A utility infrastructure contractor in Germany learned a costly lesson in 2023 when two CAT M323F wheeled excavators began showing erratic swing bearing behavior — the superstructure was sluggish to initiate swing and made grinding noise at low swing speed. The swing bearing seals had deteriorated, allowing abrasive road grit to enter the bearing race. Wheeled excavators spend far more time traveling on public roads than their tracked counterparts, meaning the swing bearing seal system faces constant contamination exposure that tracked machines in a quarry never encounter. Replacing the swing bearing seals: €380 per machine. Replacing a contaminated swing bearing: €12,000-18,000 per machine.
Wheeled excavators are specialized machines designed for urban utility work, road maintenance, and infrastructure projects where tracked excavators would damage paved surfaces or be too slow traveling between work points. They add road-travel capability — and with it, rubber components that tracked excavators don’t need: pneumatic tires, road-going suspension rubber, and outrigger systems. They also need more robust sealing for components exposed to road contamination during travel phases.
This guide covers the rubber parts specific to wheeled excavators from the major manufacturers: Caterpillar M323/M330 series, Liebherr A914/A918/A924 series, and Komatsu PW148/PW160/PW220 series.
Need wheeled excavator rubber components? Request a quote from Babacan Group — we stock components for all major wheeled excavator brands.
Swing Bearing Seals: The Critical Road-Travel Component
The swing bearing (slew ring) allows the excavator superstructure to rotate 360°. On tracked excavators working in a quarry, the bearing is exposed to rock dust. On a wheeled excavator traveling daily on public roads, the bearing seal faces road grit, water spray, and road chemical contamination at higher intensity.
Swing Bearing Lip Seal Specifications
The outer and inner lip seals of the swing bearing must:
– Exclude abrasive particles smaller than 0.1 mm (fine road grit particle size)
– Withstand the pressure of water spray during road travel at 40-70 km/h
– Maintain sealing function through repeated thermal cycles (ambient to operating temperature)
– Not cause excessive drag on the bearing rotation (sealing force balanced against friction)
Wheeled excavator swing bearing seal compound: High-quality polyacrylate (ACM) or FKM for the outer lip — better abrasion resistance than standard NBR and improved resistance to road salt and de-icing chemicals.
Swing Bearing Inner Seal (Grease Retention)
The inner seal retains the bearing lubricant. On wheeled excavators doing road travel, centrifugal effects during travel (when the superstructure is locked but vibrates with road inputs) can cause inner seal leakage that doesn’t occur in quarry excavators. A compromised inner seal accelerates bearing fatigue by reducing the lubricant film.
Outrigger System Rubber Components
Wheeled excavators deploy outrigger stabilizers (typically four) before beginning excavating work, lifting the machine off its tires to provide a stable platform. The outrigger system uses rubber components throughout:
Outrigger Pad Rubber Faces
The outrigger feet are typically steel plates with rubber faces that:
– Protect paved surfaces from the steel outrigger foot
– Distribute the load to reduce point loading on asphalt
– Provide slight compliance for leveling on uneven surfaces
Outrigger pad rubber: High-durometer NR or polyurethane, Shore A 65-75. The compound must resist compression under the full machine tipping load. On a 20-tonne wheeled excavator at maximum reach, a single outrigger can carry 25+ tonnes — requiring substantial rubber compression capacity.
Outrigger Cylinder End Cushions
At the end of outrigger extension travel, rubber cushions stop the cylinder and absorb the kinetic energy of the extending beam. These cushions:
– Are compressed at every outrigger deployment
– Must handle repeated high-force impacts without fatigue cracking
– Service life: Often overlooked; typically 3,000-5,000 deployment cycles
Outrigger Frame Rubber Isolators
Between the outrigger frame and the machine chassis, rubber isolators prevent outrigger-generated vibration from transmitting into the chassis during excavating work. These provide a secondary isolation layer beyond the outrigger pad rubber itself.
Tire and Axle System Rubber
Wheeled excavators use pneumatic tires (typically heavy-duty construction tires, not highway tires) and axle systems derived from heavy truck designs.
Front Axle Suspension Rubber
Most wheeled excavators use a front independent suspension with rubber springs or coil springs plus rubber bump stops. The rubber elements here:
– Absorb road shock during travel at 30-70 km/h
– Maintain ground contact on rough road surfaces for stable travel
– Provide slight leveling capability when deploying outriggers on slightly uneven ground
CAT M323F front axle suspension rubber specifications are based on the front axle assembly carrying the attachment weight (standard front attachment plus dipper arm: approximately 2,500 kg) plus the front portion of the machine. This is significantly more load than a typical truck front axle.
Rear Axle Drive Axle Rubber
Wheeled excavators with 4WD (available on all major wheeled excavator lines for off-road travel) use rubber-isolated rear axle mounting similar to backhoe loaders. The rear drive axle pivot rubber allows slight axle articulation for uneven ground clearance during site travel.
Steering System Rubber Components
Wheeled excavators use a conventional steering system for road travel and may use the outriggers for position adjustment during excavating. The steering column and steering cylinder use rubber seals and damping components:
– Steering cylinder seals: Must be rated for the full hydraulic steering pressure (140-160 bar)
– Steering column vibration isolator: Prevents road vibration from transmitting to the steering wheel
Engine and Superstructure Mounting
The superstructure of a wheeled excavator is mechanically similar to its tracked counterpart. Engine mount specifications are comparable to tracked excavators of the same size.
Engine Mount Differences from Tracked Machines
On a tracked excavator, the engine is mounted in the superstructure which sits on rubber-isolated track frames. On a wheeled excavator, the superstructure sits on the carrier through the swing bearing only — there is no secondary isolation layer from a track frame. This means:
- Engine vibration transmitted to the swing bearing is higher than in tracked equivalents
- Swing bearing seals must handle a combined vibration load from both engine vibration and road travel
- Engine mount quality has a more direct impact on swing bearing longevity in wheeled excavators
For CAT wheeled excavator engine mounts (M323/M330 series), see our comprehensive CAT excavator rubber parts guide for compound and specification details applicable to the wheeled variants.
Superstructure Frame Anti-Vibration Mounts
The counterweight attachment and boom foot plate on wheeled excavators use the same rubber cushion mounts as tracked versions. However, road travel subjects these mounts to additional cyclic fatigue from road-frequency vibration transmitted through the swing bearing — shortening their service life relative to quarry-based tracked machines.
Cab Isolation for Urban Work
Wheeled excavators work in urban environments where cab noise level is as important as vibration isolation. Road-adjacent utility excavation often occurs near residential buildings — the machine’s internal noise level affects operator communication and creates an impression of professionalism (or otherwise) to bystanders.
Cab Mounting System
Liebherr’s A-series wheeled excavators use a floating cab mounting system with six rubber isolation mounts. The cab isolation on Liebherr A918 is notably softer than equivalent tracked A918 machines because the operating environment (urban paved surfaces, low ground vibration) requires lower frequency isolation.
The Liebherr A924 (24-tonne class) uses a cab suspension system similar to Liebherr’s larger excavators — the heavier cab mass requires different mount stiffness than the A918 even though the operating environment is the same. For a complete guide to Liebherr excavator rubber parts including the A-series, see our Liebherr excavator rubber parts guide.
Noise Isolation Rubber Components
Urban wheeled excavator cabs use additional acoustic isolation rubber at structural penetrations:
– Hydraulic hose entry grommets
– Control linkage pass-throughs
– Electrical conduit entry points
These grommets must be maintained in condition — a split grommet at any penetration point creates an acoustic short-circuit that significantly raises interior cab noise level.
Road Travel Considerations for Rubber Longevity
Wheeled excavators traveling at highway speeds (up to 70 km/h on CAT M323F) generate road vibration spectra that tracked machines never experience. Some observations:
- Swing bearing seal fatigue: At 70 km/h, the superstructure (locked during travel) vibrates at road excitation frequencies (5-30 Hz). This creates cyclic fatigue in the swing bearing seal lip that doesn’t occur during stationary excavating work
- Engine mount road-frequency loading: Road-frequency inputs add to engine vibration cycling in engine mounts, potentially shortening life compared to tracked equivalents
- Cab mount cumulative loading: Urban utility contractors may travel 30-50 km per day to reach job sites — cab mount fatigue accumulates from road travel as well as excavating work
For vibration isolation principles and how road travel vibration spectra differ from excavating vibration, our anti-vibration mount selection guide provides useful technical background.
Komatsu PW Series Specific Notes
The Komatsu PW148/PW160/PW220 wheeled excavators are popular in European utility infrastructure markets. Notable rubber part considerations:
- PW148-11 and PW160-11: Use Komatsu’s SAA4D107 engine (AGCO Power derived). Engine mounts are similar to equivalent Komatsu PC-series tracked machines but with slightly softer front mounts to account for the wheeled machine’s higher road-travel vibration input.
- PW220-11: The larger wheeled excavator uses a 6-cylinder SAA6D107E-3 and has a more sophisticated cab isolation system with additional rear cab mounts. For full Komatsu excavator rubber parts guidance, see our Komatsu excavator rubber parts guide.
Babacan Group manufactures wheeled excavator rubber components under ISO 9001:2015 quality management. Browse our rubber mounts catalog or request a technical quote for your specific model.
Replacement Intervals
| Component | Tracked Equiv. | Wheeled (road-intensive) |
|---|---|---|
| Swing bearing seals | 5,000-8,000 hrs | 3,000-5,000 hrs |
| Engine mounts | 4,000-6,000 hrs | 3,500-5,000 hrs |
| Cab isolation mounts | 3,000-5,000 hrs | 2,500-4,000 hrs |
| Outrigger pad rubber | N/A | 1,500-3,000 deployments |
| Outrigger cylinder cushions | N/A | Annual or 3,000 deployments |
| Axle suspension rubber | N/A | 4,000-6,000 hrs |
| Steering cylinder seals | 3,000-5,000 hrs | 3,000-5,000 hrs |
Conclusion
Wheeled excavators are tracked excavator technology adapted for urban and road-adjacent applications — but the road-travel capability changes the rubber maintenance picture significantly. Swing bearing seal integrity, outrigger system rubber, and cab isolation for both excavating and road-travel vibration all require attention that tracked-excavator maintenance programs don’t address.
Key takeaways:
– Swing bearing seals on wheeled excavators face road grit contamination that tracked machines don’t — use higher-specification seal compounds and inspect more frequently
– Outrigger pad rubber and cushions are high-cycle wear items often overlooked in maintenance planning
– Road travel at 40-70 km/h adds fatigue loading to all rubber components not present in quarry-based tracked machines
– Wheeled excavator engine mounts must be rated for both excavating vibration and road-frequency inputs simultaneously
Babacan Group ships wheeled excavator rubber parts to utility contractors and excavator dealers in 84+ countries. Request a technical quote for your CAT M, Liebherr A, or Komatsu PW model.