Last updated on December 16th, 2025 at 09:31 am
Now that we’ve explored different types of steering systems, their components, and how they work, it’s time to bridge theory with practice. In this final post of our steering series, we’ll focus on calculating hydraulic steering unit displacement: a critical calculation that determines which steering unit is right for your machine and how well it will perform.
Whether you’re designing a tractor, loader, or any wheeled off-road equipment, one fundamental question always comes up: What steering unit displacement do I need? The answer isn’t a guess, it’s a calculation based on your machine’s steering requirements.
Let’s break down this essential calculation step-by-step.
Steering Unit Displacement
Now that we’ve explored different types of steering systems, their components, and how they work, it’s time to bridge theory with practice. In this final post of our steering series, we’ll focus on calculating hydraulic steering unit displacement: a critical calculation that determines which steering unit is right for your machine and how well it will perform.
Whether you’re designing a tractor, loader, or any wheeled off-road equipment, one fundamental question always comes up: What steering unit displacement do I need? The answer isn’t a guess, it’s a calculation based on your machine’s steering requirements.
Let’s break down this essential calculation step-by-step.
Indian Farmer working with Tractor
Why Steering Unit Displacement Matters
The steering unit displacement (measured in cm³/rev or in³/rev) defines how much hydraulic oil the steering unit can deliver with each revolution of the steering wheel. This directly impacts:
Steering responsiveness – How quickly your wheels turn
Lock-to-lock turns – How many times you need to turn the wheel fully from left to right
Steering wheel effort – The force needed to steer the machine
System efficiency – Whether your steering pump is undersized or oversized
A steering unit with too small displacement will require excessive steering wheel rotations, making the machine tedious to operate. Too large a displacement will waste pump flow and energy, making the steering feel sluggish or overly sensitive.
The trick is finding the right balance for your specific application.
The Step-by-Step Calculation Process
Calculating steering unit displacement involves understanding three core parameters:
Step 1: Determine Your Required Steering Cylinder Stroke
Start by identifying your steering cylinder’s total stroke length. This is the distance the cylinder piston travels from one end to the other (fully extended to fully retracted).
For example, if you’re designing a tractor with a steering cylinder that has a stroke of 80 mm, that’s your baseline. This dimension is based on your machine’s geometry and axle design specifically, how much the wheels need to move sideways to achieve your desired steering angle.
Step 2: Calculate Total Cylinder Volume Movement
Next, multiply your cylinder stroke by the piston area (diameter²) to get the total volume of oil needed to move the cylinder fully from lock-to-lock.
The formula is straightforward:
Total Volume = Cylinder Area × Stroke Length
This gives you the total amount of hydraulic oil (in cm³) required to steer your machine from full left lock to full right lock.
Step 3: Decide on Lock-to-Lock Steering Wheel Rotations
Here’s where you define the user experience. How many times should an operator turn the steering wheel to go from full left lock to full right lock?
Typical agricultural tractors: 4-6 turns
Quick-steer loaders: 2-3 turns
Articulated vehicles with steering amplifiers: 1-2 turns
Fewer rotations make steering faster and easier but less precise. More rotations give finer control but require more operator effort.
Step 4: Calculate the Required Steering Unit Displacement
Now you can determine what displacement your steering unit needs. The formula is:
Steering Unit Displacement = Total Cylinder Volume ÷ Number of Lock-to-Lock Turns
This tells you exactly how much oil (in cm³/rev) your steering unit must deliver with every single rotation of the steering wheel.
A Real-World Example
Understanding the methodology is important, but seeing it applied in real-time is even more powerful.
I’ve created a comprehensive video that walks through these exact calculations step-by-step, showing you how to use each variable and understand the relationships between steering angle, cylinder displacement, and machine type. The video demonstrates:
How different machine types (tractors, loaders, excavators) require different displacements
Real supplier catalog values and how to match them to your calculations
How steering wheel input (RPM) translates to steering circuit flow requirements
The complete workflow from concept to final steering unit selection
Try the Interactive Calculator: https://calculator.epichydraulic.com/calculators/steering/hydraulic-steering-calculator
The calculator does the heavy lifting for you. Instead of manually working through formulas, simply input:
Your steering cylinder dimensions
Desired lock-to-lock turns
Steering wheel rotational speed
And instantly get:
Required steering unit displacement
Actual lock-to-lock turns available from standard units
Steering circuit flow requirements
Real supplier catalog matches
This calculator has helped engineers, technicians, and designers quickly validate their steering system concepts and avoid costly design errors.
Bringing It All Together
Throughout this seven-part series, we’ve journeyed through the complete world of hydraulic steering:
Part 2: Types of steering systems (open center, closed center, load sensing)
Part 6: Off-road steering systems across different equipment
Part 7: Making it practical—calculations and selection
You now understand not just how hydraulic steering works, but why it works that way. You can appreciate the engineering decisions behind every component, from the gerotor assembly to the load-sensing relief valve. And most importantly, you have the tools to calculate and select the right steering unit for any application.
What’s Next?
Whether you’re an engineer designing your next machine, a technician troubleshooting steering performance, or simply someone curious about how the machines around you actually work, the steering calculator is here to help you verify your designs and make confident decisions.
Access the Steering Calculator Now →
Steering is more than just turning wheels: it’s a sophisticated balance of hydraulic engineering, mechanical design, and operator experience. I hope this series has given you deeper insight into one of the most critical systems in mobile equipment.
If you’ve made it through all seven parts of this steering series, I truly appreciate your interest in understanding hydraulics at this level. Your curiosity drives me to keep creating content that breaks down complex systems into understandable pieces.
If you’d like to stay updated on future hydraulic topics, please subscribe. I’m 100% planning to dive deeper into hydraulics and break it down into simple terms for you. There’s so much more ground to cover—from pump sizing and valve selection to system optimization and troubleshooting.
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