Tilton Brake Proportioning Valve (98-1261) - Manual

How It works
Tilton Engineering’s patented, adjustable hydraulic brake proportioning valve enables the driver,
or a crew member, to adjust the brake-force to a particular wheel (or wheels). The light, rugged
valve may be bulkhead or panel-mounted. The proportioning valve can also be used effectively
with dual master cylinder systems.
The proportioning valve is often one of the less understood devices bolted onto a racecar.
Understanding how it works from a functional standpoint will allow the driver and crew chief to
take advantage of its properties for a better racecar setup.
At lower pressures, the Tilton proportioning valve acts as a simple hydraulic connector.
The pressure going into the proportioning valve is equal to the pressure going out. There is a 1:1
ratio between inlet and outlet pressure. The 45º line shown in Chart 1 and Chart 2 indicates this
pressure range. Once a certain pressure limit is reached, a further increase in line pressure occurs
at a reduced rate of 3:1 from inlet to outlet.
The adjustment control alters the point at which the inlet/outlet pressure ratio changes from 1:1
to 3:1. For example, look at the proportioning valve Midpoint Position of Chart 1 for Screw-type
proportioning valves and Position 4 of Chart 2 for Lever-type proportioning valves. When the
master cylinder line (inlet) pressure is above 650 PSI, the caliper line (outlet) pressure is below
the pressure in the master cylinder line. The sloping line off to the right (shown in Chart 1 & 2)
demonstrates this. Below 650 PSI they are equal.
The dual-slope line gives the proportioning valve one advantage over the balance bar system. It
can be tuned for a better front-to-rear brake balance under both light and heavy braking. A par-
ticular setting of the balance bar gives you a set front-to-rear brake balance, such as 70/30 (70%
front/30% rear). Under both light and heavy braking, this balance remains the same. However, the
loading on the front and rear axles does not remain the same under different braking conditions.
During heavy braking, there is a large load transfer from the rear to the front axle. As the load
increases on the front axle you want a higher percentage of the braking force on the front axle.
The bend in the graph for the proportioning valve allows this to happen when the proportioning
valve is placed in the line for the rear calipers. During heavier braking, a higher percentage of the
braking force is distributed to the front calipers.
InstallatIon notes
Position 7
Position 6
Position 5
Position 4
Position 3
Position 2
Position 1
1000 1200 800 600 400 200
200
400
600
800
1000
1200
Inlet Pressure (PSI)
O
utlet P
ressur
e
(PSI
)
Maximum
Compression
Midpoint of
Compression
Minimum
Compression
1000 1200 800 600 400 200
200
400
600
800
1000
1200
Inlet Pressure (PSI)
O
utlet P
ressur
e
(PSI
)
Chart 2 (Lever Type)
Chart 1 (Screw Type)
There are a few items to remember concerning the proportioning valve:
• Standard Proportioning Valves (P/N 90-1000 & 90-2000)
AN-3 port with 3/8"-24 threads. Fittings (supplied): AN-3 male to AN-3 male
(P/N 73-820); AN-3 male to 3/16" inverted flare (P/N TE2089-188).
• Metric Proportioning Valve (P/N 90-1003 & 90-2003)
Threads: M10 x 1.0-6H with 74º included angle at base. No fittings supplied.
• Lever-type portioning valves:
A typical setup has the valve oriented in such a way that when the handle
is pushed towards the front of the vehicle it reduces the rear brake pres-
sure. When the handle is moved toward the rear of the vehicle it increases
the rear brake pressure. Handle can be re-oriented by loosening the jam
nut and rotating the handle. To determine which direction to move the
handle, refer to Chart 2 and Diagram 4.
• Screw-type portioning valves:
Rotating the adjustment knob in a clockwise direction will allow more
brake pressure to be applied to the rear brakes, counter-clockwise will
reduce the pressure (when installed on the rear calipers line).
• At higher pressures, a piston separates the fluid at the inlet and outlet
sides. No fluid flows through the valve. Therefore, you cannot bleed the
system at high pressure. Use light pedal pressure, and as an extra precau-
tion, move the lever to Position 7 (lever-type), or rotate adjusting knob in a
clockwise direction (screw-type), to reduce internal pressure.
• The proportioning valve can be used to reduce brake line pressure, but will
not increase it.
• Hooking it up backwards will not work.
• It can be used very effectively with a balance bar. Set the lever to Position 7
(lever-type) or set adjustment knob to the fully clockwise position (screw-
type). Adjust the balance bar until the rear brakes lock on the track with
slightly less pedal effort than the front brakes. The proportioning valve
is connected to the rear brakes in this case. Then, adjust the valve one
position at a time (lever-type) or rotate the knob counter-clockwise (screw-
type) until the proper balance is achieved.
• The proportioning valve is ideal for cars that must retain the stock calipers
and master cylinder, yet have too much rear brake when running soft tires.
A prime example is SCCA A Sedan (AS).
Brake Proportioning Valve
INSTALLATION INSTRUCTIONS
98
-12
61