Brake pads in OE quality: What Knorr-Bremse does differently

The brake is what decides what the free Lorry workshop can seriously promise the fleet customer. Braking distance, noise behaviour, service life of disc and pad, consumption, particulate matter: all this depends on whether the pad, disc, caliper and axle are matched to each other as a system. If you install a less expensive pad whose friction coefficient curve or heat input deviates from the design, this shifts the behaviour of the brake. This sometimes happens visibly, often only over weeks and months.

Knorr-Bremse - as co-founder of Alltrucks in a joint venture with Bosch - develops brake linings in OE quality for precisely this logic. A pad fits the brake because it was developed according to the specifications with which the brake is approved at the factory. This article first explains what is behind the term. It also shows which tests go beyond the European minimum standards. Finally, it clarifies why NVH tests, residual grinding torque and friction mass optimisation are more than just technical catalogue lyricism for the independent commercial vehicle workshop.

OE - Original Equipment - does not describe the sticker, but the development and release path. A pad in OE quality is developed against the specifications with which the brake is approved for series production. These include friction coefficient curve over temperature, noise behaviour, wear behaviour, heat input into the disc and bearing as well as compatibility with the caliper. These specifications are not public, but are the property of the brake manufacturer. At Knorr-Bremse, they therefore flow directly into the development of the pads for the aftermarket.

ECE R90 is the European minimum standard for brake pads. It defines the minimum requirements, not the optimum. Knorr-Bremse therefore tests its brake pads in three additional dimensions: vibration, wear and performance. In particular, this includes the noise-vibration-harshness test, which evaluates the acoustic behaviour and vibrations across the entire braking system.

The crucial point: With OE quality, it is not the pad that is tested in isolation, but the system. The manufacturer looks at the pad, disc, caliper and axle together. It is precisely this view that gives a pad its stable, predictable behaviour in the field. This is why it ultimately makes the difference in the independent workshop between a job that is completed cleanly and one that comes back three weeks later with a squeaking noise or uneven wear.

NVH stands for Noise, Vibration, Harshness - Noise, vibration and sensation of harshness. The NVH test evaluates the acoustic and vibration impact of a brake pad in combination with the brake disc, caliper and axle. High-frequency squealing noises, low-frequency humming sounds and vibration excitations that are transmitted into the cab via the chassis are also tested. This is therefore relevant for the driver's comfort and therefore also for the complaint rate in the workshop.

Standard vibration and wear tests cover a large part of the flooring behaviour, but not all of it. The NVH test, on the other hand, closes a gap that often leads to complaints in practice: the noise behaviour under realistic load cases, in different temperature and humidity ranges. Knorr-Bremse therefore uses the NVH test as a supplement to rule out noise anomalies even before series production is released. This means that the problem is not only noticed when the workshop receives the complaint on the phone.

Even if the driver takes his foot off the brake pedal, there is still minimal contact between the pad and the disc - the Residual grinding torque. Es lässt sich nie vollständig auf null bringen, aber konstruktiv minimieren. Hohe Restschleifmomente erzeugen Wärme in der Scheibe, beschleunigen den Verschleiß an Belag und Scheibe und belasten zudem das Radlager. Über die Lebensdauer eines Lkw summieren sich diese Effekte daher zu einem messbaren Mehrverbrauch und kürzeren Service life.

Knorr-Bremse brake pads, on the other hand, are matched to the entire brake system and grind less on the disc compared to alternative qualities. This has two consequences that are directly visible in the workshop. Firstly, the brake disc and therefore the wheel bearing are heated up less. In addition, the pad itself lasts longer.

Knorr-Bremse also offers brake pads with APR system on. A spring system actively disengages the pad and disc from each other after each braking application, i.e. decouples them. The effects are therefore visible in practice:

The Friction material - i.e. the mixture of friction material, binders and functional additives - is the core of every brake pad. It defines the friction coefficient curve via temperature, wear behaviour, noise susceptibility and also the heat input into the disc. At Knorr-Bremse, the friction material is therefore optimised for three simultaneous goals: maximum performance, minimised wear via the lowest residual grinding torque and reduced heat input, which protects the wheel bearing.

Diese drei Ziele stehen normalerweise im Konflikt. Mehr Leistung bedeutet typischerweise mehr Wärme. Mehr Verschleiß bedeutet längere Service life, aber auf Kosten der Leistung. Die Auslegung über das gesamte Bremssystem statt am isolierten Belag ist dagegen der Hebel, der diesen Konflikt entschärft. Genau das ist somit der Unterschied zwischen einem Belag, der die ECE-R90-Mindestnorm erfüllt, und einem Belag in OE-Qualität.

The technical level is one aspect. The other is the workshop-side consequence: what does OE quality mean for the inspection, the Lead time and the complaint rate?

OE-quality brake pads behave in the field in the same way as the vehicle manufacturer intended for series production. This means fewer surprises at the next inspection. The pad thickness is within the expected range, the disc shows the expected scoring and wear characteristics and the noise behaviour is also inconspicuous.

Squealing brakes, uneven pad wear, premature disc wear: these are the typical reasons for complaints after a pad change. If, on the other hand, you work with a pad that is NVH-tested and whose friction mass is matched to the disc, you have fewer calls and fewer goodwill appointments. In a workshop with a shortage of labour, this is Multi-brand capacity a direct economic effect.

A fleet planner who calculates the total cost of ownership does not ask for the list price of the disc. Instead, he asks about service life, consumption and follow-up costs for the disc and bearing. Original equipment quality is therefore the argument that carries weight in every order discussion.