Non Moving bolted 5th wheel?

Simple physics. In a hard braking situation, weight transfers forward. So what happens when the trailer brakes pull down on the nose of the trailer, increasing the weight on the drives? The steer axle gets even lighter. Granted, you also have the tractor weight transferring forward onto the steers as the drive brakes pull the front end of the truck down, but if conditions are slick it just seems like it could make a bad situation go sideways in a hurry.

In a car, 70% of your braking is done on that front axle because of the weight transfer. I've not seen any numbers like that to say what percentage of the braking each contributes on a 5 axle T/T, but I'd imagine it works much the same way. With the new braking standards, I've heard the difference between drum vs disc brakes on the trailer are negligible, while you see more gains (shorter stopping distances) using disc brakes (or larger drum brakes) on the drives and steer axle. I realize that in years past, tractors didn't even HAVE brakes on the steer axle, and those that did often had a limiting valve to reduce the functionality of those brakes while bobtailing or in slick conditions. I can sort of understand the whole bobtailing thing, because if you don't have any weight to transfer up onto the steers you increase the likelihood of locking them up...however, WITHOUT brakes on the steer, it'll take forever and a day to get stopped as braking transfers weight off the only axles that have brakes.

In any case, though, having the trailer's weight transfer lightening the steer axle when you need to get stopped (and possibly steer around whatever is causing you to brake hard) just doesn't seem like it would be even the least bit beneficial. It may not be that big of a deal...but i'd rather not be the one testing that hypothesis.

 

I didn't even think of that. Good point.

 

I would have to see a picture. What a previous poster said you may have a 14,000lb front axle.
That what it looks like with that weight ticket. Did you look at the door sticker?

 

For theatrical effect I'll roar BS and slam a fist on the counter. Your steers do not lighten *&^% under hard braking with that weight transferring forward.

Now Im pretty sure you have a kernal of truth somewhere in that one sentance statement that will bite me and cause me grovel while prostrate for your forgivness. But until then Im pretty strong in feeling that steers do not get lighter under braking. Everything goes forward eight wise;.

 

Generally speaking, yes. Weight transfers forward under braking. However, you have to look at the tractor and trailer separately as well as their overall effect. The trailer transfers weight onto the drives. The drives transfer weight onto the steers. If the trailer lightens the load on the steers the heavier it gets as you load the trailer, it would have the same effect as that weight transfers under hard braking. That leaves the question as to how effectively the tractor can shift weight onto the steers. Given the wheelbase advantage of the trailer over the tractor, I would say the leverage of the trailer brakes pulling down on the nose of the trailer will be capable of transfering more weight onto the drives than what the drives will shift up to the steers...leaving the possibility of potentially lightening the steers as you brake. This is an untested hypothesis, though. The steers might have some weight transferred to them under heavy braking...but if the weight transferred to the drives from the trailer counteracts the weight transfer to the steers from the drives, your braking won't be as effective because your steers aren't getting the weight added that they need to get you slowed down in a hurry.