Jump to content
Chapala.com Webboard

Are ther any requirements for inspection of large truck brakes?


Recommended Posts

I recall a couple of years ago, a large truck lost its brakes coming down the libramento and nearly went into the Walmart parking lot.

I have noticed sever stories of trucks losing their brakes recently.

I am wondering of there are any required inspections for large trucks.

I have a feeling that in Mexico, truck maintenance is not a priority, and I always try to not drive, especially on a downgrade, in front of a large truck.

 

Link to comment
Share on other sites

Large trucks need airbrakes to stop. Most of the testing drivers, if it exists at all, is that they understand how airbrakes operate. They require an air tank, which is topped up with a 12 volt compressor. Pretty weak. No air, no brakes. To lessen the draw on the air tank they most often use what are called "Jake Brakes". These use the high compression of a diesel engine to suck air, and they are effective. They do not lock the wheels and they make that very loud and annoying Blat like sound. The only roadside inspections I have seen here, involve someone using a wooden tire thumper to detect faulty tires. Tires are very expensive and some truckers run worn out tires to save money.

  • Confused 1
Link to comment
Share on other sites

16 minutes ago, CHILLIN said:

...they understand how airbrakes operate. They require an air tank, which is topped up with a 12 volt compressor. Pretty weak. No air, no brakes.

You don't seem to understand air-brakes either. Th e compressor is used to disengage the brakes with no air meaning they are locked down allowing no movement.

  • Thanks 1
Link to comment
Share on other sites

15 minutes ago, AngusMactavish said:

You don't seem to understand air-brakes either. Th e compressor is used to disengage the brakes with no air meaning they are locked down allowing no movement.

I will admit to that. So how do the airtanks get filled? I see a lot of nasty truck skid marks on the highway. I guess air brakes are easily locked? It is dangerous out there, that is for sure. Anybody planning a Mexican road trip, take a drive on the public highway between Chapala and Ocotlan, any time of the day. You might change your mind - and your underwear.

Link to comment
Share on other sites

The air does not disengage the brakes, it engages them.

Let Mr. Google help:

https://www.nphm.com/blog/truck-accident/understanding-air-brakes-work-commercial-motor-vehicle-cmv/

Quote

First, the air compressor pumps air into the air storage tanks, or reservoirs, that are stored beneath the truck. That air is then pumped through the air brake lines where it eventually reaches the air brake (pictured here). On most typical “S-Cam” brake systems, when you push the brake pedal on a commercial motor vehicle, air pressure pushes a rod out (see gold rod on back side of brake in photograph), moving the slack adjuster. The slack adjuster is used to essentially calibrate the brake system and ensure that the internal spring mechanism is working appropriately (aka the spring is not fully extended – which would not create the appropriate friction needed to slow the vehicle).

As shown in the photo below (taken at the Truck Driving Academy), air flows through the nozzle to the air brake chamber (the black/metal cylinder with gold rings around it), which then causes the spring to move the “S-cam.” The “S-cam” forces the brake shoe lining away from one another and presses them inside the brake drum. This creates the friction and pressure needed to slow the wheel down. Similarly, when you release your foot from depressing the brake pedal, the “S-cam” rotates back, causing the spring to pull those same brake shoes away from the brake drum eliminating the friction and slow-down effect.

 

Link to comment
Share on other sites

33 minutes ago, CHILLIN said:

. No air, no brakes.  "Jake brake They do not lock the wheels and they make that very loud and annoying Blat like sound. 

You don’t have a clue how a Jake brake or air brakes work...

After the driver starts the truck he has to wait a few minutes for the air tanks to fill so he can release the brakes.. No air the brakes won’t release..  if the air pressure drops while the truck is in motion the air  brakes come on...nothing the driver can do about it.. Have you ever seen a parking brake on a trailer. ?  “No” because the trailer needs air pressure supplied from the truck to release the brakes...

You do not use an engine brake or Jake brake as it’s commonly called in wet or slippery conditions.. because it is easy to lock the wheels... 

Link to comment
Share on other sites

As to your original question, I don't know how that is handled in Mexico.

 

The two major problems no three are:

1 The brakes wear and get out of adjustment. Most modern setups have what are called automatic slack adjusters. If  they don't have those then the trucker should know how to make the adjustment. I do and have.

2 A major air leak. There are gauges on the dash for that. A pre- trip inspection will tell you if you have a major leak with a test. Basically a 10lb drop without the compressor running over a certain time period with the brakes applied while parked will let you know.

A safety mechanism applies the brakes when there is no air or when the air goes below a certain pressure. A buzzer goes off to let you know its time to pull over or else!

3 Heat. It will decrease breaking effectiveness in all vehicles. If a trucker doesn't know how to brake in mountainous ares he will be in big trouble fast. Depending on the grade, if the grade of descent is over a certain amount a low speed and constant light pressure will keep the brakes cooler than letting the vehicle speed up and slowing it down repeatedly with high pressure applied to the brakes. A lower gear and a jake brake if equipped is  is also in order.

How do I know this? Well I started driving in Illinois where there are almost no real hills. Then I moved to California and missed that question on the test. Later driving down the "Grapevine" south of Bakersfield I was glad I had that understanding. 30 MPH speed limit down that grade with runaway truck sand traps.

As far as how the brakes work with the foot pedal see the above post from Mainecoons.

So if they would post the degree of grade on the Libro, require that the truckers know how to drive it, and know how to check brakes then we could breath a little easier with a big truck behind us. Sort of reminds me of "Dual" movie with Dennis Weaver. 🤓

 

 

  • Like 1
Link to comment
Share on other sites

30 minutes ago, Youngtimer said:

As to your original question, I don't know how that is handled in Mexico.

 

The two major problems no three are:

1 The brakes wear and get out of adjustment. Most modern setups have what are called automatic slack adjusters. If  they don't have those then the trucker should know how to make the adjustment. I do and have.

2 A major air leak. There are gauges on the dash for that. A pre- trip inspection will tell you if you have a major leak with a test. Basically a 10lb drop without the compressor running over a certain time period with the brakes applied while parked will let you know.

A safety mechanism applies the brakes when there is no air or when the air goes below a certain pressure. A buzzer goes off to let you know its time to pull over or else!

3 Heat. It will decrease breaking effectiveness in all vehicles. If a trucker doesn't know how to brake in mountainous ares he will be in big trouble fast. Depending on the grade, if the grade of descent is over a certain amount a low speed and constant light pressure will keep the brakes cooler than letting the vehicle speed up and slowing it down repeatedly with high pressure applied to the brakes. A lower gear and a jake brake if equipped is  is also in order.

How do I know this? Well I started driving in Illinois where there are almost no real hills. Then I moved to California and missed that question on the test. Later driving down the "Grapevine" south of Bakersfield I was glad I had that understanding. 30 MPH speed limit down that grade with runaway truck sand traps.

As far as how the brakes work with the foot pedal see the above post from Mainecoons.

So if they would post the degree of grade on the Libro, require that the truckers know how to drive it, and know how to check brakes then we could breath a little easier with a big truck behind us. Sort of reminds me of "Dual" movie with Dennis Weaver. 🤓

 

 

To keep the brakes from over heating, truckers every where  are taught to use the engine to brake. A compression release brake, also commonly known as a “jake brake,” opens the exhaust valves at the top of the compression stroke, creating a loud noise similar to the firing of a gun. ... Engine braking is prohibited in some areas because of the loud noise it creates. So for the gringos complaining about the noise (noise existed when they bought near the hill) the truck incurs a higher risk of overheating it's brakes. As the brakes heat up they become less and less effective. 

  • Like 1
Link to comment
Share on other sites

6 hours ago, ea93105 said:

"Inspections ??...we don't need no stinkey inspections"

Treasure of Sierra Madre. Bogart.

To me when I read a truck "lost its brakes," I think of a line disconnecting causing a total and immediate loss of any braking ability. I don't even know if large rigs have emergency brakes.

I believe it is most likely human error of improper inspection and maintenance.

Who knows in Mexico?

Link to comment
Share on other sites

13 hours ago, geeser said:

To keep the brakes from over heating, truckers every where  are taught to use the engine to brake. A compression release brake, also commonly known as a “jake brake,” opens the exhaust valves at the top of the compression stroke, creating a loud noise similar to the firing of a gun. ... Engine braking is prohibited in some areas because of the loud noise it creates. So for the gringos complaining about the noise (noise existed when they bought near the hill) the truck incurs a higher risk of overheating it's brakes. As the brakes heat up they become less and less effective. 

 

A jake brake is there to assist but it is no replacement for brakes on a long down grade with 80,000 lbs or more behind you.

I know you didn't say it was a replacement but without proper braking even with the "Jake" on the brakes can overheat.

I know this from one million miles experience. That is actually low miles for a trucker, I only drove for 10 years.

 

 

Link to comment
Share on other sites

Wow! Thank you for the education on the braking system of the big rigs.

So what is the best way to avoid these loss of brake incidents? Maybe new drivers who have not been trained properly?

 

Link to comment
Share on other sites

22 hours ago, CHILLIN said:

Large trucks need airbrakes to stop. Most of the testing drivers, if it exists at all, is that they understand how airbrakes operate. They require an air tank, which is topped up with a 12 volt compressor. Pretty weak. No air, no brakes. To lessen the draw on the air tank they most often use what are called "Jake Brakes". These use the high compression of a diesel engine to suck air, and they are effective. They do not lock the wheels and they make that very loud and annoying Blat like sound. The only roadside inspections I have seen here, involve someone using a wooden tire thumper to detect faulty tires. Tires are very expensive and some truckers run worn out tires to save money.

On a semi the trailer brakes work differently.  Air keeps the brakes OFF so if you lose air the trailer wheels will lock up. In very cold climates sometimes the water will freeze in the air lines and the brakes of course will go on in the trailer with interesting consequences. 

 Jake brakes can be muffled or not muffled I believe.  Really steep hill applications  they use hydraulic retarders which have a radiator to cool the fluid used to retard the vehicle going downhill. Mining trucks or buses used on real steep hills have this type of system not normal trucks.

All the old low pressure air brake farm trucks I drove had an engine driven air compressor.  You only had a few pushes on the brakes before the pressure  went bye bye.  Air brakes don't have a normal pedal but use a gas pedal like design.  You never pump air brakes.  You normally have to get an extra endorsement to drive a truck with air brakes because of this design. Modern high pressure air brakes are a very different creature.  To save weight on the front axle many semis in the old days did not have front brakes. I don't know but do front axles on modern trucks use disk brakes these days??  Ahh memories!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...