What does the colour code on the coil spring mean?

Most OE coil springs have a colour code. In many cases this colour code is a direct assignment to an original part number of the vehicle manufacturer. In this case, the colour code can be used to accurately select the spare part. However, it can also happen that the colour code is only a reference to a specific spring manufacturer. In this case, the color code does not refer to the original part number of the vehicle manufacturer. Then it is not possible to select the original part number using the colour code on the spring. More and more often the springs are listed in the spare parts catalogues of the vehicle manufacturers only by the colour code and not by the original part number. This makes sense because the mechanic of the authorised dealer who repairs a vehicle has access to both colour information. On the one hand on the defective spring, on the other hand in the original parts catalogue. This is the fastest and most accurate way to select a spring. For example, if the front axle spring with a red color marking of a vehicle is replaced, the mechanic simply orders two new front axle springs with the color marking “red”. The mechanic therefore no longer needs the engine, the equipment level, the suspension line, etc., the mechanic simply orders two new front axle springs with the colour mark “red” (selection criteria for a spring), as the vehicle manufacturer provides a simple and safe system for selecting and ordering the correct replacement spring. The colour marking is still clearly visible on the used spring even after years of use.

Why do cars with air conditioning or automatic transmission usually require different springs than vehicles without this equipment?

The air conditioning system or the automatic transmission increase the vehicle’s unladen weight.
So that the ride height of the vehicle after the exchange of the springs is identical with the one at the time of delivery, these vehicles must be equipped with stronger springs according to their higher weight.
Every carefully prepared catalogue of coil springs must take these criteria into account.

Why does it happen that the article numbers to be ordered for an axle of one vehicle are different?

This is particularly common with Opel or Toyota cars.
Since the vehicle manufacturer has designed the weight distribution on that certain axle differently, the springs on the left and right must absorb and balance different weights. This is why the springs are designed differently.
In order not to impair the driving characteristics of the vehicle, these subtle differences must be taken into account when replacing the springs.

Is there a risk of damage to the suspension when driving fast over bumpy roads?

Yes, unless the car or chassis is specially designed for off-road use.
Under extreme conditions, springs can break relatively quickly. Such a load also means increased wear for shock absorbers.

Why should suspension springs always be replaced in pairs?

Even if only one spring of the wheel suspension is broken, the springs on both sides have been exposed to the permanent stress of vehicle weight and external influences (salt, stone impact, extreme cold…). The unbroken spring is often already compressed by a few centimetres due to the permanent stress. The different spring strengths of new and worn springs would cause the vehicle to be misaligned when replaced individually.
At best, this can cause a claim. If the vehicle misalignment is not detected, unstable driving behaviour and an increased risk of over- or understeering during braking are to be accepted.

May the replacement spring differ from the old, dismantled spring in geometry or wire diameter?

No, because the physical properties change with every deviation. All SUPLEX springs have been manufactured exactly according to the original specifications and therefore comply with the current OE standard. No changes are made for economic reasons, which make the springs appear cheaper in production.
Any change in design or wire diameter is a clear intervention in the design of the suspension and can extremely impair the driving characteristics of the vehicle.
Any replacement spring that does not correspond to the original design therefore represents a danger.

Is one type of suspension preferable to all others?

Not in everyday use. This is because every type of suspension is a compromise between comfort and safe road traction. In addition, some things about the suspension are a matter of taste. While vehicles of French and US American origin usually have a softer suspension, German vehicles are designed comparatively tough. A harder suspension causes a better grip, a soft suspension is more comfortable. Hard springs also absorb lateral forces (curve inclination) better, but have poorer road contact on bumpy roads.

Can I damage my suspension by overloading?

Yes, every car has a maximum permissible total weight. You can find out how high this is in your operating manual and in the vehicle registration documents. Apart from the fact that the driving characteristics of an overloaded vehicle have a negative effect: Excessive loading of the springs can lead to breakage.

Why are leaf springs no longer used in the suspension of the front axle?

First and foremost because leaf springs do not provide the necessary stability and are too large. Coil springs are also cheaper to produce. In addition, leaf springs require regular maintenance.

The newly delivered reinforced coil spring is shorter than the old original spring from the vehicle. Will this shorter spring change the vehicle height?

No. The main characteristic of a reinforced spring is its thicker steel to increase the spring rate. Doubling the wire diameter results in a 16 times higher spring rate. If the new spring had the same length as the removed one, the higher spring rate would change the vehicle height upwards. Since this is not desired, the new reinforced spring is shortened by the corresponding factor so that the vehicle height is correct.

How do I recognize a good quality aftermarket spring?

The easiest way for the mechanic to check the quality of the aftermarket spring is a direct comparison with the OE spring on the vehicle. An OEM spring is usually easy to identify. They usually have a color or letter code. Even if the aftermarket spring does not have this code, the spring shape and geometry should be the same.
Not all coil spring manufacturers have the ability to offer this OE technology.
An aftermarket constant wire coil spring has a different dynamic ride than a conical wire spring.