What a great video. Thank you for helping me to understand how they work. This video should be shown to all new bus drivers to help them to understand the workings of the system. Thanks!
We're glad to share this kind of info. All thanks to Jefferson County. Since our video service is relatively new, what kinds of videos would you like to see in the future?
IF you lose Hydraulic pressure, you lose braking. you don't kow it until you push on brake pedal then you realize you don't have brakes. With Air brakes they won't allow the vehicle to be moved unless the system is working and you have air. once in motion if you lose air pressure below a designated range(usually 60 psi) the spring brake pops out and forces the brakes on and you cant stop it....this brings the vehicle to a stop .. and cant be moved until the air pressure is working.
@@devinevisionary You need air to *release* the brakes. Without air the brakes are engaged. You’ll never lose brakes with Air Brakes. With hydraulic brakes you need pressure to *engage* the brakes. If you lose pressure, no brakes. Air brakes much safer.
Because the only thing keeping the spring brake back is air. You lose air, and the truck sets the spring brake. A big and heavy truck needs to be able to stop even if you don't have air. With hydraulic breaks, you have a leak, you're fudged. Safety
Been watching these for the same reason. I'll be traveling with my family in our Skoolie, and I certainly want to be a safe operator. Good luck to you!
I had a sub bus driver once who really needs to see this. When a light changed to yellow she slammed the brakes but seemingly changed her mind about 4 times, pressing the pedal repeatedly until eventually deciding to stop.
That feathering technique was probably intentional. When you break that way, you create a very smooth, gentle stop. If a person was drinking a cup of coffee, they would not spill a drop when she’s driving/stopping.
@hondarider100r The brake booster has 2 separate halves. The rear section (Parking/emergency brakes) has spring force holding the brakes on and requires air from a spring brake valve to work against this spring to release the brakes. The front section (service/foot brakes) works in reverse and requires air to apply the brakes. This was not shown in this video. This air for the service brakes comes from your foot valve by driver demand. I hope this helps.
Very interesting video. Thanks for uploading it. I had no idea that air brake equipped vehicles have 80 percent of their braking power in the rear, which is the opposite of regular cars and trucks. I guess that makes sense though, given the increased number of tires (and axles, depending on the vehicle) back there. You could definitely see the size difference when he compared the front brake chambers to the previously shown rear chambers.
+crazyfvck The reason is because Service Brakes ( front ) and Spring Brakes ( rear ) are 2 different systems that back up one another. If The System gets a leak and all air drains, the rear brakes apply while the front brakes become useless, just as if the rear brakes lines don't allow the air to drain, you have full front breaks . you would want the rear brakes to suddenly lock up instead of the front so you can still manouver if there ever was an emergency, although, there is no such thing as " Emergency Brakes " Its called a Parking Break or " Maxies " it says it right on the knob the guy pulls. This video is full of errors.
While I understand your line of thinking that slowing down pushes the weight onto the front axle like a person slowing down from a sprint pushes weight onto the front foot it gets more complicated. Note that steer axles have only one wheel and will have a brake shoe with less width as opposed to drive/trailer axles. On tractors with semi trailers at least the major load is on the trailer tandems and drive axles and these have the most weight on them and the most traction so they do the most.
@hondarider100r The rod is cut in half. So when the spring is pushing down the rod, the half of the service brakes is pushed down as well. But when the half of the parking brake is pulled back by air pressure (in the rear chamber), applying the footbrake will pressurize the front chamber en push down the front part of the rod. The back half of the rod stays in place because the front half cannot pull on it due to the cut.
On the 30/30 piggyback the back spring side of the can takes about 60psi to release , and 60psi equivalent is all the apply braking you get when you have an emergency air loss . The sr1 or sr7 inversion valve modulates spring air pressure to give you a partial controlled brake application when you loose primary air .
Im thinking about buying a skoolie to turn into an RV. I'm order drive it in my state my need my air brake endorsement. This was informative and a lot easier to follow than the diagram in the CDL handbook from the DMV lol
Love it! This is what I was looking for to show how the brakes work for my trainees. They are always asking how it works. I will tell them to look this up! Thanks
I really hope you don't use this video for training. There are too many many mistakes and mis-information and the apprentices these days have too much to unlearn as it is
@@Mr.Lawton534 start with everything by Bendix airbrake. That should give you a good idea of the reality of truck brakes in the real world. Then you can go looking for videos with good info, but be choosie. Bendix and other manufacturers have good information to use when looking for more. I don't look at many of these, most everything I know I've learned by doing over the last 40+ years.
It depends, maybe u heard the air dryer releasing moisture or the parking brake being apllied. If the second option is what u heard, the operator pulled a valve that released in one hit the air inside the parking brake chamber. Its loud because it has a really big spring inside. If the first option is what u heard, it was because the air dryer releases humidity from the system periodically. Greetings.
I think it was great video. I am already going through a school bus training class and this gave more details about the air breaks. The caption had a lot of mis-used words but you can figure it out when you listen to the speaker.
Almost .. you can lose all the air in the primary reservoir (rear brake tank) and the spring brake will not apply. The driver is notified via the buzzer and lights on the dash that a major system fault has occured (green gauge shows "0".. the SR 7,or R7 or other inversion valve on truck will allow modulated parking brake applications to get the vehcile off the road.. usually good for 4 hard applies before the air is gone and NOW the wheels lock up.
old man The spring brakes do not use air to apply only to release , the front chamber of the piggyback is what does the application . On a tractor the 3rd axle often doesn't have a piggyback , only the apply chamber , it looks like a larger version of the front can
This is a very inmformative video. Is there any way to get a copy of this for training school bus drivers. I am a driver trainer and a State Instructor for the State of Illinois.
Question I think You can check the front break adjustment manually by pulling on the push rod. While the buses wheels are chocked and the pressure is released or the front air break is empty. Can I manually check the rear air breaks? If so how? Does the emergency break need to be engaged to test the rear air breaks? Or do they need to be released? Seems like the procedure is opposite to testing the front air bteaks.
and if your emergency or "maxi" brakes come on your in for quite a quick stop as they dont come on slowly they actually come on quite quickly. this comes from the son of a truck driver whos been in an air loss situation a few times
So pressure is lost but the spring gets compressed... I don’t get it, the spring compresses which means it requires energy to do so, somebody explain please
Alot of times I do wish school buses were standard in air brakes. I know they are optional in either hydraulic brakes or air brakes. Transit and Intercity I know are standard in air brakes.
it's duty cycle specific.. but the easiest way.. slowly (I mean slowly) open the drain cok on the wet tank into a baby food jar ..if you get more than a tablespoon of contamination (water. oil emulsion) time to change your cartridge.. period.. this is the rule..
mr will 1985.. ive looked this video up because of a debate i had with a friend. when the brakes are applied, air is actually being evacuated from the brakes. causing them to apply. the parking brake removes all of the air from the brakes.. that is why you have to let a truck build air pressure before it will move. this video is wrong, unless it is realy old.
same system as a bus. only difference is you have glad hands that connect to the trailer. one is an emergency (red) line the other is a service (blue) line once you disengage the parking brakes air flows through the red line to the rear chamber to disengage the spring which rotates the s-cam and releases the brakes and when the service brakes are applied air flows through the service line to the chamber where the spring is compressed, slack adjuster is pushed forward and the s-cam is rotated to apply the brakes
I notice sometimes when a commercial vehicle is parked you can hear the sound of air releasing from the vehicle. Now days I learned that is from the air brakes. What is happening when the air brakes make a releasing sound when the vehicle is parked?
My question for the whole industry is how often does the desiccant in the air drier need to be replaced barring oil contamination from a compressor with broken seals.
Often I'll open the trailer drain cock and get the foul smelling emulsion, but I'm sure the drivers rarely if ever dump the air tanks especially on the trailers even though they're supposed to daily. One driver thought he had an air leak that needed to be fixed because the air tanks would leak down overnight lol. Certainly audible and perceivable air leaks in a short time period need to be fixed, but it's a pneumatic system not a refrigerant system. They think air driers are maintenance free.
Whoa Whoa at 5:47 he says "when the emergency brake is released" and the video shows the push rod going out that is wrong, going out would be applied not released!
that part of the video was particularly unclear if not completely wrong. they glossed over how normal service break application is made making it sound like it was some externality a rod connection of some kind. also some older passenger buses have dd3 brakes which have two air Chambers and a much smaller spring that serves a different purpose.
+Henry Chuong You're confusing Stopping Power with Breaking Power. Spring brakes ( rear ) are stonger than Service Brakes ( front ). This video isn't very accurate on the air brake system. If your going for your test, I would not memorise any of this, study your manual instead.
+MapleBalls The spring brakes in the rear are not stronger than the service brakes. The springbrake only takes about 60psi to release. You can apply the full 120psi to the service brakes.
+MapleBalls Both front and back brake chambers are service brakes. The rears have springbrakes in the piggyback for parking. In an emergency a straight truck or bus uses an sr1 valve to modulate the air in the spring chamber (loss of primary air circuit). Also I've never seen a single tank (even a partitioned tank) on a truck and that bus isn't any smaller than any 2 axle truck
Prior to the 70s heav trucks didn't even have front brakes, then they put very narrow shoes on with a very small air can, and a pressure limiting valve so that you only got 40% application. Now they are using a 7" shoe with a #24 can and 8 5/8s shoes on the rear in an attempt to reduce stopping distances and a big push for disc brakes. As long as the abs works you can't lock up the brakes and on a loaded truck you would have to almost put the foot pedal all the way to the floor
I like your video but giving bus drivers a false sense of security when you say the parking brake will pop out and stop the bus. You have to loose air from both tanks at the same time to make this happen. A duel air brake system with evenly disperse the air if the opposite tank has lost air. Other than that, I love your video very informative.
no as soon as you lose pressure your brakes do apply. rear brake chamber has air flowing all the time that's the parking brake/emergency brake as soon as that loses air spring decompresses which pulls the slack adjuster, rotates the S-Cam and applies the brakes. service brakes are the exact opposite when air is applied spring compresses pushing the slack adjuster which rotates the S-Cam and applies the brakes.
+Mitch S The spring does not apply perssure in Service brakes. The membrane fills with air & the pressure applies the brakes. Only Spring Brakes are applied with presure from the springs, hence the name.
I never said the spring applies the brakes I said air enters the spring compresses which applies the brakes aka the spring holds back the brakes and air pressure applies them. now that I read it yes it is confusing so I apologize but that's what I meant to say
+Dawn Thompson not to mention, if the spring brakes automatically apply, and you are going more than 5kph, the vehicle will stop...really quickly...and it will hurt...i had the springs come on in the yard at only 5 kph, and it hurt...any faster and it may break something.
jfsa380 if you have enough weight on the truck at speeds over 5mph it probably won't lock the brakes . remember you're only getting an equivalent brake application of about 60 psi not the 120 psi of a full brake application .
This video is sort of wrong. It takes air pressure to RELEASE the brakes. It’s a fail-safe so of you lose air pressure dramatically such as a sheared off air line or a stuck open moisture drier valve, you don’t lose brakes. In that circumstance, all brakes would automatically engage.
That’s true with smaller cars and some medium duty vehicles. However that’s not the case in heavy duty trucks with air brakes. The rear brakes are your primary and front are the secondary.
Nose dive effect. Some treadle valve on european truck has a predominance port . This will counter the nose dive effect, which will prevent jack knife effect on semi trucks
That animation on the spring brakes is way backwards!! The air pushes BACK the spring allowing the brakes to release and it is ....wait for it....the SPRING that returns the rod to the "applied" position should air pressure be lost. damn, way backwards lol
There are many errors in this video. Both Terminology and animation on the system are way off. Emergency Brake? No such thing. If anyone is going for their license, study your Provincial / State manuals, not this... you will fail.
What a great video. Thank you for helping me to understand how they work. This video should be shown to all new bus drivers to help them to understand the workings of the system.
Thanks!
A very informative video for truck driving students like myself! Thank you.
We're glad to share this kind of info. All thanks to Jefferson County. Since our video service is relatively new, what kinds of videos would you like to see in the future?
IF you lose Hydraulic pressure, you lose braking. you don't kow it until you push on brake pedal then you realize you don't have brakes.
With Air brakes they won't allow the vehicle to be moved unless the system is working and you have air. once in motion if you lose air pressure below a designated range(usually 60 psi) the spring brake pops out and forces the brakes on and you cant stop it....this brings the vehicle to a stop .. and cant be moved until the air pressure is working.
I get confused cuz why it don't keep rolling if breaks don't work ? Why does it stop ???
@@devinevisionary
You need air to *release* the brakes.
Without air the brakes are engaged.
You’ll never lose brakes with Air Brakes.
With hydraulic brakes you need pressure to *engage* the brakes.
If you lose pressure, no brakes.
Air brakes much safer.
@@craiglittle7367 I passed thank you 😊
@@devinevisionary
Congratulations!
You’re going to drive school bus?
Because the only thing keeping the spring brake back is air. You lose air, and the truck sets the spring brake. A big and heavy truck needs to be able to stop even if you don't have air. With hydraulic breaks, you have a leak, you're fudged. Safety
Very informative. It's an excellent way to get acquainted with the important parts of using air breaks when I get my Skoolie.
Been watching these for the same reason. I'll be traveling with my family in our Skoolie, and I certainly want to be a safe operator. Good luck to you!
I love the air brake release sound of the bus on this video!
+Ben Sommer If you want to hear it, go to 7:47 in the video!
+Ben Sommer You can also download the "New Air Brake Release Sound Mix 2016" in the iTunes store for only $1.99 US. :-)
Love it. I can't stop picturing it in my head.
Yeah something that my school bus trainees understand cut in and cut out along with spring brakes. Thank you !
I had a sub bus driver once who really needs to see this. When a light changed to yellow she slammed the brakes but seemingly changed her mind about 4 times, pressing the pedal repeatedly until eventually deciding to stop.
That feathering technique was probably intentional. When you break that way, you create a very smooth, gentle stop. If a person was drinking a cup of coffee, they would not spill a drop when she’s driving/stopping.
THANKS! TRULY MOTIVATIONAL VIDEO, SO MUCH TO LEARN FROM THE COMPRESSED AIR BRAKE SYSTEM.
Great source of information, LOVE IT!!!!
Thanks, just what I was looking for! You will part of my success when I pass my air brakes test for school bus.
Thank you for keeping this video up. Very helpful and easy to understand.
EXCELLENT demo!!
@hondarider100r The brake booster has 2 separate halves. The rear section (Parking/emergency brakes) has spring force holding the brakes on and requires air from a spring brake valve to work against this spring to release the brakes. The front section (service/foot brakes) works in reverse and requires air to apply the brakes. This was not shown in this video. This air for the service brakes comes from your foot valve by driver demand. I hope this helps.
Very interesting video. Thanks for uploading it. I had no idea that air brake equipped vehicles have 80 percent of their braking power in the rear, which is the opposite of regular cars and trucks. I guess that makes sense though, given the increased number of tires (and axles, depending on the vehicle) back there. You could definitely see the size difference when he compared the front brake chambers to the previously shown rear chambers.
+crazyfvck The reason is because Service Brakes ( front ) and Spring Brakes ( rear ) are 2 different systems that back up one another. If The System gets a leak and all air drains, the rear brakes apply while the front brakes become useless, just as if the rear brakes lines don't allow the air to drain, you have full front breaks . you would want the rear brakes to suddenly lock up instead of the front so you can still manouver if there ever was an emergency, although, there is no such thing as " Emergency Brakes " Its called a Parking Break or " Maxies " it says it right on the knob the guy pulls. This video is full of errors.
Thank you for having this video on air brakes its a good pastime .:)
Thank you for your knowledge sharing ...it's very helpful to understand ❤👍
While I understand your line of thinking that slowing down pushes the weight onto the front axle like a person slowing down from a sprint pushes weight onto the front foot it gets more complicated. Note that steer axles have only one wheel and will have a brake shoe with less width as opposed to drive/trailer axles. On tractors with semi trailers at least the major load is on the trailer tandems and drive axles and these have the most weight on them and the most traction so they do the most.
Thanks, great info nicely presented ; - )
very informative videos!!! tnks a lot!!!!
@hondarider100r
The rod is cut in half. So when the spring is pushing down the rod, the half of the service brakes is pushed down as well. But when the half of the parking brake is pulled back by air pressure (in the rear chamber), applying the footbrake will pressurize the front chamber en push down the front part of the rod. The back half of the rod stays in place because the front half cannot pull on it due to the cut.
On the 30/30 piggyback the back spring side of the can takes about 60psi to release , and 60psi equivalent is all the apply braking you get when you have an emergency air loss .
The sr1 or sr7 inversion valve modulates spring air pressure to give you a partial controlled brake application when you loose primary air .
Or install a cage bolt in each piggyback
Great video thanks
Thank you so very much for your videos
good job..thank you sharing your Video..im watching from DIPOLOG CITY,ZAMBOANGA DEL NORTE, PHILIPPINES
Really great video 👍
Im thinking about buying a skoolie to turn into an RV. I'm order drive it in my state my need my air brake endorsement. This was informative and a lot easier to follow than the diagram in the CDL handbook from the DMV lol
Love it! This is what I was looking for to show how the brakes work for my trainees. They are always asking how it works. I will tell them to look this up! Thanks
I really hope you don't use this video for training. There are too many many mistakes and mis-information and the apprentices these days have too much to unlearn as it is
@@cbmech2563 what videos you recommend?
@@Mr.Lawton534 start with everything by Bendix airbrake. That should give you a good idea of the reality of truck brakes in the real world. Then you can go looking for videos with good info, but be choosie. Bendix and other manufacturers have good information to use when looking for more. I don't look at many of these, most everything I know I've learned by doing over the last 40+ years.
@@cbmech2563 cool,thanks a lot amigo.
@@Mr.Lawton534 your welcome
Thanks every trucking company should play this video for new drivers .
And long time drivers like me I learned plenty about brakes I didn't know after 800 k miles driven .
driver's should learn this in CDL training for their pre-trip. if they don't then that place isn't teaching people right
nisw1918 and school districts.
ok how does the pressure from braking move the rod back out if there is already pressure in the chamber keeping the spring from moving ??
excellent info I love it
It depends, maybe u heard the air dryer releasing moisture or the parking brake being apllied. If the second option is what u heard, the operator pulled a valve that released in one hit the air inside the parking brake chamber. Its loud because it has a really big spring inside. If the first option is what u heard, it was because the air dryer releases humidity from the system periodically. Greetings.
I think it was great video. I am already going through a school bus training class and this gave more details about the air breaks. The caption had a lot of mis-used words but you can figure it out when you listen to the speaker.
Because:
-oil leak -> no brakes
-air leak -> brakes lock up
Air brakes are also more powerful.
agreed, saw that error right away!
He meant to say when brake is APPLIED!
will look into this and see if we have a video for you. thanks for watching.
Almost .. you can lose all the air in the primary reservoir (rear brake tank) and the spring brake will not apply. The driver is notified via the buzzer and lights on the dash that a major system fault has occured (green gauge shows "0".. the SR 7,or R7 or other inversion valve on truck will allow modulated parking brake applications to get the vehcile off the road.. usually good for 4 hard applies before the air is gone and NOW the wheels lock up.
Thank you.
Thanks, I'm purchasing a mil surplus trailer that has airbrakes. Pretty easy, only recommendation is make sure tires are blocked
wow!! i learned sooo much!!
Thanks for update this vedio it's easily understood
Air rushes through relays?
THANK YOU FOR THIS VIDEO
old man
The spring brakes do not use air to apply only to release , the front chamber of the piggyback is what does the application . On a tractor the 3rd axle often doesn't have a piggyback , only the apply chamber , it looks like a larger version of the front can
Cbmech zasddffghjjklwertylkj
Ok?
The Tool Guy .nj
This is a very inmformative video. Is there any way to get a copy of this for training school bus drivers. I am a driver trainer and a State Instructor for the State of Illinois.
thank you
Question
I think You can check the front break adjustment manually by pulling on the push rod. While the buses wheels are chocked and the pressure is released or the front air break is empty.
Can I manually check the rear air breaks? If so how?
Does the emergency break need to be engaged to test the rear air breaks? Or do they need to be released?
Seems like the procedure is opposite to testing the front air bteaks.
Thank You.
ri1ch guys dubai
Drum brakes still alive and well. 😀
Do you have a video for a complete pre-trip inspection suitable for use to train new drivers for their CDL Skills Test?
Would definitely want to see a video for pre trip.
this was very helpful
and if your emergency or "maxi" brakes come on your in for quite a quick stop as they dont come on slowly they actually come on quite quickly. this comes from the son of a truck driver whos been in an air loss situation a few times
you have a 1/4 inch in the shore to break drum so say it /what good is this with out measurement
She sounds like the air brake on a bus 😂😂😂
Thanks
So pressure is lost but the spring gets compressed... I don’t get it, the spring compresses which means it requires energy to do so, somebody explain please
Alot of times I do wish school buses were standard in air brakes. I know they are optional in either hydraulic brakes or air brakes. Transit and Intercity I know are standard in air brakes.
it's duty cycle specific.. but the easiest way.. slowly (I mean slowly) open the drain cok on the wet tank into a baby food jar ..if you get more than a tablespoon of contamination (water. oil emulsion) time to change your cartridge.. period.. this is the rule..
mr will 1985.. ive looked this video up because of a debate i had with a friend. when the brakes are applied, air is actually being evacuated from the brakes. causing them to apply. the parking brake removes all of the air from the brakes.. that is why you have to let a truck build air pressure before it will move. this video is wrong, unless it is realy old.
4:33 rear brake chamber, 5:39 S-cam/foundation brake, 6:01
I just had curiousity on how trucks brake, I've been playing Euro Truck 2 :D
same system as a bus. only difference is you have glad hands that connect to the trailer. one is an emergency (red) line the other is a service (blue) line once you disengage the parking brakes air flows through the red line to the rear chamber to disengage the spring which rotates the s-cam and releases the brakes and when the service brakes are applied air flows through the service line to the chamber where the spring is compressed, slack adjuster is pushed forward and the s-cam is rotated to apply the brakes
Roderick same xD
I notice sometimes when a commercial vehicle is parked you can hear the sound of air releasing from the vehicle. Now days I learned that is from the air brakes. What is happening when the air brakes make a releasing sound when the vehicle is parked?
MrWill1985 moisture is being released from the air dryer.
what he means is.. the more axles on the rear the more braking power there is... make sence!
if spring air brake booster diaphragm internal leakage what happened
My question for the whole industry is how often does the desiccant in the air drier need to be replaced barring oil contamination from a compressor with broken seals.
I don't know that there is an absolute recommendation but most of the companies I have dealt with replace it on an annual basis
Super
Often I'll open the trailer drain cock and get the foul smelling emulsion, but I'm sure the drivers rarely if ever dump the air tanks especially on the trailers even though they're supposed to daily. One driver thought he had an air leak that needed to be fixed because the air tanks would leak down overnight lol. Certainly audible and perceivable air leaks in a short time period need to be fixed, but it's a pneumatic system not a refrigerant system. They think air driers are maintenance free.
Whoa Whoa at 5:47 he says "when the emergency brake is released" and the video shows the push rod going out that is wrong, going out would be applied not released!
I noticed the same thing. Its definitely incorrect
that part of the video was particularly unclear if not completely wrong. they glossed over how normal service break application is made making it sound like it was some externality a rod connection of some kind. also some older passenger buses have dd3 brakes which have two air Chambers and a much smaller spring that serves a different purpose.
LOL "fireweed dr."
Tem o vídeo traduzido para portugues.
GREAT!!! Thanks I understand now!!:) I'm studying for my CDL
👍
Este video 5:15 muestra el funcionamiento per está al reves. Cuando le metes aire el vastago se mete y cuando le sacas el aire sale
Prob is 'nt,just need a gallon of the stuff for a big vehicle.Air cheap and constantly renewable,by compressor.
si estaria en español estaria a toda madre
이런.원리가.잇어네요
역시.틀리내요
Nutguy95, you are wrong, people need to stop providing incorrect information to people when they think they know. On buses 80% is in the rear.
he said the rear provides more braking power than the front (3:52)..but isn't most of the breaking power of any vehicle in the front?
+Henry Chuong You're confusing Stopping Power with Breaking Power. Spring brakes ( rear ) are stonger than Service Brakes ( front ). This video isn't very accurate on the air brake system. If your going for your test, I would not memorise any of this, study your manual instead.
+MapleBalls Thanks!
+MapleBalls
The spring brakes in the rear are not stronger than the service brakes. The springbrake only takes about 60psi to release. You can apply the full 120psi to the service brakes.
+MapleBalls
Both front and back brake chambers are service brakes. The rears have springbrakes in the piggyback for parking. In an emergency a straight truck or bus uses an sr1 valve to modulate the air in the spring chamber (loss of primary air circuit). Also I've never seen a single tank (even a partitioned tank) on a truck and that bus isn't any smaller than any 2 axle truck
Look up sr1 valves on CZcams
Why REAR brakes need 80% of the air? If its the front of the vehicle that has all the mass of it when the driver presses the pedal brake
Because the rear brakes do 80% of the braking. The front brake shoes and air can are much smaller, though this is changing on the newer vehicles.
@@cbmech2563 But if that were the case, wouldn't the rear wheels spin every time you hit the brake?
Prior to the 70s heav trucks didn't even have front brakes, then they put very narrow shoes on with a very small air can, and a pressure limiting valve so that you only got 40% application.
Now they are using a 7" shoe with a #24 can and 8 5/8s shoes on the rear in an attempt to reduce stopping distances and a big push for disc brakes. As long as the abs works you can't lock up the brakes and on a loaded truck you would have to almost put the foot pedal all the way to the floor
@@eliasrosales4899 I'm assuming you meant lock it up and slide the tires?
Go search for Jake brake.
I like your video but giving bus drivers a false sense of security when you say the parking brake will pop out and stop the bus. You have to loose air from both tanks at the same time to make this happen. A duel air brake system with evenly disperse the air if the opposite tank has lost air. Other than that, I love your video very informative.
no as soon as you lose pressure your brakes do apply. rear brake chamber has air flowing all the time that's the parking brake/emergency brake as soon as that loses air spring decompresses which pulls the slack adjuster, rotates the S-Cam and applies the brakes. service brakes are the exact opposite when air is applied spring compresses pushing the slack adjuster which rotates the S-Cam and applies the brakes.
+Mitch S The spring does not apply perssure in Service brakes. The membrane fills with air & the pressure applies the brakes. Only Spring Brakes are applied with presure from the springs, hence the name.
I never said the spring applies the brakes I said air enters the spring compresses which applies the brakes aka the spring holds back the brakes and air pressure applies them. now that I read it yes it is confusing so I apologize but that's what I meant to say
+Dawn Thompson not to mention, if the spring brakes automatically apply, and you are going more than 5kph, the vehicle will stop...really quickly...and it will hurt...i had the springs come on in the yard at only 5 kph, and it hurt...any faster and it may break something.
jfsa380 if you have enough weight on the truck at speeds over 5mph it probably won't lock the brakes . remember you're only getting an equivalent brake application of about 60 psi not the 120 psi of a full brake application .
80 precent of breaking power from the rear?? That seems backwards
Yup. If you have more braking up front, the rear of the truck lifts up. More braking in rear, the truck stays planted to the ground.
This video is sort of wrong. It takes air pressure to RELEASE the brakes. It’s a fail-safe so of you lose air pressure dramatically such as a sheared off air line or a stuck open moisture drier valve, you don’t lose brakes. In that circumstance, all brakes would automatically engage.
How about planes they are more powrful
4:42 2,500 lbs not 25,000 lbs.
3:52 Thats incorrect! The FRONT brakes provide about 80% of the braking power not the rear! its the same with almost every road vehicle.
you are NOT going to get more braking force out of the front brake (5 inch shoes type 20 or 24 can )than out of the rear (7inch shoes type 30 can)
That’s true with smaller cars and some medium duty vehicles. However that’s not the case in heavy duty trucks with air brakes. The rear brakes are your primary and front are the secondary.
Nose dive effect. Some treadle valve on european truck has a predominance port . This will counter the nose dive effect, which will prevent jack knife effect on semi trucks
no entendí mucho
That animation on the spring brakes is way backwards!!
The air pushes BACK the spring allowing the brakes to release and it is ....wait for it....the SPRING that returns the rod to the "applied" position should air pressure be lost. damn, way backwards lol
There are many errors in this video. Both Terminology and animation on the system are way off. Emergency Brake? No such thing. If anyone is going for their license, study your Provincial / State manuals, not this... you will fail.
MapleBalls In the US we commonly call a Parking Brake an Emergency Brake, so it is not incorrect to call it that no matter what vehicle you’re in.
Lewis Johnson, Thank you for explanation. I APPRECIATE IT.
Yea, its wrong. i guess a confussion after talking so much of release-apply, release-apply.
Why the fuck was this in my recommended.
Fix yo brakes