Parts & attachments
HOREY BZZ1 Steering Unit
The HOREY BZZ1 is an open-centre, non-reaction hydraulic steering unit. HOREY gives tractors, loaders and road rollers as typical uses. The generic BZZ table runs from 50 to 1000 ml/rev with recommended flows of 4 to 75 L/min, a 16 MPa maximum inlet and a 2.5 MPa continuous return limit. Getting a match starts with the circuit type your machine uses, then the displacement, the steering-column coupling and the port threads. This page covers the function codes, how recommended flow is worked out, the port and column options, manual steering, and what to send for a quote.
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Build my procurement briefChoose the circuit type first
BZZ is a family name. The function code tells you which steering circuit the unit is built for, and it must match the rest of the machine's hydraulics. If that machine also runs a hydraulic drive, HOREY's BMR orbital motors can go on the same enquiry, and its other components are grouped in our parts and attachments category.
| Function code | What it means for your order |
|---|---|
| 1: open-centre, non-reaction | In neutral the pump flow returns to tank, which suits a fixed-displacement pump. The BZZ1 symbol shows P, T, A and B ports. |
| 2: open-centre, reaction | A different circuit in the same code map. Specify it by name if your machine needs reaction steering, and ask for its schematic. |
| 3: closed-centre, non-reaction | The inlet is closed in neutral, which suits a variable-displacement pump. Changing from open to closed centre is a circuit redesign; ask HOREY for the engineering response. |
| 5: load-sensing | Works with a priority valve and load signal line. Ask for the full schematic and supply requirements of the selected unit. |
Recommended flow and size
HOREY's footnote sets recommended flow at 1.25 times the theoretical flow at 60 steering-wheel revolutions per minute. For a 200 ml/rev unit: 200×60/1000 = 12 L/min, times 1.25 gives the listed 15 L/min. Use it to size the pump supply; actual steering speed on the machine also depends on cylinders and load. If the same pump also feeds a drive motor, such as one of HOREY's BMS orbital motors, size the supply for both loads.
| Displacement | Recommended flow, mass, length L |
|---|---|
| 50 ml/rev | 4 L/min recommended; 4.72 kg; L 140 mm. |
| 100 ml/rev | 7.5 L/min; 5.27 kg; L 145 mm. |
| 160 ml/rev | 12 L/min; 5.75 kg; L 153 mm. |
| 200 ml/rev | 15 L/min; 6.08 kg; L 158 mm. |
| 315 ml/rev | 24 L/min; 7.13 kg; L 174 mm. |
| 500 ml/rev | 38 L/min; 8.67 kg; L 197 mm. |
| 1000 ml/rev | 75 L/min; 12.8 kg; L 262 mm. |
Published specifications
Read each value with its stated conditions, and ask the manufacturer for any limit not listed here.
| Specification | Published value | Meaning / limit |
|---|---|---|
| Function | BZZ1: open-centre, non-reaction [1] [2] [4] | Codes 2, 3 and 5 in the same code map are other circuit types: open-centre reaction, closed-centre and load-sensing. |
| Displacement / recommended flow (generic table) | 50–1000 ml/rev / 4–75 L/min by size [5] | The table covers the BZZ range as a whole; check that your size is offered as a BZZ1. Flow is worked out from steering-wheel speed. |
| Pressure limits (generic table) | 16 MPa maximum inlet; 2.5 MPa maximum continuous return [5] | P and T each have their own limit. Check both against your tractor's pump and return line. |
| Column connections | A long cross-slot; B SAE involute spline; C short cross-slot [2] [6] | These letters describe the steering-column coupling, separate from the hydraulic A/B cylinder ports. |
| Standard and low-input-torque versions | Standard version with tractor/loader/roller examples; D low-input-torque option [3] | HOREY's example for the D option is forklift steering on flat ground; tractors use the standard version. |
Hydraulic port codes and column fixing threads
In HOREY's port table, the main column gives the P, T, A and B hydraulic ports. The C and V columns are fixing threads for the column mounting. Some codes use different threads on A/B than on P/T.
| Port code | Threads and what to check |
|---|---|
| Default | M20×1.5 main ports; fixing threads C = M10 and V = M12. Give your column drawing with the order. |
| Port code B | G1/2 main ports; fixing C = M10, V = M10×1. This port code B is a different thing from column connection B, the spline. |
| Port code C | 3/4-16UNF O-ring main ports; fixing threads 3/8-16UNC and 3/8-24UNF. Confirm thread and seal type on the drawing. |
| Port codes R and S | P/T are M22×1.5 and A/B are M18×1.5; S is the O-ring version. Plan adapters for both thread sizes. |
| Depths and length | Main ports are 14 mm deep and fixing threads 16 mm. The connection drawing gives length L and the column-coupling reference for spline or cross-slot engagement. |
Steering effort and manual mode
HOREY says that with normal oil supply the steering-column torque is no more than 5 N·m. If supply is lost, the unit works as a hand pump, with much higher effort and a stated maximum input of 120 N·m. How well a loaded tractor steers in that mode depends on axle load, tyres, ground and cylinder size.
HOREY's feature table lists tractors, loaders and road rollers for the standard version and uses forklift steering on flat ground as the example for the low-input-torque D option. Include axle load, tyre and ground conditions, cylinder layout and the available supply and return with your enquiry. HOREY does not publish steering angle, turns lock to lock or tested effort in manual mode.
The four-port symbol shows the unit's own function. External protection, supply and other vehicle-side requirements belong to the machine circuit and need to be specified with it.
What to send for a steering-unit quote
A displacement number alone is not enough for HOREY to quote the right unit. Send the four groups of information below together. A machine that needs a parking brake on its drive can have HOREY's ZBMR brake motors priced in the same request.
Machine and circuit
The tractor or other machine, the circuit type (open or closed centre, reaction or not), the steering cylinders and the working conditions.
Hydraulic conditions
Pump flow and pressure available, return line conditions and the steering duty. Check them against the 16 MPa inlet and 2.5 MPa continuous return limits.
Physical interfaces
The steering-column coupling and fixing drawing, mounting, P/T/A/B port threads, space envelope and full option code.
Documents back from HOREY
The configuration table, circuit, current instructions and HOREY's assessment for your machine, including how manual mode will perform.
Buyer questions
Can another BZZ function code replace a BZZ1?
Only if your circuit changes to match. Code 1 is open-centre non-reaction, 2 is open-centre reaction, 3 is closed-centre and 5 is load-sensing; the code must fit the machine's hydraulics. [1] [2] [4]
Why is 15 L/min recommended for a 200 ml/rev unit?
HOREY's footnote uses 60 wheel rpm and a 1.25 factor: 200×60/1000 = 12 L/min, times 1.25 = 15 L/min. [5]
Prepare a model-specific brief
Write your actual conditions below. This local worksheet is not sent, uploaded or saved after reload. Copy or print it before leaving.
Sources
Specifications come from the manufacturer's publications listed below, with the date each was checked.
- HOREY BZZ1 open-centre non-reaction page
manufacturer · Checked 2026-10-12
BZZ1 product page with an explanation of BZZ1/2/3 circuits, column torque in normal use and manual mode.
- Original BZZ order-code diagram
manufacturer · Checked 2026-10-12
Function codes 1, 2, 3 and 5, the 16 MPa class and A/B/C column connection letters.
- Original BZZ feature and port-code table
manufacturer · Checked 2026-10-12
Tractor, loader and roller uses, the low-input-torque D option, main port codes and C/V fixing threads with 14/16 mm depths.
- Original BZZ1 hydraulic-function symbol
manufacturer · Checked 2026-10-12
Hydraulic symbol for the BZZ1 with P/T and A/B ports.
- Original generic BZZ technical table
manufacturer · Checked 2026-10-12
Displacement 50–1000 ml/rev, recommended flow 4–75 L/min, 16 MPa inlet, 2.5 MPa continuous return and masses, with the flow formula in a footnote.
- Original BZZ connection drawing and length table
manufacturer · Checked 2026-10-12
Short, long and spline column connections, length L, P/T/A/B layout and fifteen lengths by size.
Report a correction through our contact form, quoting HOREY BZZ1 Steering Unit and the relevant specification.