Effects of trailer brakes and sway

[flhtci2006]

Picture this hypothetical situation: Tandem axle trailer, weight distribution/anti sway hitch, tongue weight 12.5% of trailer weight, trailer at or near (not over) max gross weight, trailer to tow vehicle setup correctly (in other words, all setup is proper).

Could misadjusted brakes induce sway? Could dragging or locked up brakes initiate sway? Since it's a tandem (dual) axle, is there a brake situation that could better induce sway, such as just one brake, 2 brakes in line, 2 brakes cross corner, etc? So, we're looking at the effects the brakes have on stability/sway. Any mechanical engineers out there with time and a sharp pencil?

[JBarca]

Turtle n Peeps wrote:
I think Mikes point is there is no (built in) toe in a trailer axel. I agree with him.

Is there a spec? Sure! There is spec's for everything. Otherwise people like me would put a set of gauges on a brand new axel and reject it because it has .07 degrees of toe in it. This way the manufactures can say, "that's within our spec's so it's fine."

Hi Turtle n Peeps,

I am "thinking" by your response there is miss-understanding on the word "built in". I can tell you agree as I do, that toe on a trailer axle since it does not steer is in the 0 degree range. And yes there is a specification for toe of the axle which comes in the form of a tolerance based around the 0 target. I think we agree on this? Yes/no? Think about this process I'm describing below.

Now to how do they "build" an axle. The axle spindle shafts or stub ends, (the machined ends where the wheel bearings are with the brake drum or hub) are machined at a separate operation from the main axle tube. The axle tube is made from a certain grade of steel, size and wall thickness pending the load rating of the axle. There is a welding process that joins the axle spindles to the end of the axle tube. This is a critical controlled process so the heat shrinking of the weld does not distort the position of the axle spindle ends. If the welding warps the spindle joint wrong, the toe settings can be very far off of where they are supposed to be.

Trailer axles also have camber built into them. Pending the load rating they bend the axle in the center up in relation to the top of the axle to a specification with a tolerance to create a positive camber setting at the wheel location for the load rating of the axle.

There is also the axle seat installation as well as well as a brake plate mounting ring if it they are making a brake axle. They install (fabricate, build etc.) the axle seat from a formed sub-assembly and pending the weight rating, they may add reinforcement plates on the ends of the axle seat in that sub-assembly. These axle seats are then welded onto the axle tube in relation to the center of the axle left to right, and for "radial" positioning. The brake mounting plate ring also follows this radial positioning. They find the "top" of the axle tube which we will call 0 for this discussion. The bent camber setting is up and on top at this 0 mark. They clock or rotate the spring attaching side of the axle seat so the camber and toe setting built into the axle are within an acceptable tolerance when the axle seat side is mounted to the leaf spring which is at this 0 or 12:00 position. The axle seat spring mounting face is true horizontal when at the 0 position as viewed from the spindle end. If they welded the axle seat many degrees off radial position, say 5 or 10 degrees out of location of the zero mark, then the axle toe setting can be affected at the wheel as the camber bend in the axle tube would rotate the axle spindle end to no longer be in the correct plane. If the axle was true straight with no positive camber, then it would not matter, but we have positive camber and need to deal with it.

After all this welding and bending is done they have a QC check to insure the axle assembly is built within their specifications for all the important dimensions. Toe and camber are created at the wheel by being built into the axle assembly. Toe and camber are considered non adjustable short of some repair shops bending the axle tubes trying to get them back into specification.

There are other steps in the making axle assemblies I'm sure I did not list, but what I did list are some of the larger points I was trying to make. My point was they are "building" the axle with a toe setting "built into" the assembly on purpose. In this case the setting is 0 degrees with a tolerance range at the wheel.

I'm assuming you may agree with the process I described above in general terms as I can tell by your responses you agree we have a 0 degree target. If they did not build in a 0 setting for toe then the toe at the wheel could end up being excessively in the wrong place and never work correctly.

That is the context of the wording "built in" I was using. What were you referring to when toe is "not built in"?

Hope this helps explain this better.

John

[BenK]

Back to the OP's question..."Effects of trailer brakes and sway"...

No, uneven braking and/or dragging trailer brakes of one side does NOT cause sway

First, understand what trailer sway is...here are some links and youtube videos that might help understand what it is...


Trailer Sway Hensley Mfg., Inc. 1-800-410-6580
Hensley....good explaination of what sway is



ProRideHitch Towing Definitions
ProRide...good explaination of what sway is



Trailer Sway 101 (As seen on RVTV)
A good white paper on sway



HowStuffWorks How Tongue Weight Works
A good series talking about the components that cause and solve sway



YouTube Caravan Sway Crash
A good video showing sway using models on a tread mill


YouTube Trailer Sway Control Demonstration
A good video showing them driving a small trailer that is swaying


So...if trailer brakes do not brake evenly, or only one pulls...it will pull the trailer to one side. Sway is 'yaw' where the trailer will swing from one side to the other side....that oscillates back and forth from one side to the other side with ever increasing amounts of yaw...that if not controlled/snubbed/etc...it WILL potentially cause the whole setup to lose control & possibly flip...

Most discussions end up on singular or only one of the components of the whole system that sway control is all about. It is a SYSTEM made up of many sub systems and components...that all add up to the sway control system... Warn to take a step back to see the big picture...AKA 60,000 foot view of the whole. Then drive down each rat hole to see if that one rat hole fixes or makes it worse, etc...

[Turtle_n_Peeps]

I think Mikes point is there is no (built in) toe in a trailer axel. I agree with him.

Is there a spec? Sure! There is spec's for everything. Otherwise people like me would put a set of gauges on a brand new axel and reject it because it has .07 degrees of toe in it. This way the manufactures can say, "that's within our spec's so it's fine."

[JBarca]

mike-s wrote:

JBarca wrote:
I told you where I received the manufacturing specifications for toe from both Alko and Dexter. They build the axles to meet that spec and their quality control checks for it.

Those weren't toe specs, they were simply acceptable ranges. All of them could be a 0 degree design spec, with a tolerance range. I was just asking for a link - something verbal from a customer service agent really isn't authoritative. I've spent enough time with various phone agents to know they can be inconsistent.

You earlier claimed "trailer axles have a toe setting built in from the factory...the toe adjustment can be out of spec if you install the axle tube backwards."

I wouldn't have called that a "toe setting built in," as 0 degrees is obvious. But you then backed off that claim, saying "Yes the target for toe is 0 degrees."

Stuff gets bent, so they provide an acceptable range should stuff need to get rebent back into alignment. 2 of the 3 ranges were such that turning the axle backwards wouldn't make a difference.

At this point, I cannot help you any more. I gave you what Dexter sent to me in writing as what they called their specification which was a target with a tolerance. I did not back off of anything.

If you want a copy, then call Dexter and request it.

[mike-s]

JBarca wrote:
I told you where I received the manufacturing specifications for toe from both Alko and Dexter. They build the axles to meet that spec and their quality control checks for it.

Those weren't toe specs, they were simply acceptable ranges. All of them could be a 0 degree design spec, with a tolerance range. I was just asking for a link - something verbal from a customer service agent really isn't authoritative. I've spent enough time with various phone agents to know they can be inconsistent.

You earlier claimed "trailer axles have a toe setting built in from the factory...the toe adjustment can be out of spec if you install the axle tube backwards."

I wouldn't have called that a "toe setting built in," as 0 degrees is obvious. But you then backed off that claim, saying "Yes the target for toe is 0 degrees."

Stuff gets bent, so they provide an acceptable range should stuff need to get rebent back into alignment. 2 of the 3 ranges were such that turning the axle backwards wouldn't make a difference.

[JBarca]

mike-s wrote:

JBarca wrote:

mike-s wrote:

JBarca wrote:
The reason for this is, trailer axles have a toe setting built in from the factory.

I'd like to see a proper citation to support that claim. Camber is often built in, I've never seen anything saying toe is.

In the link above in my reply you are quoting I typed out the Alko and the Dexter specifications they sent me when I called them.

Got it. You can't point to a reference, just what someone told you. And 2 of the 3 toe specs you gave were simply tolerances for no toe (e.g. Dexter - 0.25 degrees toe out to 0.25 degrees toe in).

Just reading the words on the screen, the context of your note sounds like maybe some disbelief due to a miscommunication of a verbal discussion. I told you where I received the manufacturing specifications for toe from both Alko and Dexter. They build the axles to meet that spec and their quality control checks for it.

Back in 2009 when I needed to change tires on my camper I had noticed a very bad wear pattern on the existing tires. Each tire had a different wear pattern. After seeing this I did not want to install new tires to only get worn in the same manner. I started a somewhat lengthy search for trailer alignment and specifications so I could back into what was wrong. At that time I could not find much of anything in a web search for technical details of what is declared as proper trailer wheel alignment to not cause tire wear. I did find a small amount on semi trailers as they too have tire wear issues when alignment is not correct. Same basic issue as our campers, but the semi trailers are built very different, very heavy duty as the loads are much higher.

I created a technical letter with pictures of my issues and emailed both Dexter and Alko. I called to follow up with both. Alko did not respond as well as Dexter but the Alko service manager told me their axle specs for toe. When calling Dexter, they where more helpful. The service manager told me their axle specs over the phone and emailed me cut sheets of their axle documentation and specifics. The cut sheet called, "Wheel Alignment Check Procedure - Trailers" listed the toe spec I had posted. I looked again this morning in their on line Applications Manual which has been updated since 2009 for this check, however the toe spec is still not listed.

If you want a copy, call this Dexter number http://www.dexteraxle.com/contact-us/contact-form and ask to speak to axle technical service. Sorry I can't link you the cut sheets with the specs but this is how I acquired them.

While you did not ask me, I did ask the Dexter and Alko service manager, what alignment specs do the axles and wheels need to be in to prevent the tire wear I was seeing? They pointed me to their specification and if the axles and wheels are mounted within their specification the tire will wear correctly. I corrected the trailer frame and axle issues to meet all the specs and ever since, my tires are wearing even on all 4 wheels as expected. I had a severe toe out condition creating the heavy wear. The further out of spec, the worse the wear.

[mike-s]

JBarca wrote:

mike-s wrote:

JBarca wrote:
The reason for this is, trailer axles have a toe setting built in from the factory.

I'd like to see a proper citation to support that claim. Camber is often built in, I've never seen anything saying toe is.

In the link above in my reply you are quoting I typed out the Alko and the Dexter specifications they sent me when I called them.

Got it. You can't point to a reference, just what someone told you. And 2 of the 3 toe specs you gave were simply tolerances for no toe (e.g. Dexter - 0.25 degrees toe out to 0.25 degrees toe in).

[JBarca]

Turtle n Peeps wrote:
They have a toe spec, but it's always 0 on every trailer I have measured. Why would it be anything but 0 on a non steer axel?

Yes the target for toe is 0 degrees. But there is a tolerance in parts of a degree. Not whole degrees but 2 decimal places of a degree. Wheel toe often ends up out of tolerance when the axle tubes/spindles are made wrong, bent axle, bent wheel, other failed part or axle tubes mounted or assembled on the trailer wrong.

From my learnings, axle alignment covers: (all with tolerances)

Thrust angle of the front axle to the tow ball/pin
Parallelism of the front axle to the back axle if tandem or triples
Toe at the wheel
Camber of the axle

There is no caster as the wheel does not pivot on a vertical axle spindle during a turn. Well these trailer wheels do flex all kinds of strange directions in a 90 degree turn, but that is not really steering, more of deflecting.

[Turtle_n_Peeps]

They have a toe spec, but it's always 0 on every trailer I have measured. Why would it be anything but 0 on a non steer axel?

[JBarca]

mike-s wrote:

JBarca wrote:
The reason for this is, trailer axles have a toe setting built in from the factory.

I'd like to see a proper citation to support that claim. Camber is often built in, I've never seen anything saying toe is.

In the link above in my reply you are quoting I typed out the Alko and the Dexter specifications they sent me when I called them. Call them and ask for their documentation. Dexter has a very good tech support line.

The axle stubs are installed in the axle tube and or adjusted at the factory so that the toe of the wheel when mounted will be within the spec they declare. This is all in relation to the axle seat they weld on. If you take your trailer to an alignment shop they will measure the toe at the wheel. Pending the shop, some bend the axle tube to put the toe back into the proper range as this is not a user adjustable setting the way most trailer axles are made.

Where you thinking they never had a spec for wheel toe? This is a fairly common trailer alignment spec. I can attest to, if you have an excessive toe out or a toe in condition, the tire will create a scrub angle to the road and wear them at that angle in short order. I had that condition on my camper which brought me to having to research all this and figure out why my tires where being ground up so and correct it.

Hope this helps

John

[mike-s]

JBarca wrote:
The reason for this is, trailer axles have a toe setting built in from the factory.

I'd like to see a proper citation to support that claim. Camber is often built in, I've never seen anything saying toe is.

[JBarca]

flhtci2006 wrote:
So here's the deal: My trailer was loaded to 400 pounds below max weight. Tongue weight percentage was 12.3. I had just gotten the trailer back from a "repair" facility and was getting ready to head to the east coast.

I happened to notice they had installed the axles backwards, rt vs lt, not up vs down. I drove back to the shop to have them reverse the axles (130 miles). They reversed the axles and I headed home. The trailer had minor sway which I thought was canyon winds.

Also, the truck was working harder and gas mileage dropped from 8.9mpg to 5.8mpg. Also, two tires were running 45º hotter than the other two.

Slowed to 35mph in a construction area on a 7º down grade. Upon exiting the construction doing 35, I proceeded to speed up due to the grade.

The trailer then swayed dramatically and caused all 6 hanger brackets to bend, shifting the axles 2 inches to the left.

The road was straight with no bumps. They are saying it's my fault. There are a lot of mistakes they made prior to this (which is why they installed new axles...backwards) that really isn't pertinent.

Hi,

I may be able to add some to the discussion as I can see a several things going on and we do not know what happened exactly when.

First off, yes there is a front and back to the axle tubes. I am talking just about the axle tube at this point. You are correct, the wire hole is supposed to point to the rear of the trailer. The reason for this is, trailer axles have a toe setting built in from the factory. Depending on which axle manufacture makes them, they declare slightly different tolerances. You did not say if you had torsion axles or leaf springs as there are differences in them too. See here, scroll down a little and you can see the tolerancesTT axle alignment & install - Detailed (long lot's of pics)

Bottom line, the toe adjustment can be out of spec if you install the axle tube backwards. Wire hole to the front= backwards. If you manage to install it upside down, bottom on top and top on bottom, not likely but not impossible, the camber will be messed up.

The brakes have a left and right hand also. They do not work well when reversed.

When you took the trailer back, the shop could of goofed up a few things on the axle re-install to even more aggravate axle alignment to be worse. We need to be talking specifics here, the thrust angle on the front axle could be shifted out of spec if the play in the spring seat pin was excessive and fully skewed to the max play. This puts the front axle not square to the center of the trailer. Then the rear axle, assuming this is tandem, could be skewed the other way not making front and rear axle very aggravated in not being parallel. The axle alignment is now out, and if the hangers are welded on the trailer wrong from day 1, trust me it happens, then you can have a very out of aligned trailer grinding up rubber going down the road as the trailer is dog tracking the truck.

BUT... this mega out of aligned trailer will scrub tires badly but you may not get induced sway out of it that you feel "pending" other factors. You did not say what total weight the trailer was or what size truck you have. Do you have antisway control hitch? A heavy suspension truck can help hold this setup more stable then a soft sprung truck with soft tires on it.

Your hangers bent to the tune of the wheels being 2" shifted. This is another issue. We need more info on how your trailer is built. Especially if it is an I beam frame. Pics of the hangers and frame will help greatly. Trailers now a days have many axle hangers issues and are no where considered heavy duty. The side flex of the hanger into an unsupported I beam frame can and will crack the frame web over time. The lower flange of the I beam is so weak it flexes without much side thrust. The hangers if they are the long ones, 3 to 5" long, and have no extra support will bend in turns OR high up and overs on off road travel. The toy hauler guys who go off road often, sometimes reinforce their hangers before they start going in the outback.

Heat in your tires: Between possible axle alignment issues from the shop, bent hangers that then totally messed up the axle alignment, you can easily get heat from tire scrub against the road and it can affect your gas mileage if it is bad enough. You are dragging the trailer down the road rather then rolling it down the road.

Now to the brakes. I just helped my neighbor troubleshoot his brakes. He has a 28 foot, approx 6,500# trailer being towed with a 1 ton SRW Dodge Ram. Only 1 trailer wheel had any kind of braking. The front axle, both sides the wires were broke and on the rear axle, one wheel had a broken magnet coil inside the wheel. He only had 1 brake that had power to the magnet coil and it was very far out of adjustment. That 1 wheel was trying to stop the camper and not doing a very good job of it. There was no sway and the 1 ton truck was doing the braking.

On my camper, 32 foot, just under 10,000# loaded. I installed self adjusting brakes. One brake drum had 0.020" out of round runout to it and that allowed the self adjusting brake to adjust into that out of round and ended up over adjusting it. We are towing to camp and I am in town. I start out from the red light and the truck is up shifting very different. After a short distance of this I pull over and one wheel is smoking hot on the brake. Oh boy.. Let it cool, crawl under and un-adjust it. Here I have been towing out on the highway with a partially locked on brake. And before I could get home, I had to stop a second time and unadjust the brake for the same thing. Point is, I had one wheel almost totally locked on and I'm towing at speed with it. With the mass of the trailer and the size of the 1 ton truck, there was no sway.

To your situation, your rig started swaying on the way back from the shop. First tell us the weight of the camper and the size of the truck. Do you have and anti-sway WD hitch? Think back in your mind, when did the sway start to happen during your trip? Immediately when you left the shop and made it over 45mph or less? Was it after 30 miles of towing above 45mph? or less. There are a lot of factors in what went wrong. This one is not going to be simple to pin point. Once your hangers bent, that is a totally different scenario. The trailer is then severely out of wheel alignment. When was the sway in relation to when the hangers being bent? When did you realize the hangers bent?

Your going to need to find a better shop to do the repair, verify the axle alignment and correct as needed and if your hangers bent, odds are high your frame and hangers are going to need to be addressed so it does not happen again.

Really curious on how this will all play out. We too learn from you on these kinds of situations.

Hope this helps.

John

[RCMAN46]

I believe trailer axles have a little toe in. If the axle is reversed then the axle will have toe out which could possibly aggravate a trailer that is already close to wanting to sway.

My father had a front end shop and he always gave trailer axles a little toe in.

[RinconVTR]

The only way trailer brakes could induce sway is if they pulsed only one side with high power and perfect timing. And that's a big stretch.

More often, applying the trailer brakes will stop sway. That's how the new truck "anti-sway" features operate. They apply the trailer brakes. (In some rare cases, this proves to kill MPG's and create an unpleasant towing experience)


Sounds to me that your dealer messed up installing/reinstalling your axles, they are probably misaligned now, and no way in H E double L is any of that your fault if you never put a wrench on it!