Mike Stevens | Aug 7, 2008

Prepared to be Shocked!

If you, like me, have friends who enjoy tinkering with cars and working out how to get the most out of them, then the conversation at some stage would have turned to upgraded suspension components. High on the list of topics being shock absorbers.

So what benefit comes from an upgraded shock absorber? First, it’s important to understand what a shock absorber does. Ride, handling, steering-control and braking and are all controlled to a degree by the shock absorbers. So, on that score, upgrading your shock absorbers would mean an overall upgrade in key areas of any car’s handling characteristics.

Hopefully, by now this has grabbed your interest. It’s understandable why drivers would want a more compliant ride, better or ‘crisper’ handling (giving the driver more communication as to what the car is doing) and stronger, more predictable braking. Overall, just more control of the vehicle you are pedaling.

It is the shockers that keep your tyres in contact with the road – without shockers, the wheels would bounce like basketballs making the car completely uncontrollable.

So let’s look at the most common types of shock absorber to ascertain the differences in design.

Monotube

bilstein04Since Bilsteins’ inception over 40 years ago, Bilstein has been a unique driving force in the automotive suspension industry. Bilstein was first to apply the patented gas pressure principle to controlling ride characteristics on vehicles, and introduced the world's first ‘monotube’ gas pressure shock absorber.

The ‘Bilstein principle’ (its core philosophy) is to manufacture the strut/insert with the rod pointing down (inverted) into the strut tube, thereby utilizing the thicker, stouter body portion of the shock absorber to dissipate side loads.

In short, due to the increased diameter and surface of the pressure tube, the Bilstein Gas Pressure Strut/Insert is better suited to take increased side-loads when compared with the conventional twin-tube strut/insert. Many suspension manufacturers have since ‘borrowed’ this leading design and philosophy and have adapted it to their own products. But having so many slightly different variations of design, I’ll stick just to one manufacturer, Bilstein, so things don’t get to confusing (or for this article to become a novel).

The Bilstein Gas Pressure Strut/Insert, whose development was strongly influenced by the motorsport industry, has other advantages besides rigidity and strength. It also provides greater stability, better road handling and accurate steering.

Twin Tube

The conventional McPherson strut (is based on the use of the twin-tube shock absorber): the piston rod protrudes above the McPherson strut assembly and attaches to the sprung mass of the vehicle. This differs from the mono-tube where the piston rod is completely encased and protected from contamination - the mono-tube also has less moving parts. In the case of the twin-tube application, the piston rod has to absorb not only compression and rebound forces but tremendous side loads. Basically, there are more forces at play during the harsh life a twin-tube shock absorber. Oh, if only shocks could talk!

So it seems the mono tube design is better because of its higher piston rigidity, longevity, serviceability and improved lateral load performance and heat dissipation.

koniworkings1

This last point, heat dissipation, is the next topic that we will look at.

Heat

Heat is one of the major detriments to the performance and longevity of any shock absorber. Conventional twin-tube shocks trap the heat within the shock body which, in turn, prevents adequate heat dissipation making them more prone to heat buildup, fade and eventual failure.

Although it’s a lot harder to feel ‘shock fade’ compared to something more tangible like brake fade, it does still happen.

When the piston rod moves, oil is forced through the valving to convert kinetic energy to heat. As the piston moves in, the gas will compress and vice versa.

Bilsteins patented monotube gas-charged design allows the excessive heat from the oil to transfer to the outer surface of the shock body and dissipate more efficiently. The dividing piston also permits the oil to expand as heat builds, preventing aeration (foaming) and viscosity loss. This allows the shock to maintain full damping characteristics as temperatures rise.

Anything else?

The ‘rising rate’ valving of the Bilstein shock absorber provides the necessary damping to react quicker to road conditions without sacrificing ride comfort. This combination of valving and high pressure nitrogen gas keeps the wheels and tyres in constant contact with the road helping to ensure safety through enhanced control.

But the shock absorbers are only one part of the equation. Springs are the other essential ingredient in getting the best out of your car, but that’s another story.

Till next time, happy and safe motoring.

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