Our training program will teach you all about how brakes work and the
correct methods of undertaking repairs of brakes. The ABS training manual,
designed by Wingate, is suitable for the professional as well as the DIY
mechanic. We also have a Counterman Training Manual for spares shops which
shows how to sell brake parts. Fill out the enquiry
form for more details.
Watch this website for excerpts of our manuals with hints. You can also
enquire about our Nu-Tech training sales video by completing the
enquiry form.
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Machine discs using the slowest feed rate with minimal depth to prevent grooving. For final clean-up use a solvent such as the spray-on ABS "brake cleaner". Do not use an oil based solvent. |
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Machining may leave a fine film of graphite on the surface that could affect breaking. Use the spray-on ABS "brake cleaner". Never use petrol for cleaning! |
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After fitting, once again wipe down the disc with a clean rag and the spray-on ABS "brake cleaner". |
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Bedding-in is always advisable to condition material surfaces correctly. At 60 kph apply brakes using light to moderate pedal effort reducing to 10 kph. Do this at least 10 times. |
Mechanical foot pressure converts to hydraulic pressure which forces against
the brake wheel cylinder rubbers, pushing the brake shoes in contact with the
brake drums. The brake shoe return spring retracts the shoes. Good brake
hardware is essential for good brakes.
Since most cars today have disc brakes, at least on the front wheels, they
need power brakes. Without this device, excessive power on the brake pedal
would be required. The central part in the power brake system is the brake
booster. The brake booster uses vacuum from the engine to multiply the force
that the brake pedal applies to the master cylinder.
The vacuum booster is a metal canister that contains a clever valve and a
diaphragm. A rod going through the center of the canister connects to the
master cylinder's piston on one side and to the pedal linkage on the other.
Another important part of the power brake system is the check valve.
This is a one-way valve that only allows air to be sucked out of the vacuum
booster. If the engine is turned off, or if a leak forms in a vacuum hose,
the check valve makes sure that air does not enter the vacuum booster. This
is important because the vacuum booster has to be able to provide enough boost
for a driver to make several stops in the event that the engine stops
running.
The vacuum booster is a very simple, elegant design. The device needs a vacuum source to operate. In gasoline-powered cars, the engine provides a vacuum suitable for the boosters. In fact, if you hook a hose to a certain part of an engine, you can suck some of the air out of the container, producing a partial vacuum. Because diesel engines don't produce a vacuum, diesel-powered vehicles must use a separate vacuum pump.
On cars with a vacuum booster, the brake pedal pushes a rod that passes
through the booster into the master cylinder, actuating the master-cylinder
piston. The engine creates a partial vacuum inside the vacuum booster on both
sides of the diaphragm. When you hit the brake pedal, the rod cracks open a
valve, allowing air to enter the booster on one side of the diaphragm while
sealing off the vacuum. This increases pressure on that side of the diaphragm
so that it helps to push the rod, which in turn pushes the piston in the
master cylinder.
As the brake pedal is released, the valve seals off the outside air supply While reopening the vacuum valve. This restores vacuum to both sides of the diaphragm, allowing everything to return to its original position.
Rack-and-pinion steering is quickly becoming the most common type of
steering on cars, small trucks and SUVs. It is actually a pretty simple
mechanism. A rack-and-pinion gearset is enclosed in a metal tube, with each
end of the rack protruding from the tube. A rod, called a tie rod, connects
to each end of the rack.
The pinion gear is attached to the steering shaft. When you turn the steering
wheel, the gear spins, moving the rack. The tie rod at each end of the rack
connects to the steering arm on the spindle.
The same principle basically applies to other steering mechanisms, such
as the Worm And Peg system or the Recirculating Ball system (see below).
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| Worm and peg steering gear | Recirculating-ball steering |
Power steering really means power assisted steering. Every time you turn the steering wheel, most of the hard work is done for you automatically by a sophisticated hydraulic mechanism incorporating a pump, drive belts, bearings, valves, hoses and seals.
The hydraulic power for the steering is provided by a pump that's driven by
the car's engine via a belt and pulley. The pump pulls hydraulic fluid from
the return line at low pressure and force it into the outlet at high pressure.
The amount of flow provided by the pump depends on the car's engine speed. The
pump must be designed to provide adequate flow when the engine is idling. As
a result, the pump moves much more fluid than necessary when the engine is
running at faster speeds. The pump contains a pressure-relief valve to make
sure that the pressure does not get too high, especially at high engine speeds
when so much fluid is being pumped.
The power-steering system should assist the driver only when he is exerting
force on the steering wheel (such as when starting a turn). When the driver
is not exerting force (such as when driving in a straight line), the system
shouldn't provide any assist. The device that senses the force on the
steering wheel is the rotary valve.
The key to the rotary valve is a torsion bar, a thin rod that twists when
torque is applied to it. The top of the bar is connected to the steering
wheel, and the bottom of the bar is connected to the pinion or worm gear
(which turns the wheels), so the amount of torque in the torsion bar is
equal to the amount of torque the driver is using to turn the wheels. The
more torque the driver uses to turn the wheels, the more the bar twists.
The input from the steering shaft forms the inner part of a spool-valve
assembly. It also connects to the top end of the torsion bar. The bottom of
the torsion bar connects to the outer part of the spool valve. The torsion
bar also turns the output of the steering gear, connecting to either the
pinion gear or the worm gear depending on which type of steering the car has.
As the bar twists, it rotates the inside of the spool valve relative to the
outside. Since the inner part of the spool valve is also connected to the
steering shaft (and therefore to the steering wheel), the amount of rotation
between the inner and outer parts of the spool valve depends on how much
torque the driver applies to the steering wheel.
When the steering wheel is not being turned, both hydraulic lines provide the same amount of pressure to the steering gear. But if the spool valve is turned one way or the other, ports open up to provide high-pressure fluid to the appropriate line. The resulting hydraulic pressure differential assists the driver in turning the wheels into the desired direction.
As with any other part of your car, things can go wrong if the power
steering system is not properly maintained. This seven-point quick check
procedure will pick up many problems before they interfere with power
steering performance:
To check for exterior hose damage, look for the following:
As with all safety related components which are subject to high rates of wear, disc brake rotors have a maximum safe life. The maximum life of a disc brake rotor is achieved when it reaches what we call the minimum thickness.
Disc Brake Rotor Minimum Thickness (RMT) is the minimum safe working thickness of a rotor. When a disc brake rotor reaches RMT it must be replaced.
Choosing to ignore RMT is a safety risk. Continued use of disc brake rotors below RMT can lead to brake system failure.
RMT is determined by the motor vehicle manufacturer during initial vehicle design. Some of the items which are considered when determining RMT are: Heat Absorption & Dissipation A brake system function is to take kinetic energy and transfer it into heat energy. This energy is created by the driver when he puts his foot on the brake pedal. Driver foot force is boosted , then converted into hydraulic pressure which forces the piston to move inside the calliper. This piston movement forces brake pads in contact with the spinning rotor. Rubbing between brake pads and the brake rotor generates heat which is then dissipated by convection to the atmosphere.
As rotor thickness reduces, so does its ability to absorb and dissipate heat generated during braking. Once RMT has been reached, the rotors ability to absorb and dissipate heat is reduced to such an extent that a significant reduction n braking capacity can result. This can be evident in premature fade and increased stopping distance.
As disc rotor and pad thickness reduces, the calliper piston moves further out inside the calliper body. When RMT has been reached with fully worn pads the piston may lack enough support within the calliper bore. This can cause it to jam the bore causing brake drag or lock. Brake drag will lead to excessive heat build up and possible brake fluid vaporisation. This will lead to half system failure and increased stopping distance.
Fully worn brake pads and RMT can allow, in some calliper designs, for the pad backing plate to jam between the calliper anchor bracket and disc rotor. This will cause either brake drag or wheel lock up. Both concerns can result in the loss of vehicle stability.
It is possible, under certain conditions when brake pads are fully worn and RMT is reached, for the calliper piston to cease forming a hydraulic seal. This will cause leakage, hydraulic half system failure and increased stopping distance.
Wingate recommends that disc brake rotors are measured as part of every brake service and replaced as soon as they reach the specified "minimum thickness".
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