Finding the Right Auger for a 2016 Hyundai R55-9A

[MikePhua]

The Hyundai R55-9A and Its Compact Excavator Legacy
The Hyundai R55-9A is a 5.5-ton class compact excavator introduced in the mid-2010s as part of Hyundai’s push into the premium mini-excavator market. Known for its smooth hydraulic control, fuel-efficient Tier 4 Final engine, and spacious cab, the R55-9A quickly gained traction among utility contractors, landscapers, and municipal fleets. Hyundai Construction Equipment, a division of Hyundai Heavy Industries founded in 1985, has sold millions of machines worldwide, with the R55 series contributing significantly to its compact equipment portfolio.
With an operating weight of approximately 12,000 lbs and a digging depth of over 12 feet, the R55-9A offers the versatility needed for trenching, grading, and light demolition. Its auxiliary hydraulic circuit makes it compatible with a wide range of attachments—including augers, which are essential for post-hole digging, foundation piers, and tree planting.
Terminology Clarification

• Auger: A helical drilling tool used to bore holes into soil, clay, or rock, typically powered by hydraulic flow from the excavator.
  
• Flow rate: The volume of hydraulic fluid delivered per minute, measured in gallons per minute (GPM), critical for auger motor performance.
  
• Pressure rating: The hydraulic system’s maximum operating pressure, measured in pounds per square inch (PSI), which determines torque output.
  
• Mounting bracket: The interface between the auger drive and the excavator’s boom or coupler.
  
• Hex shaft: A common output shaft shape on auger drives, used to connect various bit sizes securely.
  

Matching an Auger to the R55-9A’s Hydraulic Specs
The R55-9A’s auxiliary hydraulic circuit typically delivers around 20–24 GPM at pressures up to 3,000 PSI. These specs place it squarely in the mid-range auger compatibility zone. Auger drives designed for 3–6 ton excavators are ideal, offering enough torque for 12–36 inch bits depending on soil conditions.
Recommended auger drive specs:

• Flow range: 15–30 GPM
  
• Pressure rating: 2,500–3,500 PSI
  
• Output shaft: 2" hex or 2.5" round
  
• Mounting: Excavator-specific bracket or universal quick attach
  

Brands like Digga, Auger Torque, and Blue Diamond offer models tailored to compact excavators. For example, Digga’s PD6 drive unit is often paired with machines in the R55 class and supports bits up to 36 inches in diameter.
Soil Conditions and Bit Selection
Choosing the right auger bit depends heavily on soil type:

• Clay and loam: Standard earth bits with replaceable teeth
  
• Sandy soil: Bits with wider flighting to prevent collapse
  
• Rocky terrain: Tungsten carbide teeth and pilot points
  
• Frost or asphalt: Rock heads or core barrels with heavy-duty cutting edges
  

In Michigan, a landscaping crew using an R55-9A reported success with 18-inch bits in clay-rich soil for fence post installation. However, when working near Lake Erie, they switched to rock heads due to embedded gravel and glacial till.
Mounting and Hydraulic Hookup Tips
Proper mounting ensures safe operation and minimizes wear. Most auger drives come with a universal bracket, but custom mounts may be needed for tight boom geometries or coupler systems.
Installation checklist:

• Verify bracket compatibility with R55-9A’s coupler
  
• Use high-pressure hydraulic lines rated for 3,000 PSI
  
• Install quick couplers with dust caps to prevent contamination
  
• Route hoses to avoid pinch points during boom articulation
  
• Test flow direction to ensure correct auger rotation
  

Some operators install a case drain line to relieve excess pressure, especially when using high-torque drives. This prevents seal blowouts and extends motor life.
Buying New vs. Used Auger Systems
New auger systems offer warranty coverage, updated designs, and compatibility assurance. Prices range from $2,500 to $6,000 depending on drive size, bit selection, and mounting hardware. Used systems can be found for $1,000–$3,000 but require careful inspection.
Used equipment checklist:

• Inspect motor housing for cracks or leaks
  
• Check shaft wear and spline integrity
  
• Test hydraulic rotation under load
  
• Verify bracket welds and pin fitment
  
• Confirm bit condition and tooth wear
  

A contractor in Ohio purchased a used auger drive for his R55-9A and discovered a cracked motor casing after two weeks. The repair cost nearly matched the original purchase price, underscoring the importance of thorough inspection.
Auger Alternatives and Specialty Attachments
While augers are ideal for vertical boring, some operators consider alternatives for specialized tasks:

• Cone splitters for log processing
  
• Trenchers for shallow utility runs
  
• Post drivers for fencing
  
• Core barrels for foundation drilling
  

These attachments often share hydraulic requirements with augers and can be interchanged using the same auxiliary circuit. However, mounting and control systems may differ, requiring additional setup.
Conclusion
Pairing a hydraulic auger with a 2016 Hyundai R55-9A is a practical upgrade that expands the machine’s capabilities across landscaping, utility, and construction tasks. With a flow rate of 20–24 GPM and robust auxiliary hydraulics, the R55-9A supports mid-range auger drives capable of tackling diverse soil conditions. Whether buying new or used, attention to hydraulic specs, mounting compatibility, and soil type ensures optimal performance and long-term reliability. From Michigan’s clay fields to rocky slopes in Colorado, the right auger turns a compact excavator into a precision drilling tool.