Tie rod

Track rods transmit steering forces and help determine the toe alignment of the steered wheels. On rigid steered axles, they generally connect the left and right steering arms; in rack-and-pinion steering systems, individual track rods connect the steering rack to the steering knuckles. Play, deformation or incorrect adjustment causes imprecise steering and accelerated tyre wear. Correct replacement therefore requires both identification of the axle specification and a check of the complete steering geometry.

Always identify parts using the vehicle's chassis number, supplemented by axle identification and original part numbers. Visual comparison or selection based solely on the model name is never sufficient. Within the MAN TGL, TGS and TGX or Mercedes Atego, Actros and Arocs ranges, track rods vary according to axle load, track width and the position of the steered axle. MAN Lion’s City and Mercedes Citaro also use axle-specific versions. On Neoplan buses and Mercedes Tourismo, Travego, Intouro and Conecto, the axle specification likewise determines the choice of track rod. MAN TGE and Mercedes Sprinter use track rods for rack-and-pinion steering. The engine variant is not a standalone selection criterion: the steering and axle configuration fitted to the vehicle remains decisive.

Distinguish between complete cross-link assemblies with track rod ends, rods with separately replaceable ball joints, and axial joints with outer track rod ends. Check the centre-to-centre distance, tube diameter, wall thickness, bend, thread diameter, pitch and whether the thread is left- or right-handed. Taper dimensions, taper angle, installation orientation and articulation range must also match. Steel tubes or solid rods, hardened steel ball studs and elastomer dust boots are designed to withstand varying tensile, compressive and bending loads. A similar length therefore does not guarantee correct fitment or load capacity.

Typical symptoms include knocking when changing steering direction, wandering on straight roads and sawtooth wear on the tyre tread. Torn dust boots allow water and abrasive dirt to enter, causing wear in the ball seats. Corrosion on adjustment sections makes wheel alignment difficult; contact with obstacles can permanently deform the rod. However, these symptoms can also be caused by faulty wheel bearings, kingpin bearings or suspension components.

1. Secure the vehicle against movement. Check tyre pressures, ride height and vehicle loading in accordance with the specified measurement conditions. Inspect dust boots, rod bodies, clamp connections and locking devices for cracks, rust and displacement.
2. Have a second technician make small steering movements under the specified loading conditions. Observe each joint individually for delayed movement and relative displacement. Keep hands clear of pinch points.
3. Measure axial and radial joint play with a dial indicator under the specified test load. Compare the readings with the manufacturer's limits; tilting movement in a ball joint does not automatically indicate wear. Check wheel bearings and kingpin bearings separately.
4. Measure individual and total toe using calibrated wheel alignment equipment, including wheel runout compensation. Assess the readings against the vehicle specification: zero toe is not correct for every version.

Replace deformed or cracked track rods; straightening, welding or heating is not an acceptable repair. Fit separate track rod ends only where the design allows it and the threads and clamping surfaces are undamaged. If adjustment connections are seized by corrosion, replacing the complete assembly prevents unreliable clamping. Use a suitable ball joint separator and protect adjacent dust boots.

Replicate the original length only as a starting point for installation. Observe the minimum thread engagement, specified tightening torques and locking method; replace single-use fasteners. Check the boots for twisting and freedom of movement at full steering lock. Then align the relevant axles and check the steering wheel centre position and, where specified, steering angle sensor calibration. Release the vehicle only after a final inspection and a safe road test.