Engine brake

A Jake will slow only the tractor down with nothing slowing the trailer down. Same thing as if you had no trailer brakes and pressed on the service brake. On slick roads this will make the trailer try to swing out (jacknife).

I fail to see how using a Jake with a Johnny bar will cause a jacknife.

 

I have watched a truck going down hill on snowy interstate to build up speed for the next hill then start up the hill, loose traction, spinout and the trailer jackknifed to the right and put him in the ditch. The momentum of the trailer caused this jackknife. Location east bound on Elk Mtn, Wyo.

 

Off topic- if it is slippery out is it ok to lock the axles while moving? I assumed this should only be done at low speeds, or no speed

On topic- I didn't know that about keeping the brakes dry. Generally running hills you're on and off the brakes usually. Thanks for a new piece of info.

 

NO!

Jake will slow down only the tractor wheels. Wheels need traction to slow down the vehicle. That is a very important distinction.

With all the braking force on the center drive wheels (with the jake) you are likely to loose tractive stability with those drive wheels and initiate the jackknife.

As the drive wheels loose stability and slide, hitting the spike will transfer weight to the drive wheels from the trailer and produce a braking force to the tractor that will have a tendency to straighten out the assembly. The down side is of course, the lack of tractive force that caused the tractor to slide in the first place is also likely to cause the trailer wheels to lock up and slide also. Thus it is perhaps more likely to make the jackknife worse rather then less when trying to straighten with the spike.

When driving on slick surfaces it is always better to apply outside forces (braking, steering, and acceleration) as smoothly and evenly as possible. The brake peddle is best at evenly distributing those forces. Relying on one set of wheels to brake more then the others is a mistake in every sense.

 

I would lock my power divider on snow covered roads but keep speed at 50 max usually slower. I didn't lock the power divider on wet pavement. I have been forced to chain in calif to go over Donner and get over to find the roads were wet but no snow or ice. Stupid caltrans

 

Here's the deal. Applying brakes,jakes or retarders will cause loss of traction at some point. Just like driving to fast for the conditions. So if you apply a slight amount of throttle while braking it keeps your tires from lossing traction because you are rolling them instead of trying to completely stop them. This also stretches the truck. There by decreasing the chance of a jack knife. So Lucy was sort of getting it but just the wrong application. Its just Physics. Now some of you drivers may think I'm talking out my tailpipe but I do have 40 yrs behind the wheel and it wasn't Interstate trucking. I would be glad to answer any refutes. Good day

 

For those of you who worry about jackknifing remember at the first sign of that push your clutch in or shift to neutral.

 

Why? Please explain more

 

So all the wheels may move freely and naturally regain traction. Coasting is the next best thing, but pushing the clutch in completely frees the drive wheels from engine forces. Even with the engine brake off, there is a small amount of engine braking going on when you are off the throttle.

 

Oh boy. This thread is going off the rails quick. It's no wonder new guys have such a hard time learning practical skills while training under "mentors". So many tips that go completely contradictory to other tips. And some border on malpractice.

Good luck driver sorting through all this information. But like I said, experience is the only way you'll figure it out.

The abundance of truck crashes that seem to accompany every winter weather event is beginning to make sense.