The Performance Shocks Guide
As shocking as it may sound, shock absorbers are probably one of the most useful inventions of the automotive age. Imagine if you will a world without shock absorbers. The tiniest bump or dip in the streets would send violent, shimmying waves pulsating through your vehicle without end. Any off-pavement trek would have to be followed by an immediate trip to the dentist for emergency replacement of the fillings and crowns that were jarred out of your molars.
Thankfully, this twilight zone scenario exists only in our darkest nightmares, and shock absorbers have been invented and do take the shake, rattle and roll out of our vehicles. These slender cylinders are the unsung heroes of your suspension system, and it's time to pay tribute by learning a little bit about what makes them tick.
The outside of a shock is hardly interesting, but its guts are where the magic happens. Let's pull out a cutting torch, dissect a standard shock absorber and see just how these marvels work:
- Mounts:
- A shock serves no purpose unless it's mounted firmly to your chassis. Depending on the suspension type, the mounts will be either eye style (donut shaped) or stem style (hi-hat shaped). The mounts are lined with a padded cushioning, usually rubber or polyurethane.
- Cylinder:
- Home sweet home. The cylinder is the tough outer housing for the shock's intricate inner workings. The size of the cylinder is one of the most important factors in the overall performance of the shock. A larger cylinder means a bigger piston and more oil, and when it comes to shock absorption, bigger is better. For corrosion resistance and eye-catching looks, the cylinders are usually painted with enamel or finished with a rust-repelling coating like nickel or chrome.
- Boot:
- A shock is made for absorbing, and that's just what it will do with a protective boot. This durable cover blocks dirt, grit and road crud from making its way into the shock and gumming up the works. Shocks are tough, but their innards are still susceptible to wear and tear. The boot provides a shield against mud clods, and it enhances the style.
- Piston Rod:
- One of the main components in a shock, the piston rod is the backbone. The oscillating energy of the springs transfers directly into the piston rod, which then plunges the piston into the oil to dampen the bounce. Often, the piston rod is hidden under the boot, but it's always at work when the vehicle is in motion.
- Piston:
- As you would expect, the piston is mounted at the end of the piston rod. As the rod throbs up and down from the spring's energy, the piston rams into the oil, creating the hydraulic pressure that smoothes out your ride. The diameter of the piston matches the diameter of the cylinder (or the cylinder's inner chamber where the main oil supply is). This design maximizes the pressure strength because the oil cannot flow around the piston, only through the valve.
- Valve:
- The valve is a conduit that controls the flow of oil from one area of the shock into another. When the piston pushes down into the shock, the oil moves through the valve. Only a small amount of fluid can pass through the valve at a time, and this creates the hydraulic pressure that dampens the spring's energy. Most modern shocks have road-responsive valves. When the street is calm, the valves open up for a softer ride. But, when things start to get hairy, the valve closes off for extra stiffness.
- Oil:
- Forget about canola oil—shock are filled with nothing less than industrial grade goo. Of course, the oil has to be rugged because it's the final step in the dampening process. The kinetic energy from the bouncing spring transfers to the piston rod, which sends the piston plunging into the oil. The highly viscous oil resists the piston's motion and absorbs the kinetic energy, which transforms into heat.
A shock absorber is an incredibly simple and effective part of any suspension, and it has only one shortcoming: high temperatures. All the energy created by the springs has to go somewhere, and it ends up morphing into heat. Unfortunately, when the oil's mercury starts to rise, its viscosity starts to thin out and absorbs less energy. If the oil gets too hot, it can start to bubble like a pot of boiling water, causing a dreaded case of shock fade.
Besides just dampening, a good shock must also be engineered to dissipate heat efficiently for consistent performance. The primary way to keep fade and foam in check is through maintaining high internal pressure. Ever wonder why a radiator doesn't boil over unless you open the cap? It's because your coolant is pressurized, and pressure greatly increases a fluid's boiling point. Shock absorbers work the same way. In general, shock fade is kept at bay through gas charges and tube design. Let's investigate the 3 most common designs:
The twin-tube shock can trace its lineage back to the mid 20th century, and its ingenious design still stands the test of time. As its name implies, twin-tube shocks have 2 chambers: an inner and an outer tube. The inner tube is where most of the work takes place. Here, the piston plows up and down through the main supply of oil. The outer chamber holds an extra supply of oil and a low pressure gas charge at around 100–150 psi. The gas, usually nitrogen, provides the backstop against the flow of oil for mega dampening. However, as the oil heats up, it can mix with the gas and cause foam and fade.
Twin-tube shocks deliver comfortable, stable all-around dampening for cars, trucks and SUVs. In fact, twin-tubes are probably the most commonly used shocks in the automotive market today. Ideal for street driving, they feel smooth yet still reduce body roll and sway during cornering and dipping during hard stops and spirited acceleration. However, rugged off-roading can cause the twin-tubes to overheat, which leads to foam and fade in extreme conditions.
Foam cell shocks are nearly identical in design to twin-tubes. The key difference is that the gas is trapped inside of tiny little capsules rather than free-floating. By separating the gas charge from the oil, the risk of foaming is nearly eliminated while still providing the comfortable ride quality of a twin-tube shock. However, foam cell shocks are vulnerable to overheating. If the oil in these shocks gets too hot, the foam cells can erupt. After that, no matter how long they cool down, they'll never regain the same level of performance.
One may be the loneliest number, but monotube shocks have no problem leading a solitary life. Rather than using two chambers, these burly shock absorbers do it all in a single tube. What's more, they have twice the piston power as a twin-tube shock. The first piston is located right where you would expect it–at the end of the piston rod. This first piston pushes against a section of oil, which is forced downward into the second piston. This floating piston is sandwiched between a section of viscose oil and a pocket of highly charged gas (between 200–360 psi). By separating the oil from the gas, monotube shocks greatly reduce the risk of oil foaming and fade.
The dual piston design of monotube shocks provides stiffer dampening, which is preferred for sportier handling and grueling off-road conditions. Monotube shocks are also air cooled, so they do not retain heat the way twin-tubes do. Plus, they can be mounted upside down for extra weight support. However, monotube shocks are difficult to mount in place of stock twin-tube shocks on cars and stock-height trucks and SUVs because of the added length and range. Also, monotube shocks are slightly more vulnerable to dent damage because there is no outer buffer.
It's hard enough to go into a grocery store and find the perfect tomato—choosing the right shock absorbers for your vehicle shouldn't leave you pulling your hair out with indecision. The selection is large, so use these questions to narrow your search and find the perfect set of dampeners:
Different terrains call for different degrees of dampening. What works on a fresh stretch of pavement is murder on the washboard "driveway" leading to your distant relative's rustic hovel. Here are some tips for selecting the best set of shocks for your driving habits:
- For standard street cruising, go with a set of multi-stage valving shocks. They automatically respond to varying road conditions, staying cushiony on smooth routes and getting stiffer when you roll into pothole country. Edelbrock Performer IAS Shocks represent this shock style.
- For the occasional off-roader, a beefier set of shock absorbers is key. A thicker cylinder, a larger piston and dust boots are highly recommended. Shocks similar to Skyjacker Nitro 8000 Shocks are up to the task.
- For wild and wooly off-road adventurers, only the toughest, stiffest, most durable shock absorbers will do. Monster-size monotube shocks deliver superior dampening for heavyweight rigs, and mammoth coilover shocks offer unmatched performance both on the Rubicon or on Route 66. You probably want to get a set of shocks with an oil reservoir for enhanced heat control and less fade, similar to Fabtech Dirt Logic Shocks.
Having the right type of shocks is important, but not as important as having the right number of them. Here are some suggestions:
- For drivers who always keep all 4 tires on the pavement, the rule of thumb is 2 shocks per axle. 1 at each wheel should be enough to handle even the most dilapidated stretches of road.
- Vehicles with heavyweight bumpers, snow plows or winches should consider upgrading to a multi-shock kit. Adding a few extra dampeners to your front-end counters the instability of the excess pounds.
- For lifted vehicles with larger tires, multi-shock kits are also strongly recommended. They reduce body roll while cornering and provide much needed stability on rocky trails. Plus, they add an imposing look to your front wheel wells.
Like most aftermarket accessories, shock absorbers come in a wide range of finishes. Besides enhancing your vehicle's image, these coatings and treatments block out corrosion. Here are some suggestions:
- For a more traditional look, get a set of shock absorbers with a white enamel finish. This classic coating has been around for generations, and it still remains quite popular. Plus, the enamel puts up an effective barrier against rust and oxidation, as long as it does not get scratched. Rancho RS5000 Shocks have the classic look.
- When you want a more eye-catching appearance, get metal-plated shock absorbers. From glimmering nickel to sparkling chrome, these metallic shock absorbers have a tough look and the rust-resilience to back it up. Edelbrock Xtreme IAS Shocks are a great pick for this finish.
We hope you have found our Suspension Kits Research Guide Center a good guide in helping you choose the best Suspension Kits for your vehicle. It is AutoAnything's goal to provide the most information on the Internet and through our Auto Accessory Specialists on every product we sell. If you have any information that you think could help improve this section, please email us at researchcenter@autoanything.com.