Suspension & Shock Absorber Test


The easiest shock absorber tester of all:

  1. -Start and drive

  2. -Brake when prompted (approx. at 5 km/h)

  3. -Wait few seconds and look at the results


What is pitch and how it is measured?

It is a common experience: when you apply brakes, your the front of your car pitches. This happens because the car body is connected to wheels by means of the suspension springs;  although this reduces the intensity of mechanical vibrations due to road imperfections, it also requires that oscillations are damped as quickly as possible, in order to avoid uncontrolled pitching which may affect stability.

Springs and shock absorbers are designed to ensure both good stability and ride comfort. Since they affect safety, in many countries they have to be periodically checked. We won’t go through the complex legislation, test methods and evaluation criteria, because very expensive equipment is involved. Instead, we’ll focus on the simplest test method, which consists in loading the front of your car with your full weight, and suddenly unloading it: this procedure was largely used in the past; of course, evaluation is subjective, and the operator usually checks that the damping action of the shock absorbers is “good enough”.

Now, iSuspend mimics this procedure, offering some numerical data (which was missing in the “manual procedure” described above). But there’s another important factor: cars are everyday larger and heavier, and making an SUV pitch with just the power of your arms is not easy at all!

Here’s how iSuspend works: it asks you to accelerate to a very low speed (few km/h are enough), the prompts you to brake. Yes, apply full brakes (gently, avoinding any slip) until the car comes to a complete stops: this makes the front pitch! From now on iSuspend records oscillations for 2 seconds, and displays the results.

Test path smoothness and horizontality are essential! Also, the iPhone shall be firmly attached to the car body, in as low a position as possible, e.g. on the cabin’s floor, passenger side; some adhesiv tape may help. REMEBER: any movement of your iPhone with respect to the car’s body affects the results!

Evaluating the results

It is not easy to say when a shock absorber works properly or not. For this reason we don’t provide any absolute criteria, which largely depend on the manufacturer and on the car model. However, we provide MAXIMUM and MINIMUM PITCH, and show a graph.

A typical passenger car shall exhibit a maximum pitch of not more then 10°, which should be damped quickly. Ideally, no oscillations should be visible, apart from the first one. Here you are two examples: the left one shows un underdamped behaviour, although absolute oscillation values are within reasonable limits; the right one is the typical behaviour of a good suspension:

                        BAD                                           GOOD