Suspension isn’t complicated - some springs to hold up the car and take the bumps and some shock absorbers to keep the motion in check. Of course, if it were that simple there wouldn’t be huge industries built up around it and you probably wouldn’t be reading this. I will admit, however, that I didn’t know just what went into to designing and supporting an overland suspension system until I had a chat with one of the giants in the space, ICON Vehicle Dynamics.
I’ve had ICON’s VS 2.0 smooth body shocks, their entry level shock, on my daily driver/adventure rig, a 1997 Land Cruiser 80, for about 3 years and 36,000 miles. They’ve been a great addition, adding incredible body control on and off-road.
Recently I decided it was time to have my shocks rebuilt. A perk of this design is they are fully serviceable, including shock valving. This article is therefore going to be part services and part technology as we track my rebuild and talk with their lead engineer.
Let’s begin with the basics - a spring, as mentioned above, is the component of the suspension that supports a load while also absorbing an impact. Springs however aren’t enough as they simply store kinetic energy and redistribute it in a decaying wave pattern. Without a way to take some of that energy and dissipate it, a car really isn’t drivable.
Here, let me show me you.
A damper takes that kinetic energy and converts it into heat energy. At its core, a damper is a fluid filled body with an attachment point on one end. Inside the tube there is a piston attached to a shaft with an attachment point at the other end.
How the fluid and the piston interact is where the conversion magic happens. The piston resists the motion of the shaft relative to the body as it tried to force its way through the fluid cavity, converting the kinetic input energy into heat. That energy heat is absorbed by the fluid and then radiated away at the body to the atmosphere.
Heat kills shocks.
Excessive heat breaks down the fluid, puts pressure on the seals and actually attacks and breaks down the seals leading to early or sudden failure. Making a durable shock means managing heat. The VS 2.0 is so named for its body diameter of 2.0 inches, or a little over 50 mm. Body diameter is directly related to internal volume, more volume means more fluid to absorb heat.
The equation for the volume of a cylinder, if you remember middle school math, is πr2L. You can’t change the length the shock body easily, as you are physically constrained by the suspension design. Good news is that diameter is the one you want to change anyway, since the diameter, or rather the radius, is squared in the equation.
While doubling the length results in twice the volume, doubling the radius quadruples the volume. More fluid volume is an automatic win for keeping heat at bay, which is why ICON’s smallest shock is still bigger than many aftermarket shocks for the same applications and much bigger than stock. Stock or other popular off-road shocks range anywhere from 30 – 46 mm. On top of that, ICON uses aluminum bodies instead of steel. Aluminum is a great heat radiator as well as having other desirable shock properties, but it’s more difficult and expensive to manufacture.
For even greater volume, move up to 2.5 or 3 inches depending on application. Moving from a 2 to 2.5 inch shock gives you roughly 65% more fluid capacity and nearly 80% more shock body area to shed heat. Adding an external reservoir increases that even more. If your shocks start to feel loose after a long hot day on washboard road, you may need additional fluid capacity to combat this fade.
So how hot is too hot? I talked to Dylan Evans, ICONS lead R&D engineer about the technology.
“About 450F is where things start breakdown and seals start to harden, you can spend a little time in that range, but not a lot.”
450F! That’s hot and if you have any doubts, go drive a rough road and feel your shocks…actually don’t do that I don’t want to be responsible for burns. The fluid can take that kind of heat partly because it’s a high-quality synthetic, and partly because ICON uses another trick - pressurizing the fluid with nitrogen, an inert gas.
Boyle's law says pressure and temperature are related; raising the pressure of a fluid raises the boiling point that fluid, which is also why your engine cooling system is pressurized, BTW. You don’t want your coolant or your shocks to boil for much the same reason, once it does you form air bubbles which cause no end of problems. In the case of the shock these bubbles form voids where the piston isn’t acting on a fluid, reducing its effectiveness. This is called shock fade and it feels like a shock that isn’t doing its job.
Fade = bad.
Moving to the 2.5 or larger shock also moved up the feature chain and nets you internal compression zones and optional external adjustability.
Compression zones are like little mini shocks inside the shock for the very bottom or top of the cycle. In these narrowly defined zones, the damping rate is up to 100% higher, rapidly slowing down the piston, preventing harsh bottom out and top out events. This lets you run a more relaxed main valving and spring configuration for better control and comfort.
I’ve always felt my shocks were a little on the firm side for me in compression damping, or how much the shock resist compression, and that’s the main reason I am doing the rebuild. My truck, unlike so many 80 series, is pretty much stock weight having no real weight adders like bumpers, winches, etc. I’ve always assumed that my ride was a result of the shock being generally setup for a heavier vehicle than mine as the ride improved with weight. I was right, but in the wrong way.
One of the things that impressed me immediately in chatting with Dylan was that ICON isn’t interested in churning out generic products for anyone and everyone, but rather focused on doing a smaller number of products better.
In our conversation he told me about his personal 80 series that use used for the development of the 80 series components. For promotional purposes, it not only had the development lift kit but it had all the usual goodies – bumpers, winch, lights, etc – adding to the weight. Go to the site and you can see it in its former glory. Former because Dylan tells me not long after those pictures, it found itself wrapped around a tree by another shop outside of his care. Pour one out for a great looking 80. Pour one out for a beautiful 80 taken before its time.
First off, yes, the kits are individually tuned for every model. Every single vehicle ICON makes a shock or kit for is tested to be optimal for that exact model. Is it any wonder I can only reach him by phone on his way home from testing more suspension in the desert? It’s a wonder he has time for anything else.
Back to the point, Dylan tells me that adding this kind of weight is so common on the 80 that they built the kits around an additional 400 lbs static weight. I also can’t fault them for this assumption of weight, as you rarely find featherweight, let alone stock weight 80 series these days. This explains my harshness unladen completely and illustrates why a one size approach simply can’t work with suspension. Note: They only make this assumption for 2 vehicles currently.
Icon doesn’t require that you send them back to them for service and there are approved shops in most parts of the country. They don’t even mind you rebuilding them yourself and while I was tempted, having been a mountain bike suspension tech many years ago, I figured who knows how to do it right better than they do?
One thing I worried about was whether they would be able to understand my best description of what I needed and not make too subtle of changes or in too far the other direction. I needn’t have worried, with all the testing they do, you can bet what you are feeling, is something they’ve felt, and they acutely understand. Plain English, and not some technical jargon seems to have been translated perfectly.
This is one of the key benefits of a company like this, you aren’t only buying a quality product, you are buying dozens of years and hundreds of thousands of miles of experience and expertise. This is an engineering company, and it shows.
During my rebuild process, they replace all the seals, the oil, replace 2 scratched shafts, and all rubber bushings in addition to changing the valving. The basic $75/shock fee covers the new valving, seals and oil.
Full disclosure, I paid for this service out of pocket and have been given nothing in terms of compensation for writing this story though they were kind enough to take pictures of my shock service for this story for which I am very appreciative.
I am very impressed with what I got back and I’ve had several people ask if they were brand new. The only downside was that my turnaround times were longer than I had hoped for and a clear picture of my service order and its status was difficult to get through the service channels. Not a deal-breaker, but it was a little frustrating and did cause me to change up some plans because of the delay. To be fair, part of that was supply chain issues that are affecting everyone right now.
I’ve had my shocks installed for about a week now. The excellent digressive rebound characteristics that I loved for body control are still there but the edge on the compression is substantially smoothed out without losing on road feel or bottom out performance. In short, they nailed it, it’s exactly what I asked for.
Which brings me to one of the more interesting things I learned about ICON. Don’t think of them as a shock company, but rather a solutions company. I know that sounds like 2020’s cooperate nonsense, but it means is they see the suspension system holistically, not in parts.
Dylan describes the process as 80/20. 80% is the easy part – the technology is mostly common among all the top brands and there isn’t a lot there to differentiate one from another. This part is just getting the list checked off and the thing built. he 20% to get it just right is where the hard work is.
“We didn’t take the easy route.” He tells me confidently.
“We design the shock [dimensions] first, getting the physical limits of the suspension cycle, then we design the springs and other parts needed to get that cycle.”
If the goal is simply to be taller in order to fit taller tires, any old lift will do. With some kits, the suspension travel is traded away for lift heigh, compromising ride, balance, articulation and durability. Just put a taller or stronger spring in it and boom, lift kit.
The problem is now you are topping out most of the time, and in coil bind the rest of the time or with a horrible static ride height ride and no suspension articulation or balance. Another issue not addressed by lesser kits are pressure points on hardware leading to potential failure. An example would be the upper control arm in a double wishbone front IFS, which places limits on suspension cycling and when lifted presents unacceptable angles for the ball joint, leading to premature failure and worse suspension range.
Instead, ICON starts with maximum travel range, where its limited and then designs, builds, and tests its own components around that. Having sufficient up travel means better ride and control when the suspension unloads suddenly like driving over a rise or after a bump and having sufficient down travel means going deeper into a spring and damper allowing for more energy to be redirected and converted by springs and shocks.
Having a good balance between the two means a lighter spring rate and damping curves for better ride without compromising at the limit performance. Maximizing the cycle also allows for the most wheel articulation for more traction, more stability and more comfort in tackling low speed work. What good are bigger tires if you are lifting them off the ground more often?
Does all this cost money? You bet! And ICON aren’t exactly the budget option. That being said, I have their completely affordable entry level shock with someone else’s springs and they perform better than any other options I’ve tried to date in this price range. The other factor to consider is that these shocks, barring massive damage, are rebuildable for an indefinite service life.
Speaking of which, ICON does indeed engineer its own springs and matches their spring rates and curves for ideal performance for a given application.
Generally, there are 3 types of spring rates. Linear, progressive and dual rate.
Linear are just what it sounds like, a constant spring rate from the top of the coil or leaf to the bottom.
Progressive are springs that progressively apply more rate at different parts of their cycle. This sound ideal; a soft ride with strong bottom out performance, but Dylan tells me they are often too narrowly tuned to offer real benefits.
Lastly is dual rate, which is what I have on the Cruiser and what is included in the rear of the kit for my cruiser. A dual rate is a spring that is soft in one section and firm in the rest. A typical overload spring pack on a pickup is dual rate. With coils, the soft rate is nearly in bind most of the time and the majority of the work is done by the harder coil.
The additive effect of the rates is someplace between the firm and soft rates but you have the benefit of a compliant initial rate and better down travel. As the axle swings down the soft coil unloads and as its been mostly in bind it has a lot of expansion, keeping the coil in the spring perch and applying ground pressure to the wheels as its helping push the axle to the max of its down cycle. With linear rate, the spring length needed for a similar length would be impractical and go into coil bind before max up travel.
Choosing the right coil for the right application is far more than just picking the “ideal” type and looks holistically at the damper, the cycle and the design. For example a linear coil is better for the front axle where a dual rate might be ideal for the rear.
I was tempted to get their springs, but it adds 3 inches heavy and I would get 3.5 inches light and with that… I wouldn’t even fit in my garage! I guess next is a taller garage.
There are obviously other great solutions for suspension systems, budget, midrange to premium that cater to the daily driver, weekend warrior or expedition outfit. This hopefully give you an idea of what to look for when you are picking your next system. My advice is to find a company that does more than add springs and shocks for total performance.
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