A look at the movements and states of operation of the air brake relay.
Relays are fitted to an air braking system for larger vehicles to speed up the application and release of the brakes, minimising brake lag, which is the time it takes between the driver operating the controls (park brake/foot brake valve) and the action actually happening at the brakes.
For a bit more background before watching this video, take a look at our “introduction to air brakes”
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Another Way by Psykick (c) 2016 Licensed under a Creative Commons Attribution (3.0) license.
The air dryer filters moisture and other contaminants from the compressed air in the air brake system – watch the video! SUBSCRIBE TODAY! ► Get 30% OFF Air Brake Course. Coupon “youtube30” CLICK THE LINK SEE TOPICS BELOW.
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Older Air Brake Systems 1:25
Pre trip Inspection 3:30
Draining the Wet Tank 4:20
ADIS Systems (Air Dryer Integrated System) 6:18
Question – Where is the Air Dryer located on your vehicle? 11:04
Most drivers’ manuals indicate that the air dryer is optional; however, this air brake components have been an integral part of a truck or bus’ air brake system for more than a quarter century.
The air brake system’s air dryer is located between the compressor and the first air tank. On older systems it is located between the compressor and the “wet” (supply) tank. On newer ADIS (Air Dryer Integrated Systems) the air dryer is located between the compressor and the primary and secondary air tanks (reservoirs).
There are two indicators of ADIS systems:
1) The governor is located within close physical proximity to the air dryer – often right beside the air dryer;
2) When building air pressure, an ADIS system will build either the secondary or primary sub-system to approximately 100 psi (pounds per square inch) and then build the other system.
When both systems attain approximately 100psi, both systems will build to maximum system pressure. When the air brake system attains maximum pressure the air dryer will purge, discharge or spit. The air dryer is the first indicator that the air brake system is at maximum pressure. Yet, when conducting a pre-trip inspection, a driver must confirm by the air gauges on the dash that yes, in fact, the system is at maximum pressure.
Learn how to inspect tires for a CDL pre-trip inspection test. Watch the video!! SUBSCRIBE TODAY! ► Get 30% OFF Pre-Trip Inspection Course. Coupon “youtube30″ CLICK THE LINK
For the purposes of the pre-trip inspection, tires are a major component. Learn how to inspect tires to be successful on your road test.
Inspecting a Tire for a CDL Road Test
Now you need to know for the purposes of a road test that tread depth on the front is 3mm (1/8 inch OR 4/32 in NY and other states) minimum to pass the road test or to pass and MVI (Motor Vehicle Inspection) that the tread depths.
On the rear tires it can be 1/16 inch OR 2/32” in NY and other states or 1.6mm.
The other criteria that a tire has to have to pass a road test – it cannot have any cuts or gashes in the tire that are longer than 2.5cm or one inch, and there cannot be cuts or abrasions in the tire that expose the chord inside the tires.
If any of those criteria exist, the tire won’t pass, will not pass an MVI, you will not pass a road test, and if you show up with tires with those conditions for road test, you won’t be able to take the road test.
On the top of this tire—this is a front tire—on this truck you begin to see that this tire is beginning—there’s a dip here in the tread. This tread is worn deeper than this tread. And this side – so this tire has uneven wear – you can see that it’s worn more on this side of the tire than it is on this side of the tire. This front tire on this truck is not safe and needs to be replaced. Tires on the front of commercial vehicles have to be brand new.
Tire Wear Bars
After you pass your road test, you don’t really need to know the information that is required in terms of 1.6mm on the rear, 3mm on the front, and gashes that are not longer than 2.5cm. What you do need to know is inside the tread are wear bars. And you can see the wear bars here.
If the tire tread is down to wear bars on the steer tires on the front, the tire needs to be replaced. Now as I said, steer tires on the front of the trucks—commercial vehicles, buses those types of things—have to be new tires.
A new steer tire on the front of a commercial vehicle is $600 to a $1000, depending on the type of tire. This tire is not a very expensive tire, thus it’s abnormally worn on the front and will soon need to be replaced. So you either spend a little bit more and get a better quality tire and it’ll last longer.
Now the reason, because a front steer tire is $600—$1,000 – the reason they put recaps on the rears and on the trailers is because a recap will cost you about $375—$400. There’s considerable saving in getting recaps for the rear of semi trucks and the trailers. They’re also allowed on the rear of buses, but not on the steer axles. They have to be brand new. That’s a little bit of information about tires on commercial vehicles.
As well, other information about tires will help you to stay employed when you begin work as a commercial driver – bus or truck.
Finally, requirements for tires that will allow your vehicle to pass an inspection and not be put out of service by authorities if you are pulled into the scale house.
Good luck on your road test!