Trailer axle/tire question
- Thread starter zmansmac
- Start date
- Views: 26911
4shorts
Elite Member
Why? I do service and repair work for the Department Of Fisheries here in Newfoundland, Canada and most of there tandem trailers only have brakes on the forward Axel and there all factory trailers that carry very large Boston Whaler boats. Just curious your reason for your statement.
RWolf
Gold Member
- Joined
- Apr 1, 2008
- Messages
- 440
- Location
- Central Texas
- Tractor
- Current, Power King (antique), Soon to have JD 5103
My 2 cents
I would "prefer" to have both axles with brakes. Why? More braking force. I don't know about anybody else but I've experienced brake fade on my trailer and it's not fun. Depending on your controller you can have proportional (pulse), a true proporitional (such as what Ford did) or some other kind of controller. As far as adjusting the controller what I do is (when pulling my horse trailer) I will initially warm the brakes up and after while traveling about 20 - 30 mph use the controller bypass to engage only the trailer brakes. I will set it to stop both the trailer and the vehicle in the quickest time without locking up any trailer brakes. That adjustment will generally provide good stopping force and not rely on the vehicle brakes to much (your mileage my vary ).
I would "prefer" to have both axles with brakes. Why? More braking force. I don't know about anybody else but I've experienced brake fade on my trailer and it's not fun. Depending on your controller you can have proportional (pulse), a true proporitional (such as what Ford did) or some other kind of controller. As far as adjusting the controller what I do is (when pulling my horse trailer) I will initially warm the brakes up and after while traveling about 20 - 30 mph use the controller bypass to engage only the trailer brakes. I will set it to stop both the trailer and the vehicle in the quickest time without locking up any trailer brakes. That adjustment will generally provide good stopping force and not rely on the vehicle brakes to much (your mileage my vary ).
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
I don't think I agree with some of you on the weight transfer on a dual axle trailer. I believe that the front axle will get the most weight in the transfer when braking. I am thinking the back axle will try and rise putting less pressure on the ground. That equalizer thingy is not there to equalize weight transfer, but to equalize the load across a larger area, and stabilize the load in a normal towing situation, and keeping the trailer from bouncing to much.. So if you are giving all the brakes the same current, then the back brakes will grab first because there is less friction, and they will lock up first.. So if you want equal braking on the rear, then you would pass less current to the back brakes. This is only assuming that you are towing the same load all the time, then you can fine tune the controller and using a resistor for the back set of brakes. If you are towing different loads, it will be hard to fine tune and get proper braking action. How many of you have seen flat spots in your tires, most probably the back tires, because they grabbed first. So if you want brakes on one axle, then I suggest the front axle is the one to add brakes to, because it is getting the most weight transfer. I could be wrong, but I don't think so.
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
Ok JJ, did you read my post #29? If you did then why don't you contact the two largest axle/trailer running gear manufacturers in the world, Dexter and Alko, and tell them they are wrong
I'd like to see what they say.
Yes sir. I did read it, but everybody that builds something says that their products are the best and they only used the most correct data in their design, you know that everyone can't be the best. I am just trying to use a little logic here.
Let me ask you a logical question? If you had only so much current to apply to the electric brakes, and the front axle had 1500 lbs on it and the back axle had 1000 lbs on, which axle would stop first. I hope you say the 1000 lb axle. Now if you took some current from the back axle brakes, do you think they might stop at about the same rate with out either set of tires grabbing. I think the front of the trailer tips down in a severe braking situation, and puts less weight on the rear,and more on the front. If you set the tongue weight correctly, about 15%, you already have more weight on the front, so the trailer is out of balance from the git go.
Nope. The weight is roughly equal on both axles regardless of the loading on the trailer. That is why the "equalizer" is there and part of its function. IF there was NO equalizer then YES the load can vary. That is why it is so important to tow a torsion axle trailer level, they don't have equalizers.
Using your logic about the best- find ANY axle manufacturer that recommends other than the back axle in a tandem equalized leaf spring system. I'd love to hear them explain it.
Look at it this way under braking. Trailer is going right to left. When the front axle brakes, which tends to rotate the axle counterclockwise looking at it from the left side of the trailer. What does that do? It lifts the end of the equalizer attached to the rear end of the front spring. And what does that do since the equalizer pivots? It pushes down the rear of the equalizer attached to the front of the rear spring. That in turn increases the load on the rear axle and decreases the load on the front axle. Less load= less braking ability.
Got that? Agree?
Now look at the rear axle, as it brakes it also tends to increase axle rotational force counterclockwise which pushes down the rear of the equalizer, which in turn lifts the front of the equalizer. What does that do? It decreases the downforce of the front tire even more as it is lifting UP on the end of the leaf spring. So now you have even less downforce (weight) on the front tire resulting in even more loss of traction.
It is really all about simple leverage.
Using your logic about the best- find ANY axle manufacturer that recommends other than the back axle in a tandem equalized leaf spring system. I'd love to hear them explain it.
Look at it this way under braking. Trailer is going right to left. When the front axle brakes, which tends to rotate the axle counterclockwise looking at it from the left side of the trailer. What does that do? It lifts the end of the equalizer attached to the rear end of the front spring. And what does that do since the equalizer pivots? It pushes down the rear of the equalizer attached to the front of the rear spring. That in turn increases the load on the rear axle and decreases the load on the front axle. Less load= less braking ability.
Got that? Agree?
Now look at the rear axle, as it brakes it also tends to increase axle rotational force counterclockwise which pushes down the rear of the equalizer, which in turn lifts the front of the equalizer. What does that do? It decreases the downforce of the front tire even more as it is lifting UP on the end of the leaf spring. So now you have even less downforce (weight) on the front tire resulting in even more loss of traction.
It is really all about simple leverage.
4shorts
Elite Member
Nope. The Axels on the goverment trailers are all leaf springs. the torsion system isn't used much around these parts.
Bill_C
Gold Member
I'm mentally going through the free-body diagram of the axles under braking forces, and I see where Dexter and Alko get their answer.
The front axle spring is fixed at the front of the spring. This is the pivot point for the spring; the spring can move up or down as well as laterally at the rear of the spring. When that axle brakes, the friction between the tire and the road exerts a torque on the axle, from both the direct braking torque and the torque that comes from the force of the tire on the road multiplied by the perpendicular distance from that force to the pivot point. Both of these torques make the axle tend to pivot...upwards off the ground.
The reverse is true on the rear axle. The torque acts in the same relative direction as the torque on the front axle, but the spring is fixed on the rear and free to move upwards or down at the forward end of the spring. The axle will be force downward. If the equalizer didn't stop the spring, in fact the axle could even ride under the spring pivot point and flip....
Nevertheless, I will eventually put brakes on both axles of my flatbed trailer.
edit: I see Skyco also explaine dthis at the same time I was typing. Goes to show great minds must think alike
The front axle spring is fixed at the front of the spring. This is the pivot point for the spring; the spring can move up or down as well as laterally at the rear of the spring. When that axle brakes, the friction between the tire and the road exerts a torque on the axle, from both the direct braking torque and the torque that comes from the force of the tire on the road multiplied by the perpendicular distance from that force to the pivot point. Both of these torques make the axle tend to pivot...upwards off the ground.
The reverse is true on the rear axle. The torque acts in the same relative direction as the torque on the front axle, but the spring is fixed on the rear and free to move upwards or down at the forward end of the spring. The axle will be force downward. If the equalizer didn't stop the spring, in fact the axle could even ride under the spring pivot point and flip....
Nevertheless, I will eventually put brakes on both axles of my flatbed trailer.
edit: I see Skyco also explaine dthis at the same time I was typing. Goes to show great minds must think alike
