Types of retarder
There are three main retarder technologies for tractorheads, each with specific advantages depending on the type of operation:
- Hydrodynamic retarder (Voith, ZF): Uses pressurised oil inside a chamber with rotating vanes to create resistance against driveline rotation. The Voith VR 115 and VR 120 are the most commonly fitted models in Europe. Delivers braking power up to 500 kW (680 HP) and is particularly effective at high motorway speeds. Its main advantage is constant braking power independent of engine speed.
- Intarder (ZF, Mercedes): Hydrodynamic retarder integrated directly into the automated gearbox. The ZF Intarder is available in TraXon gearboxes (DAF, MAN, Iveco) and the Mercedes Intarder in PowerShift units. Integration reduces weight and space compared to an independent retarder. Braking power up to 600 kW on the latest models.
- Decompression engine brake (Jake Brake): Not a retarder per se, but a braking system that opens exhaust valves during the compression stroke to turn the engine into a compressor that slows the vehicle. The Volvo VEB+ reaches 375 kW, MAN EVBec 400 kW and Scania Retarder (electronic) 500 kW. Its advantage is adding no weight to the vehicle.
Why the retarder matters
On a typical mountain crossing such as the Brenner Pass (Austria-Italy) or the Somport tunnel route (Spain-France), a 40-tonne truck may face 20-30 km of continuous descent. Without a retarder, service brakes overheat (brake fade), losing effectiveness and compromising safety. With a retarder, 80-90% of braking is performed by the auxiliary system, keeping service brakes cool and available for emergencies. Additionally, brake pads can last 400,000-500,000 km instead of 150,000-200,000 km, representing significant maintenance savings.
Retarder by brand
Each manufacturer offers differentiated retarder solutions:
- Volvo: VEB+ (Volvo Engine Brake Plus) standard on many FH configurations. 375 kW engine brake combinable with optional Voith retarder.
- Scania: Own integrated retarder up to 500 kW, considered the best on the market for its progressiveness and quietness. Available as standard on most R and S configurations.
- Mercedes: Intarder integrated into PowerShift 3 gearbox with up to 600 kW. The Actros also offers the 475 kW High Performance Engine Brake.
- DAF: ZF Intarder integrated into TraXon or independent Voith retarder. The MX Engine Brake delivers 360 kW.
- MAN: EVBec (Extra Valve Brake with compression release) at 400 kW integrated into the D26 engine. Combinable with Voith VR 115.
- Renault: Optibrake+ (320 kW engine brake) as standard. Optional Voith retarder across the T range.
- Iveco: ZF Intarder in the HI-TRONIX gearbox. Iveco Turbo Brake engine brake at 400 kW.
