foaming of the shocks hydraulic fluid during hard use. The addition of an external reservoir allows for more fluid, thus cooler operation. Reservoir shocks come in two varieties, remote (where the reservoir is mounted separately from the shock body) and piggyback (where the reservoir is mounted on the shock’s body). Reservoir shocks are great for extended hard use where the suspension is cycled quickly for long periods of time. Reservoir shocks are more expensive than monotube shocks and they take up more space than a standard monotube or twin-tube shock.

Pros: Resistant to shock fade, some are rebuildable and adjustable

Cons: Generally stiffer than twin-tube shocks (though they can be revalved to lighten damping), reservoir shocks are more expensive and require more room to mount

Best: Bypass

Another product we can thank the racing community for are bypass shocks. They have adjustable metering valves for changing the rebound and compression of the shock. In addition to being velocity-sensitive like a standard shock they’re also position-sensitive, meaning the rebound and compression can be set to be softer initially and then provide more damping as the piston travels through each different “zone.” Like a reservoir shock, bypass shocks require more mounting space. The bypass tubes can run either externally or internally. Bypass shocks are expensive.

Pros: Rebuildable, mega adjustability

Cons: Expensive, more mounting space is needed, the check valves emit a clicking noise as they open and close, complex, more maintenance

Staff weigh-in
Cappa: They may look cool, but you really only need to consider bypass shocks and their complex and unlimited adjustability when you get into 14 inches or more of vertical wheel travel. They are built for high-speed and competition use. Monotube and reservoir shocks can provide more than enough damping for most 4x4s. They dissipate heat better than twin-tube shocks and in most cases the valving can be changed by disassembling the shock. However, a twin-tube shock is plenty sufficient for an everyday, daily-driven 4x4.

Holman: For my money nothing beats a well-valved monotube with a reservoir. A properly set up monotube with a reservoir will work better or as good as any shock 95-percent of the time. Sure, bypass shocks are a nice luxury if you have the space, money, and time to tune, but they just aren’t necessary for the average, and even above average, 4x4. Plus, they can be noisier and require more maintenance than a standard monotube shock.

Brubaker: There’s not a lot of high-speed desert terrain here at the Four Wheeler Midwest Bureau in northern Illinois. However, there are miles of washboard gravel roads and driving them at speed can heat up shocks and cause them to fade. I’ve heated up twin-tube shocks to the point of fade during sustained high-speed driving on these gravel roads, but so far I’ve never had a problem with monotube shocks overheating. For the money, monotube shocks are more than adequate. However, I’ll spend the extra money for a reservoir shock just to get that extra margin of cooling.

Control Arm Ends
Lowdown: Your rigs control arms link the axle to the vehicle and they help keep the axle in its proper position. Typically a vehicle with a link-type suspension has a pair of upper and a pair of lower control arms. The control arm ends are what allow the control arms to pivot, thus allowing the suspension to articulate. If they didn’t allow movement, the suspension wouldn’t be able to articulate.

There are a number of control arm joints in the aftermarket and they come in a variety of styles. This X-Flex unit from Rough Country Suspension offers up to 35 degrees of pivot range and the joint is rebuildable.

Budget: Rubber bushings
Most factory suspensions utilize rubber bushings in the control arms. Like rubber bumpstops, they’re inexpensive and durable. They’re also great at absorbing road vibration so it isn’t transferred to the cabin. Like rubber bumpstops, oil can impregnate them and make them mushy over time. Rubber bushings have design limits that flexy suspensions and heavier wheel/tire combinations can exceed.

Pros: Inexpensive, durable, they limit road vibrations to the cabin

Cons: Oil can make them mushy over time, they can be overwhelmed by suspension flex and heavier wheels/tires

Better: Polyurethane bushings

Available from a number of aftermarket sources, polyurethane bushings are stiffer than rubber and the result can be better on-road handling. They also typically offer a longer life than rubber bushings and they resist oil. Polyurethane bushings are included in many aftermarket control arms. They need to be greased to seal out water and dirt and they tend to transfer vibrations more than rubber bushings. They’re also prone to squeaking if not properly lubed and they can inhibit suspension flex due to their stiffness.

Pros: Inexpensive, long life

Cons: Need to be greased to eliminate squeaking, stiff, transfer road vibration more than rubber

Best: Joints/spherical rod ends

There is a wide variety of joints and spherical rod ends available for control arms, and they differ widely in construction and strength. One thing they all have in common is that they offer more movement than a standard rubber or polyurethane bushing setup and this will help improve suspension flex. Some joints incorporate urethane or nylon bushings to decrease road vibrations being transferred to the cabin. Also, many of these joints are greasable and rebuildable. Quality spherical rod ends are very strong but they don’t typically use a rubber or urethane bushing, hence they transmit vibrations to the cabin. Most rod ends are not greasable or rebuildable.

Pros: Strong, flexy, many joints are greasable and rebuildable, quality spherical rod ends are very strong

Cons: Both joints and quality spherical rod ends are more expensive than rubber or polyurethane

Staff weigh-in
Cappa: I’m actually a fan of factory rubber control arm ends. In a typical 4x4 application nothing seems to last as long as the factory rubber parts and they are maintenance free. Polyurethane control arm bushings will last nearly forever, but they can be noisy, harsh, and limit movement. They also need to be greased often. Spherical rod ends are best suited in racing environments where they are checked and replaced regularly. On a daily driver you’ll be lucky to get a few thousand miles out of a rod end before it becomes worn and needs to be replaced. If you’re looking for an aftermarket joint with lots of articulation, make sure it’s greasable to keep contaminants out. Currie Johnny Joints or Rubicon Express joints are good options.

Holman: On my links, I prefer factory rubber. The OE engineers have the durability and flexibility nailed and the OE bushings are tuned to keep NVH to a minimum. If you need more flex, Currie’s Johnny Joints are probably the next best thing. Don’t be afraid to run Johnny Joints on the axle end and rubber on the vehicle end. It gives you the best of both worlds: flex and NVH control.

Brubaker: Flex isn’t a big must-have for our work trucks here on the farm. Hence, I just don’t need a fancy, high-tech joint on the ends of my rigs control arms. Nor do I want the hassles of a rod end. I like the no-maintenance, insulating qualities of rubber bushings. I’ve never had a problem with them after years of driving in mud, snow, salt, manure, and rain.

Conversion
Lowdown: If you’re thinking of going whole hog and converting your suspension from IFS or leaf-springs, you may have considered a coil/shock setup, air shock setup, or coilover setup. Each has its own benefits and drawbacks, and its own price point.

One of the options for a suspension swap is coilovers. Everything you need to suspend and damp your rig is contained in one package. The beauty of coilovers is that if you’re converting from another system you’ll only have to fab two mounts per coilover.

Budget: Coil/shock:

This system is as old as dirt and it has been used on numerous rigs over the years. This system is low buck compared to other options and can be done even cheaper by using a used pair of coil springs. It is a bit labor intensive to install as spring pads and shock mounts must be fabricated and installed.

Pros: Inexpensive, can be designed to provide lots of articulation

Cons: You’ll need to fab multiple mounts, it won’t wow your friends like air shocks or coilovers

Better: Air shock:

About half the price of coilover shocks, air shocks (also known as emulsion shocks) not only control ride height but also damp the ride. Typically, these shocks have an emulsion of oil and nitrogen in the same cylinder and there is no internal floating piston so they must be mounted as close to vertical as possible. This is about as simple as it gets when it comes to suspension. They’re small in diameter, lightweight, adjustable, rebuildable, and revalvable. The downside is that they don’t have much weight carrying capacity, you’ll need a high-pressure nitrogen source to adjust them, and they require a sway bar to counter their little natural roll resistance.

Pros: Simple, adjustable, relatively inexpensive

Cons: Low weight carrying capacity, you’ll need nitrogen to adjust them, plan on a sway bar, can heat up and fade during hard use

Best: Coilover:

It’s a shock and spring packaged together. You can get ‘em with or without a reservoir or with an emulsion shock with a single spring or multiple springs in the case of dual- or triple-rate units. Coilovers have many benefits including an incredible amount of adjustability between the springs, shock valving, and adjustable top spring seat. They are large in diameter, however, so you’ll need ample room for mounting.

Pros: Spring and shock in one package, gobs of adjustability

Cons: Heavy, large in diameter

Staff weigh-in
Cappa: Running a coil and shock is inexpensive if you are building your own suspension. However, building mounts for both can be complex and can take up a lot of space. Air shocks are compact, easy to mount, and lightweight. They provide nearly unlimited spring adjustability (nitrogen pressure) but they are best suited on lighter 4x4s that don’t see much high-speed use. Once they heat up they become much less useful. A coilover is compact, easy to mount, and provides some spring adjustability in the form of different rate and length coils and shock body adjusters. Coilovers can be made to work in both high- and low-speed applications. The valving is adjustable but the shock needs to be disassembled to change it. Coilovers are generally a little heavier than a comparable air shock and a lot heavier than a stand-alone coil and shock.

Holman: Make mine coilovers. They are easy to mount, compact, and can be tuned specifically to the 4x4 and driver’s preference.

Brubaker: Coilovers, please. I like the fact that everything is contained in one package and there are only two mounting points per coilover. They can be tuned specifically for the vehicles intended use both with spring rate and shock valving. For my daily driver/work truck I’d choose a single-spring setup with a reservoir shock.

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