Truck Ramp Stops an Out-Of-Control Big Rig in CA

[HTSS_TR]

Originally Posted By: Drew99GT
Originally Posted By: JHZR2
What is the white plume? Is it sand/dust from the gravel, water from some water-filled barrels or the radiator releasing steam, or is it the brakes themselves?


I'd say it's the brakes being fried. From what I've read, if you have a heavy load and you overcome the ability of the engine/jake brakes to maintain a decent without riding the brakes and then you ride the brakes, it's pretty easy to cook them until their gone. Seen plenty of big rigs on Interstate 70 with smoking brakes in Colorado. On the steeper passes, semi trucks I believe have a 45 mph decent speed limit.

Originally Posted By: Blkstanger
First rule.Never ride your brakes! EVER!
The best way to brake while going down a grade is stab braking. Say you want to travel down the grade at 45mph. Your truck gains speed up to 50mph. You get on the brakes hard and slow yourself to 35mph. Then stay off of them and let the truck slowly gain speed up to say 45-50mph until you brake again. This allows the brakes to cool between slowing events. I drive a lot of mountains and have never had a brake problem using this method.

Agreed. Riding the brake down hill is the wors thing a driver can do to his/her brake system.

On that Grapevine section of highway I-5 I only stab the brake every 1/2 miles or so, that way the brake is cool while coasting down steep hill. Same stab braking on Cajon pass of highway I-15 to Vegas.

 

[Silk]

We don't have them here...and we don't seem to have runaway trucks either. I'm sure they'll invent them soon and they will be everywhere.

When we were kids in the '60's, my brother and I often spent our holidays in the trucks of the company our father worked for. They went south of Auckland for coal and sand, and getting in and out of Auckland meant going over the Bombay Deviation, or ''The Divi'', just a bump in the road now, but a major obstical for a long time. Heading down to Kopuku for coal in a Leyland Comet, the driver yelled to us - ''I only get one shot at the brakes down here, so I only use them on the last corner!'' We went flying seemingly out of control down the hill, untill we got to the last corner when he braked hard and we got around. There isn't even a last corner there now.

 

[spackard]

snub braking
http://www.crashforensics.com/papers.cfm?PaperID=36
[ Reprinted from the Trucker's World Magazine, Volume 5, Issue 6, June 2001]

Snub braking is now the recommended method of downhill braking. This method works by: first, choosing the correct gear for the hill; second, allowing the truck to speed up to the maximum safe speed as it descends the hill; third, applying the brakes hard to slow the truck down 5 mph; and then repeating this process to the bottom of the hill.
...
However, to understand why snub braking is the recommended practice, you must also understand the basics of pneumatic balance. Trucks have relay valves to control the application and release of the air brakes. A standard truck-trailer usually has one relay valve for the tractor drive axles and one for the trailer axles. The relay valves are controlled by air pressure from the foot valve (brake pedal). This control pressure opens the relay valve allowing the desired amount of air pressure from the air tanks to pass through the valve and supply pressure to the brakes. Pneumatic balance is created by having equal air pressure at all wheel ends. Pneumatic imbalance is a result of these valves that open at different pressures. For example, a tractor may be setup with a relay valve that opens at 15psi (15psi crack pressure relay valve) and the trailer being towed may have a relay valve with a 3psi crack pressure. A vehicle setup this way would only apply the trailer brakes during controlled brake application, which typically has an application pressure of less than 10psi. However, a .snub. brake application of 20 to 30psi will open all valves and apply all brakes. This type of imbalance can also be a result of contaminants and alcohol in the air system that can cause these valves to hang-up and have higher than normal crack pressures.

Snub braking became the recommended method of downhill braking as a result of testing done by University of Michigan Transportation Research Institute. This research found that trucks with properly balanced brake systems had basically the same average brake temperature when using either the controlled or snub braking method. However, trucks with poor brake balance were found to have more uniform brake temperatures when the snub method was used. Unless pneumatic testing is performed on a truck to ensure that proper brake balance is maintained, there is no way to know if a truck has good brake balance. This type of testing is difficult to perform in most trucking operations since a tractor is usually hooked to several trailers over relatively short time periods. Therefore, for the purposes of deciding which braking method to use, it would be virtually impossible to determine if a truck has good brake balance. This is why snub braking is the recommended method.

 

[HTSS_TR]

Originally Posted By: Blkstanger
First rule.Never ride your brakes! EVER!
The best way to brake while going down a grade is stab braking. Say you want to travel down the grade at 45mph. Your truck gains speed up to 50mph. You get on the brakes hard and slow yourself to 35mph. Then stay off of them and let the truck slowly gain speed up to say 45-50mph until you brake again. This allows the brakes to cool between slowing events. I drive a lot of mountains and have never had a brake problem using this method.

Went to Lake Elsinore yesterday for dinner. It was another nice drive on the Ortega Highway - CA State Hwy 74, it is a 2-way mountain road with 5-6 miles down hill before Lake Elsinore city.

On front was a car then a Jeep and several other vehicles, the car immediately on front and the jeep on front of it had brake lights on for about 80-90% of the 5-6 miles down hill. I stayed back about 100 feet or so, I just shifted down a gear and stabbed the brake for a second every once in a while when I got close to the car on front. Yes, the distance between my car and the car on front did increase to more than 100 feet once in a while, but that was okay with me.

It is very normal for drivers to ride their brakes when they are down hill to control their speed. It is much better to shift down a gear or two then riding the brake, but most drivers didn't know that.

 

[Rand]

Originally Posted By: HTSS_TR

It is very normal for drivers to ride their brakes when they are down hill to control their speed. It is much better to shift down a gear or two then riding the brake, but most drivers didn't know that.


How do you shift down a couple gears when you have a cvt?
I know the engine braking on the CVT forester is very anemic.

I usually crank my A/C to max in the car and will go down a few gears upto 4000rpm.
and get decent engine braking.

Just shifting down doesn't do very much with the much lower friction engines of today.

I would say the A/C gives me more drag than dropping a gear easily.

 

[BigD1]

My rig developed an air brake chamber leak on the tractor during a long descent down a mountain, and I was grossing about 78,000 pounds. The compressor just could not keep up with the leak. Fortunately, I was getting close to the bottom, and the bottom of the mountain was mostly straight, so I bypassed the last truck ramp, and then let it roll to get my air pressure back up. No troopers were at the bottom that day. If there had been, I would have gotten a big fat ticket, and maybe a ride to jail.

 

[HTSS_TR]

Originally Posted By: Rand
Originally Posted By: HTSS_TR

It is very normal for drivers to ride their brakes when they are down hill to control their speed. It is much better to shift down a gear or two then riding the brake, but most drivers didn't know that.

How do you shift down a couple gears when you have a cvt?
I know the engine braking on the CVT forester is very anemic.

I usually crank my A/C to max in the car and will go down a few gears upto 4000rpm.
and get decent engine braking.

Just shifting down doesn't do very much with the much lower friction engines of today.

I would say the A/C gives me more drag than dropping a gear easily.

I have no idea, I don't know if you can shift down a gear or of a CVT car. I didn't try to shift down a gear of my daughter's 2014 Accord LX with CVT.

There is almost no engine braking on the Accord with CVT, I think they designed it that way to save gas, to raise the city MPG.

The old E430 has decent engine braking with 5-speed transmission on D and a lot more on 4th or 3rd gear.

Honda S2000 is manual transmission, so shifting down a gear of two is standard, and it has very good engine braking, the speed is about constant with about 4-5 degree down grade, I only shift down to 5th when the down grade is more than 6 degree.

 

[Nick1994]

Originally Posted By: dishdude
Originally Posted By: HTSS_TR
Originally Posted By: dishdude
I was going to rag on you for posting another worthless clickbait news story, but that video is pretty cool.

I was on I-10 to Phoenix several times to visit my brother, there isn't any "runaway truck ramps" on either direction of I-10.


It's flat. Why would they install a runaway truck sandpile?

I was just gonna say that