J-Brake Question

roshea · Jan 16, 2010

black_dog106 said: ↑

######......... it comes down to common sense..... If the engine brake is sliding the tires, turn it off......
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except in many cases by then it's too late.

Longhood379 · Jan 16, 2010

roshea said: ↑

Can't agree with you on that at all. To say there is NO CHANCE of your tires losing traction or brakes locking up is a pretty strong statement. NO means never, not physically possible, can't happen. A blanket statement covering all possible load conditions from bobtail to hauling triple trailers, unloaded to gross weight.

If your brakes are adjusted properly, which of course they are because you checked them, then a gentle application of braking to ALL wheel positions will allow a much lower braking force per wheel to be applied to achieve the same amount of speed reduction achieved by using an engine brake alone. Also you are in complete control of the amount of braking force. Engine brake is not controllable except for two or three individual levels. Engine brakes are capable of producing hundreds of horsepower in braking force roughly equivalent to the HP rating of the engine itself, so even divided by three at the lowest level it can be easy to break traction. Also tell me how you can apply an engine brake gently, and apply more or less pressure as needed as you begin to slow? Also you lose braking as speed is reduced and rpms drop.

Engine compressor converter "brakes" are variable and create no measurable wear to anything your explanation sounds like you have never operated one
An engine at 1000 rpm on lo setting will only absorb about 50 horse power if you have noticed the lever to the right or the seat you select drive ratios with that so your no control story makes no sense
When used by an experienced skilled operator they are more predictable than wheel brakes which can also do all kinds of things to get you in trouble. I believe that a tractor trailer should be driven in a manner that you shouldn't need the wheel brakes Because they don't always behave like they are supposed to especially in cold weather.

Those of you who might want to know the "jake" turns the engine into an air compressor braking is acheived because the energy required to compress the air on the up stroke is released at the top of the stroke, usually by a hydraulic bridge between the injector cam lobe and the exhaust valve . with the compression released in this manner the energy is released to atomsphere instead of pushing the piston back down.
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JustSonny · Jan 16, 2010

"This is going to sound like a stupid question, but when, exactly, do you use it?"

(part of a post by Dodgeram440rt)

Dodgeram, I appreciate the question very much! I've been compiling a "paper file" of useful threads and this one will definitely be in it. I love it when the old hands take the time to share their knowledge and experience. When I actually do get in school, then on the road, I feel I'll be way ahead of the game because of these guys!

roshea · Jan 16, 2010

Les2 said: ↑

I use my Jake's all the time. It doesn't cause excessive fuel usage, or excessive wear on the engine if used properly.

Anyone whos ever owned a truck without jakes and then owned one with jakes will tell you how much they love them and how much longer their brakes lasted.
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Oh yes, I will admit I love the jake and wouldn't be without it. Fuel usage is a matter of ANY unnecessary braking being a waste, when you need brake except for controlling speed downhill, you have used more energy (fuel) than needed to get to where you are. Yes, brakes will last longer, but there is a trade-off because tire wear will be excessive on the drive tires. Brake wear can be minimized by driving more efficiently all around. Something, somewhere, is going to have to stop the truck and it will come with a cost either way. If you let natural forces work for you instead it will impact your bottom line. I've consistently been in the 7-8mpg range for years because after safety my first consideration is fuel consumption. As an O/O I understand my two biggest operational expenses are fuel and tires. Driving habits affect the bottom line. Not withstanding safety, how any of us drive is our own individual preference, neither is right or wrong. Knowing your options is always a good thing.

Les2 · Jan 16, 2010

roshea said: ↑

Oh yes, I will admit I love the jake and wouldn't be without it. Fuel usage is a matter of ANY unnecessary braking being a waste, when you need brake except for controlling speed downhill, you have used more energy (fuel) than needed to get to where you are. Yes, brakes will last longer, but there is a trade-off because tire wear will be excessive on the drive tires. Brake wear can be minimized by driving more efficiently all around. Something, somewhere, is going to have to stop the truck and it will come with a cost either way. If you let natural forces work for you instead it will impact your bottom line. I've consistently been in the 7-8mpg range for years because after safety my first consideration is fuel consumption. As an O/O I understand my two biggest operational expenses are fuel and tires. Driving habits affect the bottom line. Not withstanding safety, how any of us drive is our own individual preference, neither is right or wrong. Knowing your options is always a good thing.
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OK, jake usage will not hurt your fuel mileage unless you're going down the road and for no good reason you're on and off the pedal. But, if you was to do this without a jake, you'd notice a difference in fuel mileage also.

Sorry, But I know this as fact. I had to suffer a week without my jakes. the only difference I noticed, was me kicking the trans into neutral. My MPG's never changed.

dodgeram440rt · Jan 16, 2010

I'm afraid I've started a war between the old hands here. I really appreciate all the responses and the opinions. Everyone has their own methods of driving and to say one is better than the other would be wrong. Obviously both methods work for their respective drivers.

I do have to say that all of the training and schooling I have been thru up to this point say that you should NOT use the engine brake in any kind of slick conditions. I don't know, that just seems like common sense to me. While I have not driven a big truck in the snow (yet), I have lived in snowy climates all my life so I know about winter driving. In this particular case, I have to agree with Roshea, that the braking power of 18 wheels would be far better than that of only 4. You have way more control with the service brakes than you would with an engine brake.

One question I do have for Roshea is exactly how does using the jakes cause excessive tire wear? If it's not causing the tires to skid, I don't see how it could cause more wear.

Again, thanks for all the opinions. Learning something everyday here!

dodgeram440rt · Jan 16, 2010

To the mod who moved this thread:

If this is the appropriate area for this thread, then so be it. I'm a new driver with a question for the experienced guys so that is why I posted where I did. The issue I have here is loosing my thread. This is the second time a thread I posted got moved to a different area with no notice or indication to where my thread went. I had to hunt and search thru the sections to find my thread. On other forums I'm a member of, when a post gets moved, there is a notice and a link to the new location. Perhaps this might be useful in the future.

FWIW, I still feel the correct area for posting this was in the newbie questions where I first posted it. This wasn't about the technical functions about the operation of an engine brake. I was simply asking a question about if it's right to use an engine brake when downshifting and the opinions of the best times to use them.

Thanks.

black_dog106 · Jan 17, 2010

dodgeram440rt said: ↑

I'm afraid I've started a war between the old hands here. I really appreciate all the responses and the opinions. Everyone has their own methods of driving and to say one is better than the other would be wrong. Obviously both methods work for their respective drivers.

I do have to say that all of the training and schooling I have been thru up to this point say that you should NOT use the engine brake in any kind of slick conditions. I don't know, that just seems like common sense to me. While I have not driven a big truck in the snow (yet), I have lived in snowy climates all my life so I know about winter driving. In this particular case, I have to agree with Roshea, that the braking power of 18 wheels would be far better than that of only 4. You have way more control with the service brakes than you would with an engine brake.

One question I do have for Roshea is exactly how does using the jakes cause excessive tire wear? If it's not causing the tires to skid, I don't see how it could cause more wear.

Again, thanks for all the opinions. Learning something everyday here!
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pm sent.........

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