Articulating Ideas - Suspension Theory, Tips & TricksPosted in How To: Suspension Brakes on November 29, 2013 0) (
Modifying your vehicle’s suspension is an integral part of the off-road hobby. Whether you just need a slight lift to manage the local hunting-camp backroads, or a long-travel setup for legging through boulders, tuning your rig’s suspension to fit your needs is easier than ever. From control-arm lengths and shock valving to bumpstops and sway bar disconnects, there is an array of components and factors to consider when tuning your vehicle. Collectively, the magazine staff has a decade’s worth of suspension building and testing experience. Like many of you, we have learned the easy and hard way as to what works and what doesn’t. To get a better idea of what each of us has learned over the years, the crew weighed in on some of their favorite and not-so-favorite suspension setups.
I like to keep my 4x4s low. Unless you’re building a 4x4 to bash over rough terrain at a significant speed, you don’t need a ton of uptravel on the suspension of your 4x4. This is especially true if you only crawl at slow speeds. You might even consider having your suspension nearly rest on the bumpstops. The lowered center of gravity will make the rig more stable on sidehills and climb ledges better.
I prefer stiffer leaf springs if I’m running a spring-over configuration. Don’t go nuts with overly flexible leaf-spring packs. Leaf springs that are too soft and offer too much travel cause numerous other issues such as handling quirks, steering linkage problems, driveshaft binding/failure, axlewrap, and more. Firmer springs are better at controlling axle movement and driveline torque. It’s true that firm springs may allow a tire to lift in some situations, but that’s why we have lockers and other traction adding differentials. Letting a tire dip down into a large hole can often create more problems for both leaf-spring and link-type suspensions than if the tire is simply carried airborne over the hole.
There is more to your suspension than springs and shocks. The tires and wheels are an integral part of a 4x4’s suspension system. I always run the smallest diameter wheels I can reasonably fit on my 4x4s. Big wheels are heavy and are a detriment to suspension, acceleration and braking performance. More tire sidewall will cause the 4x4 to handle less crisp, however the benefits of a taller sidewall include a smoother ride and less shock-load stress on wheel bearings, steering parts, and other suspension and axle components.
I compensate for firmer springs on my 4x4s by significantly lowering the air pressure in my tires off-road. With beadlocks, most vehicles can get by with about 8-15 psi on a radial tire and 2-10 psi on a bias-ply tire with a sturdy sidewall carcass. The deflated tires envelop obstacles and not only offer a smoother ride over rough terrain; they provide improved traction and flotation in mud and sand.
Most 4x4s don’t need any more than about 10 inches of total wheeltravel (measured at the bumpstops), unless you’re speeding across the desert regularly, jumping your 4x4, or entering the local RTI ramp-champ competition. Keeping your suspension travel limited will improve the overall versatility, performance, handling, and reliability of your 4x4. The jaw-dropping flex of the RTI ramp champ at the fairgrounds may make for a cool photo, but it’s never the best trail truck. Use proper antisway bars, limiting straps, and bumpstops to keep coil springs from rattling loose and falling out of their buckets, shocks from topping and bottoming out, driveshafts from binding and separating, and tires from rubbing and being cut on the inner fenders.
Here in northern Illinois at the rural Four Wheeler Midwest Bureau, our most prevalent obstacles are deep snow, mud, and water. The commonality of these three things is that to get through ’em in a 4x4 requires decent ground clearance. Low ground clearance just doesn’t work. For example, I’ve had to dig quite a few un-lifted 4x4s out of the snow and mud because they didn’t have enough ground clearance to keep the belly of the rig from auguring in and stopping the vehicle cold. And when it comes to water, the enemy of a 4x4, keeping the liquid away from the engine’s air intake is a tad important. For this reason I will almost always install a lift under my rigs. However, I’m a fan of a low center of gravity, so I prefer a mild lift (four inches or less) to create more ground clearance while allowing for a taller tire to move the axles further up.
Remote Reservoir Shocks
Modern shocks are pretty amazing. Nonetheless they can be overworked to the point that they heat up and fail to do their job correctly. My most recent experience was overheating the shocks on a fullsize SUV on a rough desert trail, which resulted in an almost complete failure of the shocks. Eventually, I had to stop driving and let them cool. This is one of the reasons I’m a fan of remote-reservoir shocks, which run cooler in harsh environments resulting in less chance of fade. Further, rigs with larger-than-stock tires can also benefit from remote-reservoir shocks. I’ve been running remote-reservoir shocks on the Four Wheeler Dodge Power Wagon for the past year or so and they’re awesome, whether driving on washboard gravel roads, blasting down dirt trails, or maneuvering down rough paved roads.
I’m a fan of rubber suspension bushings. It’s impressive how flex joints and spherical rod ends help to increase suspension travel, but I don’t want the hassle of rebuilding or replacing said parts, which is common and can be pricey. Besides, I don’t need a super flexy suspension under my work-centric 4x4s. Additionally, all of my 4x4s are used like pack mules. I have enough to deal with keeping my old plow rig plowing and my tow rig towing without adding a clunking or squeaking suspension pivot point from a worn-out joint or rod end to the list. I also like how rubber bushings absorb shock and vibration better than most other options, including polyurethane. Heck, my 4x4s still have the original rubber bushings in their suspensions, and they seem to be just fine.
I was skeptical of Light Racing’s JounceShocks, which replace standard bumpstops with what is basically a small shock absorber, until I tried ‘em. I was worried that they’d be too soft or too hard and I’d have to spend a bunch of time messing around with the pressure to get ‘em right. I’m not a tinkerer. I have no patience. Besides, on my application, installing JounceShocks meant cutting off the factory bumpstops, which is a no-turning-back mod. Turns out, I had no reason to worry. The 4x4 I installed ‘em on was a late model GM IFS rig and on this particular rig, the lower A-arms sat on the bumpstops at rest. This meant that the A-arms uptravel was damped by fixed bumpstops. I replaced the bumpstops with the Light Racing JounceShocks and the perfectly-pressurized units controlled uptravel (and downtravel), which utterly transformed the handling of the rig for the better. To this day, it is one of the most functional and impressive mods I’ve ever made to a suspension.
Air Helper Springs
Confession: I’m not a fan of air suspension. However, I love using aftermarket rear suspension air helper springs for towing. Firestone Industrial Products offers a number of options like the Ride-Rite, which mounts between the frame and suspension of the rig. Most kits are inexpensive, simple to install, and easy to use. Air helper springs won’t increase your rigs towing capacity, but they will level and stabilize the vehicle. Heck, Firestone even offers applications to lift the front of a rig to help offset the weight of things like a snow plow. I’m a minimalist, so instead of adding a compressor and controls I typically run the air lines to the nearest end of the vehicle where I can manually fill each air spring prior to towing. When I’m done, I deflate ’em to the recommended pressure and it’s like they’re not even there.
Shocks can absolutely make or break the ride quality and performance of your 4x4. I’ve had vehicles that rode horrible, and after swapping on a set of properly-valved shocks, the rigs were completely changed. I like to go fast off-road from time to time, but don’t want my vehicles to be overly tall to accommodate the gobs of uptravel required for high-speed wheeling. This means I need a versatile shock that is soft enough to handle the small dash-rattling bumps, but stiff enough to keep the shock from blowing through on the big hits. Bypass shocks are great for this.
I’ve noticed more companies are moving towards internal-bypass shocks, which can be easier to package and fit over a traditional double- or triple-bypass shock. You may not think you can take full advantage of a bypass shock, but the reality is bypass-shocks are no longer a race-rig-only absorber. Internal-bypass shock technology is one of the key attributes that allow vehicles like the Ford Raptor to perform so well off-road and maintain excellent highway handling and ride characteristics.
It’s also worth mentioning compression-adjuster shocks here as well. Over the years I have toyed with many of the compression-adjuster shocks available from the aftermarket, looking for a nice range of adjustment as most claim. Unfortunately, there hasn’t been much consistency from one company to the next. Some compression adjusters move from way soft to firm-ish, while others are overly firm at even the lowest setting. Getting the right shock for your 4x4 may take some time, testing, and trial and error, but once you have the correct valving to fit your needs, the reward will be well worth the trouble.
I am a fan of multilink suspensions, especially in the front of a vehicle. I’ve used three-, four-, and five-link setups under a variety of my rigs and found that the four- and five-links (four links with a track bar) work the best for my needs. My least favorite setup is a triangulated three-link, as each version I’ve tried flexed great, but often felt unstable and acted a little wonky on- and off-road. Packaging a multilink suspension can be difficult, so you don’t always have the option of going with the exact system you want.
Control-arm length and position are also important factors. The short-arm versus long-arm suspension debate is always a hot topic in the Jeep world, and I stand by longer is better for most. If you have a Jeep Wrangler TJ (’97-’06) and it is lifted more than two inches, a long-arm upgrade is well worth investing in. Sure, you can make the stock-length arms work at taller heights, but the steep angle of the control arms tends to create terrible handling, a rough ride, and most four-inch and above short-arm lifts leave you little-to-no downtravel. The ’07-current Wrangler JK is fitted with much longer arms from the factory, which means you can get away with more lift and suspension travel without all of the negative handling effects experienced with the previous-generation TJ. Ultimately, I like long arms, and found that it’s one of the most worthwhile upgrades you can make.
Like Cappa, I am a big advocate for low-slung 4x4s. One of the biggest challenges with a low lift and big tire 4x4 can be controlling the suspension’s uptravel. Bumpstops are a relatively inexpensive way to prevent damage and keep your rig low. Yes, there are some expensive nitrogen-charged bumpstops, and if you are going fast off-road, they are worth the investment. For most trail wheelers, a basic poly or factory-style foam bumpstop can work well to keep your axle in check and tires from crumpling your body. The bumpstops will also save your shocks and springs in the long run.
If it’s a trail-only rig, the first suspension item to be removed completely is the front sway bar. You would be amazed at how much better your 4x4 will ride and perform off-road, just by disconnecting the sway-bar links. On a daily-driven rig, I suggest going with a set of sway bar disconnects, as the on-road benefits of a sway bar tend to be worth keeping it in place. If your vehicle happens to have a rear sway bar, I suggest leaving it on at all times. Rear sway bars tend to be more flexible and will actually add stability off-road without reducing travel significantly.
I grew up wheeling pickups, and found over the years that one of my favorite setups is a leaf-spring rear with links and coils or coilovers upfront. So long as you don’t go with an overly arched or soft spring, you can get ample performance out of a set of leaf springs and retain most of the payload capacity of the truck. On my old ’97 Ford Ranger project I went with stock Jeep Cherokee XJ coils upfront and Skyjacker leafs in the rear. The cost-effective setup on the Ranger project worked great and was very predictable off-road. Going with radius arms up front will make converting to a solid-axle on a mini-truck easier. When using radius arms, I like to limit the travel of the axle. Using limit straps will help to reduce the binding issues commonly faced with radius-style control arms and high articulation.