MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 1
Innovative Braking and Controls Worldwide
Boosted Master Cylinders
hydraulically boosted straight bore, tandem,
and two-stage master cylinders
Versatile,
High-performance
Hydraulic Brake Actuators
2 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Why choose MICO?
MICO, Inc. designs, manufactures and markets
hydraulic components, controls, and brake systems
primarily for off-road markets. We have manufacturing
facilities in:
• North Mankato, Minnesota U.S.A.
• Ontario, California U.S.A.
• Empalme, Sonora, Mexico
Many of the world’s largest off-highway OEMs value
the knowledgeable staff at MICO and work with us to
make their products better. Our custom-engineered
products are designed with the customer requirements
as the primary driver. It is our intent to help custom-
ers build their systems with our expertise in hydraulic
components, braking systems and controls.
Our goal is to meet or exceed our customers’
expectations in every aspect of our business.
Product lines we specialize in include:
• Actuators
• Brake Locks
• Brakes
• Controls
• Cylinders
• Electrohydraulics
• Master Cylinders
• Valves
MICO is proud to be ISO 9001 and ISO 14001 certied
and continuously strive for improvement while remain-
ing a quality leader in our eld. We have been a suc-
cessful business for over 60 years. Privately owned,
customer driven. We look forward to working with you!
Boosted Master Cylinders
The same dependability and performance that goes
into every MICO Braking System Product also goes into
our versatile, high-performance MICO
®
Boosted Master
Cylinders. This is an important consideration when you
select a source of supply for your uid power needs.
The MICO
®
Boosted Master Cylinders presented in
this catalog are designed for use in machines that are
equipped with other hydraulic power devices. This
design feature eliminates the need for a separate
system to provide power for the boosted master cylinder.
The MICO
®
Boosted Master Cylinders combine a
booster section (see page 4 and 5) with a master
cylinder section (see pages 6 through 9) in a single unit.
The booster section utilizes power from a vehicles
existing open center or load sensing hydraulic system
to boost the master cylinder section. The booster sec-
tion will typically use mineral base hydraulic oil, while
the master cylinder will use DOT brake uid. However,
models exist that can use mineral base hydraulic oil in
both sections.
The MICO
®
Boosted Master Cylinders provides the
machine operator a pedal feel directly proportional to
the brake pressure, and therefore, provides excellent
modulation.
The master cylinder section of the actuator remains
manually functional in the event of main power sys-
tem loss, or "power-off." A power-off brake apply does
require greater pedal force and pedal travel than during
power-on apply.
Complete the appropriate Application Data Sheet online,
www.mico.com. The MICO Applications Department will
analyze your specications and based on your input
recommend a boosted master cylinder suitable for your
requirements.
This document is intended to provide general information about MICO Products. MICO, Inc. has attempted to present accurate information
about MICO Products in its catalogs, brochures, and other printed materials. MICO, Inc. is not responsible for errors, inaccuracies, or
inconsistencies that may exist in any catalog brochure or other printed materials or any damages arising from or related to reliance on
information in them. Materials and specications for MICO Products set forth in catalogs, brochures, and other printed materials are subject
to change without notice or obligation. Refer to www.mico.com for the most recent versions of our literature. If you have any questions
concerning MICO Products, please contact MICO, Inc. All MICO Products and service are sold and provided subject to the MICO Warranty at
www.mico.com in effect on the date of sale or supply.
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 3
Applications
Forestry Equipment
Agricultural Equipment
Heavy Construction
Equipment
Mining Equipment
In-Plant & Warehouse
Equipment
Service & Utility
Vehicles
Catalog Index
Why choose MICO ............................................................................................... 2
Operation of Boosted Master Cylinders..............................................................4-5
Operation of Master Cylinder Sections ...............................................................6-9
Boosted Straight Bore Master Cylinders ........................................................ 10-11
Boosted Straight Bore Master Cylinders
(stem seal type) ......................................................................................12-13
Boosted Tandem Straight Bore Master Cylinders
(stem seal type) ......................................................................................14-15
Boosted Two-Stage Master Cylinders ............................................................16-17
Hydraulic Power Brake Actuator .....................................................................18-19
Boosted Open Center Master Cylinder...........................................................20-21
Boosted Dual Master Cylinder ........................................................................22-23
Conversion Factors ............................................................................................. 24
Useful Formulas .................................................................................................. 25
4 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Operation of Boosted Master Cylinders
Non-Actuated Position
(Refer to Figure 1)
The master cylinder section is not actuated and remains
in the static condition without mechanical force being
applied to the input piston (3).
In the neutral (non-actuated) condition, uid from the
vehicle’s hydraulic system ows unrestricted through the
booster section. Hydraulic uid enters the inlet port (1),
ows across piston lands (2) on input piston (3), through
boost piston ow ports (4) into chamber (6), and exits
the booster through outlet port (7).
1. The booster operates on the principle of restricting
uid ow past piston lands (2) to create a higher
pressure on the inlet side of boost piston (5) com-
pared to the output side of boost piston (5). This is
“pressure drop.”
Due to ow and pressure drop characteristics of uid in
the booster section, the booster is designed to operate
between 3 and 10 GPM unless otherwise noted.
1. It is likely that ow less than 3 GPM may not pro-
duce sufcient pressure drop for adequate boost.
2. Flow above 10 GPM may produce too much pres-
sure drop through the booster section.
A. Too much pressure drop through the booster
can cause the booster section to hydraulically
begin to “self energize” before the brake pedal
is applied. This condition may also prevent the
brake system from fully releasing.
B. Flow over 10 GPM will waste hydraulic energy
and cause the hydraulic system to operate at
higher temperatures.
Forward Movement of Brake Pedal Until
Fully Applied
(Refer to Figure 2)
As the operator applies the brake pedal, boost piston (3)
begins to move forward and compress spring (10). Pis-
ton lands (2) begin to close causing restricted uid ow
and a build-up of pressure on inlet port side of boost
piston (5).
This pressure moves boost piston (5) forward. Forward
movement of boost piston (5) causes pistons (9, 11 &
12) to move forward and force uid to the brakes.
1. The area of boost piston (5) is much larger than
master cylinder piston (12), therefore, the uid
pressure being forced to the brakes is much
higher than the pressure in boost chamber (8).
Brake system pressure in the master cylinder reacts
against the area of reaction piston (9) and is transmitted
mechanically to the brake pedal. This reaction provides
the operator with a modulated “feel” of brake system
pressure.
1. Pedal feed-back can be ne tuned to meet special
application requirements by changing the diameter
of reaction piston (9). The larger reaction piston (9),
the higher the pedal effort necessary to achieve
brake system pressure.
Continued forward pedal movement increases the
restriction of ow at piston lands (2) and causes the
increasing pressure in booster chamber (8) to move
boost piston (5) forward. As pedal effort increases, this
process continues until pressure in booster chamber (8)
reaches the booster internal relief valve (13) setting. The
relief valve pressure setting is preset at the factory.
With no additional forward movement of input piston
(3), the pressure and spring forces will equalize and
boost piston (5) will stop in this position. At this point the
booster has reached the maximum boosting capabil-
ity. Only the additional pedal effort by the operator can
further increase brake pressure by mechanically moving
the pistons forward.
Hydraulic system uid ows through the booster section
to outlet port (7) and through the remaining hydraulic
circuit. Because the booster works on the principal of
pressure drop, the resultant pressure of a power
beyond device does not affect output pressure from the
boosted master cylinder to the brakes. However, a relief
valve must be present in the hydraulic system between
the boosted master cylinder and power beyond device.
This relief valve must open at a lower pressure than the
system main relief valve to maintain the proper pressure
drop.
Brake Pedal Released
(Refer to Figure 3)
When pedal force is removed from the input piston (3)
the booster section and master cylinder section begin to
release brake system pressure and return to the neutral
(non-actuated) condition.
Springs (14 & 15) force input piston (3) back. Piston
lands (2) and ow ports (4) open. Flow restriction is
instantly removed and pressure in booster chamber (8)
equalizes with the pressure in chamber (6).
Hydraulic system ow continues to enter inlet port (1)
and exit outlet port (7).
The master cylinder section returns to the non-actuated
position.
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 5
(1) Inlet Port
(2) Piston Lands
(3) Input Piston
(4) Flow Ports
(5) Boost Piston
(6) Chamber
(7) Outlet Port
(8) Booster Chamber
(9) Reaction Piston
(10) Spring
(11) Output Piston
(12) Master Cylinder Piston
(13) Internal Relief Valve
(14) Spring
(15) Spring
Callout Key
FIGURE 1
FIGURE 2
FIGURE 3
6 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Operation of Master Cylinder Sections
Function of Residual Check Valves
The cylinders listed in this catalog are available with
or without a residual check valve. Be sure to use the
proper cylinder for your application.
Residual check valves are normally used in drum
brake systems to hold a slight pressure (approxi-
mately 8-16 PSI) in the vehicle brake system while
the brake pedal is released. This residual pressure
is retained to air the lip of the cup seal in the wheel
cylinder to prevent leakage and/or air ingestion into
the brake system.
Residual check valves are not used in disc brake
systems. Residual pressure in a disc brake system
will hold the brake pads in contact with the rotor disc,
resulting in brake drag, over-heating of brake com-
ponents, unnecessary wear and premature brake
replacement.
Operation of Straight Bore Master Cylinders
(Refer to Figure 4)
The single piston straight bore type master cylinder has
been proving its usefulness since the early 1930’s and is
still in extensive use.
With brakes completely released (no input force on
brake pedal), the cylinder is at reservoir or atmospheric
pressure. Initial brake actuation forces piston (1) and
primary cup (2) down the cylinder bore (3) closing off the
equalizing port (5). This completely seals uid between
the master cylinder and the brake cylinder.
(see pages 10 & 11)
The reaction piston (6) is forced against the booster
section input piston and generates a modulated pedal
feel. This force is proportional to the output pressure of
the master cylinder.
Continued brake pedal movement will now cause an
increase in uid pressure, transmitted to the brake
cylinders. Releasing the force on the brake pedal allows
uid to ow back to the cylinder bore (3) and ultimately
to the reservoir (4).
(1) Piston
(2) Primary Cup
(3) Cylinder Bore
(4) Reservoir
(5) Equalizing Port
(6) Reaction Piston
Callout Key
FIGURE 4
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 7
Operation of Master Cylinder Sections
Operation of Tandem Master Cylinder
(Refer to Figure 5)
The tandem master cylinder was developed as a result
of regulations governing brake systems on highway
vehicles. Many off-road vehicles also use this type
cylinder. These cylinders provide two independent
master cylinder sections in a common housing.
When the cylinder is at rest, the primary and secondary
sections are directly communicated to the reservoirs,
allowing, to a degree, purging of residual air and pres-
sure equalization.
Initial brake actuation forces front piston (1) to contact
the primary seat (2) pressurizing the primary bore (9). As
pressure increases, the secondary piston (8) is hydrauli-
cally driven forward. The secondary stem (5) contacts
the secondary seat (6) and the secondary bore (7) is
pressurized. Both bores are equally pressurized as the
cylinder is stroked.
The reaction piston (11) is forced against the booster
section input piston and generates a modulated pedal
(see pages 14 & 15)
feel. This force is proportional to the pressure in primary
bore (9). Since there are no equalizing ports for the
high pressure cups to pass, primary check valve (3) and
secondary check valve (4) open during return stroke of
cylinder allowing a rapid smooth return of both pistons.
Releasing the force on the brake pedal allows uid to
ow back to the primary and secondary bores (9 & 7)
and back to the reservoir.
In the event of a primary section malfunction, the
primary piston (10) will mechanically drive the secondary
piston (8) forward. The foot pedal will drop due to
the approximately 0.7 inch of internal piston travel
before secondary system pressure is reached.
If a secondary section malfunction occurs, the primary
piston (10) will hydraulically drive the secondary piston
(8) until it bottoms out. The primary bore (9) will then
pressurize upon continued pedal travel.
(1) Front Piston
(2) Primary Seat
(3) Primary Check Valve
(4) (Secondary Check Valve
(5) Secondary Stem
(6) Secondary Seat
(7) Secondary Bore
(8) Secondary Piston
(9) Primary Bore
(10) Primary Piston
(11) Reaction Piston
Callout Key
FIGURE 5
Residual Check Valve and
Outlet Ports are not shown.
8 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Operation of Master Cylinder Sections
Operation of Straight Bore Master Cylinders (stem seal type) (see pages 12 & 13)
(Refer to Figure 6)
By eliminating the equalizing port normally found on
master cylinders, this cylinder offers simplicity, ease of
bleeding and versatility. The lack of a compensating port
allows the cylinder to be used in a broad range of
applications indiscriminative of volumetric output.
With no input force on brake pedal the cylinder is at
reservoir or atmospheric pressure. Initial brake actua-
tion forces secondary piston (2) into the contact seat
(3). Continuation of brake actuation force will begin to
pressurize the uid at the output port. The pressure is
communicated to the reaction piston (1) and the result-
ing force is directed back through the booster section
input piston and to the vehicle pedal. This action
provides the operator with modulated pedal feel
proportional to the system pressure.
Upon release of the brake pedal, the primary piston (4)
returns and bottoms out on the cylinder housing.
Fluid displaced from the reservoir is now forced back
into the reservoir. The secondary piston (2) is forced
back to the retaining ring and the primary seat (3) is
open to reservoir or atmospheric pressure.
(1) Reaction Piston
(2) Secondary Piston
(3) Seat
(4) Primary Piston
Callout Key
FIGURE 6
Residual Check Valve is not
shown.
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 9
Operation of Master Cylinder Sections
Operation of Two-Stage Master Cylinders (see pages 16 & 17)
(Refer to Figure 7)
With no input force from the brake pedal, the cylinder
uid is at reservoir pressure throughout. The relief valve
piston (1) is closed, reservoir port (2) is open and high
pressure piston (9) is open at seat (11).
Initial brake pedal actuation forces the low pressure
piston (5) to move the low pressure cup (3) past the
reservoir port (2). Continued pedal movement causes
uid in the low pressure bore (10) and high pressure
bore (6) to become pressurized, forcing uid to exit the
outlet port. The reaction piston (4) is forced against the
booster section input piston and generates modulated
brake pedal feel. This force is proportional to the pres-
sure in high pressure bore (6). Continued pedal move-
ment will force the high pressure piston (9) against seat
(11). The pressurized uid will then be directed over the
high pressure cup (7), through ow-through hole (8) and
out through outlet port.
Low pressure displacement will continue until pressure
in the brake system is greater than the relief valve pres-
sure setting. Pressure is sensed at the outlet port and
communicated to the relief valve piston (1) via the tube
assembly (12).
When the relief valve piston (1) opens, pressurized uid
in low pressure bore (10) ows directly to reservoir.
Due to the pressure drop in the low pressure bore (10)
the high pressure cup (7) ares, sealing any ow from
low pressure bore (10) to high pressure bore (6). At the
same time high pressure piston (9) fully seals to seat
(11). Further cylinder displacement to outlet port is con-
tinued by the ow from high pressure bore (6) only.
Releasing the force on the brake pedal allows cylinder
components to return to a static position and uid to ow
back to reservoir.
(1) Relief Valve Piston
(2) Reservoir Port
(3) Low Pressure Cup
(4) Reaction Piston
(5) Low Pressure Piston
(6) High Pressure Bore
(7) High Pressure Cup
(8) Flow Through Hole
(9) High Pressure Piston
(10) Low Pressure Bore
(11) Seat
(12) Tube Assembly
Callout Key
FIGURE 7
10 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted
Straight Bore
Master Cylinders
FEATURES
y Provides natural pedal "feel" through hydraulic
reaction
y Completely hydraulic - no vacuum or air assist
required
Style A
(diaphragm reservoir)
Style B
(dual ller caps)
Style C
(single ller cap)
Residual valve used where required.
Exhaust venting hole is normally in down position
to prevent moisture contamination.
NOTE: Dimensions vary slightly between units and are used for reference purposes only. Go to www.mico.com/service-literature/installa-
tion-drawing-search to view dimensional installation drawings. If the drawing is not available, contact MICO for more information.
millimeters
inches
SPLIT FLANGE
MODELS
02-460-218
02-460-308
SEMI-SPLIT
FLANGE MODELS
02-460-304
Model No. 02-460-216 shown
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 11
Model No. 02-460-216 shown
SPECIFICATIONS
NOTE: Whilesomemodelnumbersmayhaveidenticalspecications,theremaybedifferencesinttings,portsizesandllerplugs.
Go to www.mico.com/service-literature/installation-drawing-search and enter the model number for more information. If the drawing
is not available, contact MICO for more information.
Model
Number
Style
(see top of
page 10)
Brake
Line
Pressure
(PSI)
Master
Cylinder
Bore
Diameter
Master
Cylinder
Fluid
Displacement
Push Rod
Force with
Boosted Power
Push Rod
Force for
500 PSI
without
Boosted Power
Booster Pressure
Differential at
Maximum Brake
Line Pressure
Master
Cylinder
Fluid
Type
Uses a
Residual
Check
Valve
02-460-216 C 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF Yes
+ 02-460-218
C 0 - 1365 1.500 in 2.40 in
3
700 lb @ 1365 PSI 960 lb 280 PSI @ 6 GPM BF Yes
02-460-238 C 0 - 1350 1.250 in 1.67 in
3
360 lb @ 1350 PSI 690 lb 210 PSI @ 10 GPM BF Yes
02-460-244 C 0 - 1500 1.250 in 1.67 in
3
200 lb @ 1500 PSI 690 lb 285 PSI @ 10 GPM BF Yes
02-460-248 C 0 - 1500 1.250 in 1.67 in
3
375 lb @ 1500 PSI 690 lb 260 PSI @ 10 GPM BF Yes
02-460-264 B 0 - 900 1.750 in 3.27 in
3
500 lb @ 900 PSI 1275 lb 290 PSI @ 5 GPM BF Yes
02-460-266 B 0 - 1500 1.750 in 3.27 in
3
375 lb @ 1500 PSI 1275 lb 535 PSI @ 6 GPM BF Yes
02-460-268 B 0 - 1500 1.750 in 3.27 in
3
375 lb @ 1500 PSI 1275 lb 535 PSI @ 6 GPM BF No
02-460-280 A 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF Yes
+ 02-460-304 C 0 - 1150 1.500 in 2.40 in
3
310 lb @ 1150 PSI 960 lb 280 PSI @ 6 GPM BF Yes
02-460-306 C 0 - 1365 1.500 in 2.40 in
3
700 lb @ 1365 PSI 960 lb 280 PSI @ 6 GPM BF Yes
+ 02-460-308
C 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 365 PSI @ 10 GPM BF Yes
02-460-310 C 0 - 1400 1.250 in 1.67 in
3
760 lb @ 1400 PSI 690 lb 170 PSI @ 6 GPM BF Yes
● 02-460-334
C 0 - 900 1.500 in 2.40 in
3
260 lb @ 900 PSI 960 lb 245 PSI @ 10 GPM BF Yes
02-460-368 C 0 - 570 1.500 in 2.40 in
3
140 lb @ 570 PSI 960 lb 162 PSI @ 8 GPM BF Yes
02-460-416 C 0 - 1800 1.500 in 2.40 in
3
910 lb @ 1800 PSI 960 lb 365 PSI @ 10 GPM BF Yes
02-460-436 C 0 - 750 1.500 in 2.40 in
3
300 lb @ 750 PSI 960 lb 175 PSI @ 10 GPM BF Yes
02-460-478 C 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF Yes
♦ 02-460-480 B 0 - 1500 2.250 in 5.41 in
3
375 lb @ 1500 PSI 2060 lb 910 PSI @ 7 GPM BF Yes
02-461-216 C 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF No
02-461-244 C 0 - 1500 1.250 in 1.67 in
3
200 lb @ 1500 PSI 690 lb 285 PSI @ 10 GPM BF No
02-461-248 C 0 - 1500 1. 250 in 1.67 in
3
375 lb @ 1500 PSI 690 lb 260 PSI @ 10 GPM BF No
02-461-280 A 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF No
● 02-461-334
C 0 - 900 1.500 in 2.40 in
3
260 lb @ 900 PSI 960 lb 245 PSI @ 10 GPM BF No
♦ 02-461-480 B 0 - 1500 2.250 in 5.41 in
3
375 lb @ 1500 PSI 2060 lb 910 PSI @ 7 GPM BF No
NOTES:
All model numbers have a ow capacity of 3 to 10 GPM unless noted otherwise.
All model numbers have a main hydraulic system pressure of 0 to 2000 PSI unless noted otherwise.
All model numbers have a 1.62 inch push rod travel unless noted otherwise.
BF = DOT 3, 4, 5 and 5.1 brake uid.
Flow capacity is 3 to 12 GPM.
● Main hydraulic system pressure is 0 - 3000 PSI.
+ Split ange (see details on page 10).
♦ Master cylinder has a bleeder screw. It appears similar to Style A on page 12.
12 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted
Straight Bore
Master Cylinders
(stem seal type)
FEATURES
y Provides natural pedal "feel" through hydraulic
reaction
y Completely hydraulic - no vacuum or air assist
required
y May be used for spring brake applications
y Easy to bleed
Style A
(dual ller caps)
Style B
(single ller cap)
Residual valve used where required.
Exhaust venting hole is normally in down position
to prevent moisture contamination.
NOTE: Dimensions vary slightly between units and are used for reference purposes only. Go to www.mico.com/service-literature/installa-
tion-drawing-search to view dimensional installation drawings. If the drawing is not available, contact MICO for more information.
millimeters
inches
Model No. 02-460-272 shown
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 13
Model No. 02-460-272 shown
SPECIFICATIONS
NOTE: Whilesomemodelnumbersmayhaveidenticalspecications,theremaybedifferencesinttings,portsizesandllerplugs.
Go to www.mico.com/service-literature/installation-drawing-search and enter the model number for more information. If the drawing
is not available, contact MICO for more information.
Model
Number
Style
(see top of
page 12)
Brake
Line
Pressure
(PSI)
Master
Cylinder
Bore
Diameter
Master
Cylinder
Fluid
Displacement
Push Rod
Force with
Boosted Power
Push Rod
Force for
500 PSI
without
Boosted Power
Booster Pressure
Differential at
Maximum Brake
Line Pressure
Master
Cylinder
Fluid
Type
Uses a
Residual
Check
Valve
02-460-272 B 0 - 1500 1.500 in 2.40 in
3
375 lb @ 1500 PSI 960 lb 360 PSI @ 8 GPM BF Yes
02-460-318 B 0 - 900 1.750 in 3.27 in
3
500 lb @ 900 PSI 1275 lb 290 PSI @ 5 GPM BF Yes
02-460-390 B 0 - 1500 1.250 in 1.67 in
3
200 lb @ 1500 PSI 690 lb 285 PSI @ 10 GPM BF No
02-460-394 B 0 - 1150 1.500 in 2.40 in
3
300 lb @ 1150 PSI 960 lb 290 PSI @ 8 GPM HO No
02-460-396 B 0 - 1150 1.500 in 2.40 in
3
300 lb @ 1150 PSI 960 lb 290 PSI @ 8 GPM BF No
02-460-398 B 0 - 1650 1.500 in 2.40 in
3
420 lb @ 1650 PSI 960 lb 420 PSI @ 10 GPM BF No
02-460-428 B 0 - 1350 1.250 in 1.67 in
3
203 lb @ 1350 PSI 690 lb 240 PSI @ 10 GPM BF Yes
02-460-430 B 0 - 1550 1.500 in 2.40 in
3
400 lb @ 1550 PSI 960 lb 370 PSI @ 10 GPM HO No
02-460-468 B 0 - 1600 1.750 in 3.27 in
3
805 lb @ 1600 PSI 1275 lb 610 PSI @ 10 GPM BF Yes
02-460-496 B 0 - 900 1.500 in 2.40 in
3
260 lb @ 900 PSI 960 lb 240 PSI @ 10 GPM HO Yes
02-460-626 B 0 - 1500 1.250 in 1.67 in
3
375 lb @ 1500 PSI 690 lb 260 PSI @ 10 GPM BF Yes
02-461-496 B 0 - 900 1.500 in 2.40 in
3
260 lb @ 900 PSI 960 lb 240 PSI @ 10 GPM HO No
NOTES:
All model numbers have a ow capacity of 3 to 10 GPM unless noted otherwise.
All model numbers have a main hydraulic system pressure of 0 to 2000 PSI unless noted otherwise.
All model numbers have a 1.62 inch push rod travel unless noted otherwise.
BF = DOT 3, 4, 5 and 5.1 brake uid. HO = mineral base hydraulic oil.
14 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted Tandem
Straight Bore
Master Cylinders
(stem seal type)
FEATURES
y Provides natural pedal "feel" through hydraulic
reaction
y Two independent master cylinders and
reservoir ports in a common housing
y Provides braking in the event either the front
or rear brakes become inoperative
y Completely hydraulic - no vacuum or air assist
required
y Uses a remote uid reservoir for ease of
monitoring uid level
Residual valve used where required.
Exhaust venting hole is normally in down position
to prevent moisture contamination.
NOTE: Dimensions vary slightly between units and are used for reference purposes only. Go to www.mico.com/service-literature/installa-
tion-drawing-search to view dimensional installation drawings. If the drawing is not available, contact MICO for more information.
millimeters
inches
Model No. 02-460-380 shown
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 15
Model No. 02-460-380 shown
SPECIFICATIONS
NOTE: Whilesomemodelnumbersmayhaveidenticalspecications,theremaybedifferencesinttings,portsizesandllerplugs.
Go to www.mico.com/service-literature/installation-drawing-search and enter the model number for more information. If the drawing
is not available, contact MICO for more information.
Model
Number
Brake
Line
Pressure
(PSI)
Master
Cylinder
Bore
Diameter
Master
Cylinder
Fluid
Displacement
Push Rod
Force with
Boosted Power
Push Rod
Force for
500 PSI
without
Boosted Power
Booster Pressure
Differential at
Maximum Brake
Line Pressure
Master
Cylinder
Fluid
Type
Uses
Residual
Check
Valves
▲ 02-460-256
0 - 1500 1.250 in
0.84 - 0.68 in
3
55 - 45 split
375 lb @ 1500 PSI 702 lb 250 PSI @ 8 GPM BF
Yes (1)
02-460-360 0 - 900 1.750 in
1.62 - 1.62 in
3
50 - 50 split
500 lb @ 900 PSI 1312 lb 290 PSI @ 5 GPM BF Yes
▲ 02-460-374
0 - 1500 1.250 in
0.84 - 0.68 in
3
55 - 45 split
375 lb @ 1500 PSI 702 lb 250 PSI @ 8 GPM BF Yes
● 02-460-380 0 - 1600 1.750 in
1.92 - 1.31 in
3
60 - 40 split
420 lb @ 1600 PSI 1312 lb 535 PSI @ 10 GPM BF Yes
● 02-460-404 0 - 1550 1.750 in
1.62 - 1.62 in
3
50 - 50 split
390 lb @ 1550 PSI 1312 lb 535 PSI @ 10 GPM BF Yes
02-460-410 0 - 1230 1.750 in
1.62 - 1.62 in
3
50 - 50 split
350 lb @ 1230 PSI 1312 lb 420 PSI @ 10 GPM BF No
02-460-476 0 - 900 1.750 in
1.62 - 1.62 in
3
50 - 50 split
270 lb @ 900 PSI 1312 lb 320 PSI @ 10 GPM HO No
02-460-494 0 - 550 1.750 in
1.62 - 1.62 in
3
50 - 50 split
295 lb @ 550 PSI 1312 lb 185 PSI @ 10 GPM HO No
02-460-602 0 - 900 1.750 in
1.62 - 1.62 in
3
50 - 50 split
490 lb @ 900 PSI 1312 lb 320 PSI @ 10 GPM HO No
▲ 02-461-256
0 - 1500 1.250 in
0.84 - 0.68 in
3
55 - 45 split
375 lb @ 1500 PSI 702 lb 250 PSI @ 8 GPM BF No
▲ 02-461-374
0 - 1500 1.250 in
0.84 - 0.68 in
3
55 - 45 split
375 lb @ 1500 PSI 702 lb 250 PSI @ 8 GPM BF No
● 02-460-404 0 - 1550 1.750 in
1.62 - 1.62 in
3
50 - 50 split
390 lb @ 1550 PSI 1312 lb 535 PSI @ 10 GPM BF No
NOTES:
All model numbers have a ow capacity of 3 to 10 GPM unless noted otherwise.
All model numbers have a main hydraulic system pressure of 0 to 2000 PSI unless noted otherwise.
All model numbers have a 1.62 inch push rod travel unless noted otherwise.
BF = DOT 3, 4, 5 and 5.1 brake uid. HO = mineral base hydraulic oil.
Master cylinder has integral reservoirs.
● Main hydraulic system pressure is 0 - 3000 PSI.
▲ Push rod travel is 1.49 inch.
Only the secondary outlet port has residual check valve.
16 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted
Two-Stage
Master Cylinders
FEATURES
y Provides natural pedal "feel" through hydraulic
reaction
y Completely hydraulic - no vacuum or air assist
needed
y Provides high brake system pressure in the
event of inadequate booster pressure
Residual valve used where required.
Exhaust venting hole is normally in down position
to prevent moisture contamination.
NOTE: Dimensions vary slightly between units and are used for reference purposes only. Go to www.mico.com/service-literature/installa-
tion-drawing-search to view dimensional installation drawings. If the drawing is not available, contact MICO for more information.
millimeters
inches
Model No. 02-460-300 shown
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 17
Model No. 02-460-300 shown
SPECIFICATIONS
NOTE: Whilesomemodelnumbersmayhaveidenticalspecications,theremaybedifferencesinttings,portsizesandllerplugs.
Go to www.mico.com/service-literature/installation-drawing-search and enter the model number for more information. If the drawing
is not available, contact MICO for more information.
Model
Number
Brake
Line
Pressure
(PSI)
Master
Cylinder
Bore
Diameter
Master
Cylinder
Fluid
Displacement
Push Rod
Force with
Boosted Power
Push Rod
Force for
500 PSI
without
Boosted Power
Booster Pressure
Differential at
Maximum Brake
Line Pressure
Master
Cylinder
Fluid
Type
Uses a
Residual
Check
Valve
02-460-276 0 - 1500 1.750 in / 1.000 in 1.1 - 2.2 in
3
375 lb @ 1500 PSI 470 lb 135 PSI @ 8 GPM BF Yes
02-460-294 0 - 1500 1.750 in / 1.125 in 1.4 - 2.3 in
3
375 lb @ 1500 PSI 570 lb 185 PSI @ 8 GPM BF Yes
02-460-300 0 - 1500 2.250 in / 1.250 in 1.7 - 3.5 in
3
375 lb @ 1500 PSI 690 lb 250 PSI @ 8 GPM BF Yes
02-460-346 0 - 1150 1.750 in / 1.125 in 1.4 - 2.3 in
3
460 lb @ 1150 PSI 570 lb 119 PSI @ 3.5 GPM BF Ye s
02-460-432 0 - 1500 1.750 in / 0.875 in 0.9 - 3.5 in
3
215 lb @ 1500 PSI 375 lb 122 PSI @ 3 GPM HO No
02-460-450 0 - 1500 1.750 in / 1.000 in 1.1 - 2.2 in
3
130 lb @ 1500 PSI 470 lb 170 PSI @ 8 GPM BF Yes
02-460-466 0 - 1500 1.750 in / 1.000 in 1.1 - 2.2 in
3
375 lb @ 1500 PSI 470 lb 135 PSI @ 8 GPM BF Yes
02-461-294 0 - 1500 1.750 in / 1.125 in 1.4 - 2.3 in
3
375 lb @ 1500 PSI 570 lb 185 PSI @ 8 GPM BF No
02-461-450 0 - 1500 1.750 in / 1.000 in 1.1 - 2.2 in
3
130 lb @ 1500 PSI 470 lb 170 PSI @ 8 GPM BF No
NOTES:
All model numbers have a ow capacity of 3 to 10 GPM unless noted otherwise.
All model numbers have a main hydraulic system pressure of 0 to 2000 PSI unless noted otherwise.
All model numbers have a 1.62 inch push rod travel unless noted otherwise.
BF = DOT 3, 4, 5 and 5.1 brake uid. HO = mineral base hydraulic oil.
18 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Hydraulic
Power Brake
Actuator
DESCRIPTION AND OPERATION
The MICO compact size Hydraulic Power Brake Actua-
tor is designed for use with vehicles that are equipped
with an open center hydraulic system that can supply
0.7 to 4 GPM at 335 PSI to obtain the set brake limit
pressure.
The Hydraulic Power Brake Actuator combines a
hydraulically boosted power section with a master
cylinder section in a single unit. This valve uses
mineral based hydraulic oil in both the booster and
master cylinder sections. The master cylinder section
is separate from the booster portion so an alternate
uid such as transmission oil can be used for the
brakes. However, DOT brake uid cannot be used.
A hydraulic feedback system within the valve gives the
operator pedal feel directly proportional to the brake
pressure, thus providing excellent modulation.
The master cylinder can be operated manually through
the booster during power-off conditions. Brake pres-
sure developed without boost assist will depend on the
push rod force applied.
Residual valve used where required.
NOTE: Dimensions vary slightly between units and are used for reference purposes only. Go to www.mico.com/service-literature/installa-
tion-drawing-search to view dimensional installation drawings. If the drawing is not available, contact MICO for more information.
millimeters
inches
Model No. 02-460-454 shown
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 19
Model No. 02-460-454 shown
Model
Number
Brake
Line
Pressure
(PSI)
Master
Cylinder
Bore
Diameter
Master
Cylinder
Fluid
Displacement
Push Rod
Force with
Boosted Power
Push Rod
Force for
500 PSI
without
Boosted Power
Booster Pressure
Differential at
Maximum Brake
Line Pressure
Master
Cylinder
Fluid
Type
Uses
Residual
Check
Valve
02-460-454 1100 1.061 in 1.1 in
3
250 lb @ 1100 PSI 510 lb 335 PSI HO No
02-460-488 700 1.061 in 1.1 in
3
175 lb @ 700 PSI 510 lb 210 PSI HO Yes
02-460-606 1350 1.061 in 1.1 in
3
235 lb @ 1350 PSI 510 lb 367 PSI HO Yes
NOTES:
All model numbers have a 1.3 inch push rod travel unless noted otherwise.
HO = mineral base hydraulic oil.
SPECIFICATIONS
NOTE: Whilesomemodelnumbersmayhaveidenticalspecications,theremaybedifferencesinttings,portsizesandllerplugs.
Go to www.mico.com/service-literature/installation-drawing-search and enter the model number for more information. If the drawing
is not available, contact MICO for more information.
20 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted Open Center
Master Cylinder
DESCRIPTION
The MICO Open Center Master Cylinder, also
called MICO Open Center Valve, permits the ad-
dition of a power braking system to vehicles which
are equipped with other hydraulic power devices
such as power steering or implements.
Through the use of the boosted open center master
cylinder, power from the main open center hydrau-
lic system can be used to operate the vehicle’s
brakes, eliminating the need of any other power
brake unit.
Design of the boosted open center master cylinder
insures a natural pedal feel. The reaction of the
pedal against the driver’s foot is directly proportion-
al to the hydraulic pressure in the wheel cylinders
which actuate the brakes.
The boosted master cylinder permits the brake
system to develop up to double the amount of
hydraulic pressure present in the main hydraulic
system. For example, 52 bar (750 PSI) in the main
system can deliver 103 bar (1500 PSI) to the brake
cylinders.
In the event hydraulic system pressure is lost, the
master cylinder can be actuated mechanically
through the booster at an unassisted level.
FEATURES
• Eliminates the need of a separate power
brake unit
• Provides natural pedal “feel” through
hydraulic reaction
• Pressure in the brake system can be double
that of the main hydraulic system
• Full hydraulic ow and pressure are
retained for downstream components, except
for the small volume required to displace brake
cylinder pistons during brake applications
Typical Circuit Schematic
MICO
Boosted
Open Center
Master Cylinder
Relief
Valve
To Power
Beyond
Pump
Filter
Single
Brake
System
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 21
Typical model show. Dimensions may vary slightly between units.
millimeters
inches
Model
Number
Maximum Brake
Pressure Setting
PSI
Flow Capacity
GPM
Brake
Port
06-460-522
1850 50
3-24 9/16-18UNF
06-460-642
1550 50
3-24 1/2-20UNF
06-460-656
1500 50
3-24 1/2-20UNF
06-460-658
1850 50
3-24 1/2-20UNF
06-460-660
1150 50
3-24 1/2-20UNF
06-460-662
1550 50
3-24 9/16-28UNF
06-460-666
950 50
3-24 9/16-18UNF
06-460-668
1000 50
3-12 1/2-20UNF
06-460-672
750 50
3-24 1/2-20UNF
06-460-676
1550 50
3-12 9/16-18UNF
06-460-684
1100 50
3-12 1/2-20UNF
Normally used with disc brakes (no residual check valve)
Consult MICO Applications Department for other available models.
NOTE:AllmodelshaveSAE#10pressureports,owthroughportsandreturnports.
SPECIFICATIONS
System pressure ............................................. 0 to 2000 PSI
Master cylinder, bore & stroke ................................. 1.62 in x 1.50 in
Master cylinder, capacity ............................................. 3.1 in
3
Push rod travel with power ................................approximately 0.2 in
Push rod force with power. . . . . . . . . . . . . . . . . . 340 lb at 1500 PSI brake line pressure
Push rod travel without power ............................approximately 1.844 in
Push rod force without power ............................... 1500 lb at 725 PSI
Consult MICO for application detail.
TechnicalDataforanyspecicmodelfurnisheduponrequest.
PERFORMANCE DATA
22 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
Boosted Dual
Master Cylinder
Intended for Brake systems with Brake Assisted Steering
DESCRIPTION
The MICO® Boosted Dual Master Cylinder is used
to modulate output pressures up to 1500 PSI. This
is used in conjunction with properly sized brakes
using mineral base oils and booster oil from a
standby pressure source such as that of a trans-
mission. This unique integrated design can easily
adapt to many dual systems to provide steering
assist power braking with one pedal applied or
full power braking with both pedals applied giving
equally balanced brake pressures.
The MICO Boosted Dual Master Cylinder can be
used in a number of hydraulic systems where a
constant ow of 0.7 to 1.5 GPM can be provided for
each side with inlet boost pressures controlled up
to 450 PSI.
FEATURES
• Power-off braking through master cylinders
• Open center spool construction provides
smooth brake modulation at all pressures
• Direct acting pistons provide pedal feel
accurately representing brake pressures
• Balance piston seals uid loss from one master
cylinder side should the opposite side brake line
become severed
• Reduced pedal force during steering assist
braking
• Compact integrated design for use in restricted
spaces
• Internal pressure balancing piston provides
allowance for pedal offset
• Master cylinder design promotes bleeding
without the use of bleeder screws
• All connections are SAE o-ring boss for leakage
integrity
• Master cylinder for use with mineral base oils
only
Typical Circuit Schematic
MICO
Boosted Dual
Master Cylinder
SW
Rear
Brakes
SW
A
A
TT
T
P
P
Relief
Valve
Pump
Implement
Valve
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 23
Typical model show. Dimensions
may vary slightly between units.
millimeters
inches
SPECIFICATIONS
Booster pressure .............................................. to 450 PSI
Brake line pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . to 1500 PSI
Master cylinder displacement ....................................... to 1.1 in
3
Effective booster area .............................................. 3.35 in
2
Master cylinder area ............................................... 0.99 in
2
Maximum pressure equalization displacement ........................... 0.13 in
3
Becausethismastercylinderisapplicationspecic,consultMICO,Inc.fordetails,
optionsandmodications.
PERFORMANCE DATA
Consult MICO Applications Department for available models.
24 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
CONVERSION FACTORS
TORQUE
lbft lbin daNm Nm kgm
1 12 0.13556 1.356 0.1382
0.08333 1 0.01130 0.1130 0.01152
7.376 88.51 1 10 1.019
0.7376 8.851 0.1 1 0.102
7.2359 86.80 0.9806 9.806 1
PRESSURE
PSI MPa bar kPa kg/mm
2
kg/cm
2
1 0.006895 0.06895 6.895 0.0007031 0.07031
145 1 10 1000 0.102 10.20
14.50 0.1 1 100 0.0102 1.02
0.145 0.001 0.01 1 0.000102 0.0102
1422 9.807 98.07 9807 1 100
14.22 0.09807 0.9807 98.07 0.01 1
1 Atmosphere = 14.7 lb/in
2
1 Atmosphere = 29.92 inches of Mercury
1 Atmosphere = 33.96 ft of water
1 inch of Mercury = 0.491 lb/in
2
= 13.6 inches of water
1 PSI = 2.0416 inches of Mercury at 62 F
ENEGRY
ftlb kgfm kWhr hphr
J
1 0.1383 3.766e-7 5.051e-7 1.356
7.233 1 2.724e-6 3.653e-6 9.806
2655224 367098 1 1.341 3600000
1980000 273745 0.7457 1 2684520
0.7376 0.1020 2.778e-7 3.725e-7 1
1 BTU = British thermal unit = heat required to raise
temperature of 1 lb of water 1 F
1 BTU = 778.17 ftlb
m/sec ft/s km/hr MPH ft/min
1 3.281 3.6 2.237 196.85
0.3048 1 1.097 0.6818 60
0.2778 0.9113 1 0.6214 54.68
0.4470 1.467 1.609 1 88
0.00508 0.01667 0.01829 0.01136 1
VELOCITY
cm in ft m km mile
1 0.3937 0.03281 0.01 0.00001 0.000006
2.54 1 0.08333 0.0254 0.000024 0.000017
30.48 12 1 0.3048 0.0003 0.000186
100 39.37 3.281 1 0.001 0.000621
100,000 39,370 3281 1000 1 0.6214
160,934 63,360 5280 1609 1.609 1
LENGTH
VOLUME
in
3
cm
3
L qt
1 16.39 0.01639 0.01732
0.06102 1 0.001 0.001057
61.02 1000 1 1.057
57.75 946.4 0.9464 1
1 U.S. gallon = 231 in
3
1 U.S. gallon = 0.13368 ft
3
FLOW
GPM in
3
/s L/min
1 3.850 3.785
0.260 1 0.983
0.264 1.017 1
FORCE
N lb
1 0.2248
4.4482 1
ACCELERATION
ft/s
2
in/s
2
m/s
2
cm/s
2
1 12 0.3048 30.48
0.08333 1 0.0254 2.54
3.281 39.37 1 100
0.03281 3937 0.01 1
AREA
in
2
cm
2
mm
2
1 6.452 645.2
0.1550 1 100
0.001550 0.01 1
POWER
hp kW
methp
1 0.7457 1.014
1.341 1 1.360
0.9863 0.7355 1
1 hp = 550 ftlb/s
1 hp = 33,000 ftlb/min
1 hp = 42.44 BTU/min
TEMPERATURE
F = (C x 1.8) + 32
C = (F - 32) 1.8
MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13 25
USEFUL FORMULAS
Piston Area (in
2
) = � (3.1416) x r
2
(in)
Area (in
2
)
Piston Radius (in) =
� (3.1416)
Force (lb) = Piston Area (in
2
) x Line Pressure (PSI)
Force (lb)
Piston Area (in
2
) =
Line Pressure (PSI)
Force (lb)
Line Pressure (PSI) =
Piston Area (in
2
)
Volume (in
3
) = Piston Area (in
2
) x Stroke (in)
Volume (in
3
)
Piston Area (in
2
) =
Stroke (in)
Volume (in
3
)
Stroke (in) =
Piston Area (in
2
)
Volume (gallons) = Flow Rate (GPM) x Time (min)
Volume (gallons)
Flow Rate (GPM) =
Time (min)
Volume (gallons)
Time (minutes) =
Flow Rate (GPM
Pump Displacement (cir) x Pump RPM
Flow Rate (GPM) =
231
Flow Rate (GPM) x 231
Pump displacement (cir) =
Pump RPM
Flow Rate (GPM) x 231
Pump RPM =
Pump Displacement (cir)
PTO/Pump RPM = PTO % Engine Speed x Engine RPM
PTO/Pump RPM
PTO % Engine Speed =
Engine RPM
PTO/Pump RPM
Engine RPM =
PTO % Engine Speed
Flow Rate (GPM) x Line Pressure (PSI)
Horsepower =
1714 x % Pump Efciency
Torque (lbft) x RPM
Horsepower =
5252
Horsepower x 5252
Torque (lbft) =
RPM
Horsepower x 5252
RPM =
Torque (lbft)
cir = cubic inches per revolution
231 cubic inches = 1 U.S. gallon
26 MICO, Inc. Form No. 84-460-007 Online Revised 2013-09-13
MICO, Incorporated
1911 Lee Boulevard
North Mankato, MN U.S.A. 56003-2507
Tel: +1 507 625 6426 Fax: +1 507 625 3212
Web Site: www.mico.com
MICO is a trademark and registered trademark of
MICO, Inc. MICO is registered in the U.S. Patent and
Trademark Ofce as well as in Australia, Canada,
Indonesia, Japan, Peoples Republic of China, South
Korea, and the European Community.
PRODUCT LINE:
Brakes
Caliper Disc Brakes
Multiple Disc Brakes
Brake Locks
Electric
Mechanical
Controls
Electronic Controls
Hydraulic Throttle Controls
Pedal Controls
Switches
Transducers/Sensors
Cylinders
Drive Axle Brake Actuators
Slave Cylinders
Wheel Cylinders
Master Cylinders
Boosted Cylinders
Hydraulically and Air Actuated
Straight Bore Cylinders
Two-Stage Cylinders
Valves
Accumulator Charging
Electrohydraulic Brake
Park Brake
Pressure Modulating
Miscellaneous Components
In-line Residual Check Valves
Pump with Integrated Valves
Reservoirs
Form No. 84-460-007 Online Revised 2013-09-13 Printed in U.S.A.
