Friday, August 23, 2013

Excellent MUST READ - article on Cargo Trailer Axle Rebuild, after only 800 miles

This article is from Rob @

Rob also has a photobucket account with lots of trailer pictures,

also you can see a complete trailer rob has rebuilt Click Here  

Please go to his site for additional articles, since it is so great I have decided to reprint it here because it is really a must read for anyone who tows a cargo trailer with leaf springs, so 90% of the crowd.

The trailer has around 800 miles on it. 
So, 800 miles, and the trailer is only 2 years old...
should be ready to hit the road, right?
Maybe, but follow along with the pictures of the rebuild, and you may decide otherwise...


First, these trailers are designed to carry a fair amount of weight, inexpensively, for reasonably short distances. To accomplish this goal, the trailers are made pretty lightweight with a minimum of materials to keep them affordable. Carrying a decent amount of weight, but forgoing comfort, allows the use of short leaf springs.

Short leaf springs will carry a lot of weight. Long leaf springs will carry less weight, and cost more, but are MUCH more comfortable. For those who don't have trailer towing experience, short springs equal a very bouncy stiff ride, while long springs equal a very soft smooth ride. No big deal if you just tow your trailer a few miles a couple times a year, but pulling a trailer that bounces means you'll feel a tug in your tow vehicle at each bump in the road...not a pleasant way to travel several thousand miles!
To be fair, it should be understood that the closer you get to the trailer's maximum designed weight capacity, that is, loaded down, the ride will improve somewhat.  When 2000-2500 pounds (close to what a 2990# capacity trailer can safely carry) are placed in the trailer, the springs will flex and the ride will be decent. Pull the trailer empty, or with just a portion of the maximum allowed weight, and the springs will act more like a solid suspension (without springs) because there isn't enough weight to make the springs flex.
Consider that leaf springs flex, or flatten out as weight is applied. In order to flex easily, the surfaces of each leaf should be clean and smooth. Trouble is, the thin coating of paint that is applied to the springs when new seems to last for only a year or so before it rubs off and rust starts to form. Once the leaf spring surfaces are rusty, the leaves can no longer slide easily against each other. This causes the ride to be even stiffer, and the trailer to bounce even more. Add to this the trailer tires that are inflated to the recommended 50 PSI to carry the fully loaded trailer, and the stiff spring's lack of action is amplified further.
My friends trailer rode very poorly. It bounced, tugged, and had a bad vibration caused by the wheel/tire combinations not being balanced.
In renovating/preparing the trailer for long distance towing, I had 4 main goals;
#1, Balance the wheels.
#2, Replace the wheel bearings and races
#3, Rehab the rusted leaf springs and spring hanger system
#4, Reduce the weight rating of the leaf springs from 3500 pounds, to 2500 pounds
   Let me start by explaining why I want to reduce the carrying capacity.
My friend bought the trailer for a specific purpose, and thus will haul a set amount of weight. Since we know the combined weight of his motorcycle and the items he'll be transporting, and the empty weight of the trailer, we can easily calculate how much capacity the springs will need to bear. 
Since the total combined weights don't come near the designed weight capacity, reducing the spring capacity will allow the trailer to be nearer its optimum weight for comfortable towing.
His motorcycle weighs 450#, and he'll be hauling 300# to 400# of additional cargo. So, 850 pounds total. Now we must add the weight of the trailer itself, which is 850#. That makes a total of  1700 pounds.
The reduced capacity of the springs now totals 2500#, leaving 800# of payload capacity available.
The spring capacity is reduced by removing the lower (shortest) leaf.
I determined, by contacting the manufacturer, that our 4 leaf springs are rated at 1750# per side. Both sides combined equal 3500 pounds. The axle is also rated at 3500#.
Their three leaf springs (the same 4 leaf spring with one leaf removed) is rated at 1250# per side Both sides combined equal 2500#
Of course I've saved the extra leaves, and will attach them to the interior wall of the trailer so if we ever find we need more capacity, or sell the trailer, they can be reinstalled.
Next is item #1; the wheels.
Being an inexpensive trailer they saved a little money by simply mounting the tires on the rims and bolting them on, its just a trailer, right? Why bother balancing the wheels...
I had my son (who has the latest wheel balancing and diagnostic equipment available to him) checked road force, and balance on all three wheels (it has a spare). All three were very far out of balance, 4-8 ounces out of balance!. No wonder there was a vibration from the wheels!
Now item #2; Replace wheel bearings and races.
With only 800 miles on the trailer, you might wonder; why not just regrease them and hit the road?
Well, the first cause for concern was that the rubber grease cap plug on one side was missing.

The trailer had been sitting for two years. How long it had been missing the plug was unknown, but the rust from the hub nut that had discolored the visible grease was enough reason to suspect it had been off for a while.
The second concern was that the rear grease seal on the other side had been leaking.
Further investigation showed that the area of the spindle that the rubber seal rides against was rusted, and rough. It had simply worn itself down.
I used emery cloth to smooth and polish that portion of the spindle.
Since replacement kits containing bearings, races, and seal only cost about $15.00 per side, it made no sense to waste time cleaning and regreasing possibly damaged bearings.

I removed the old races (the part with a machined surface that the bearings ride against) and sandblasted and painted the hubs. Then I used hot soapy water to clean the inside of the hub to be sure no traces of the abrasive remained. 
Then I installed the new races.

Next, I greased all the new bearings, and installed the large, or rear bearings, then installed the new grease seal.
This axle is drilled and tapped with a grease fitting, to allow fresh grease to be pumped to the rear bearing.
Once the grease seal is installed, the rear bearing cannot be accessed without destroying the grease seal…
Before installing the hub, and front bearing, I used my grease gun to pump fresh grease through the spindle so any old grease that remained would not mix with the new grease.
Here is a picture of the back side of the hub. The gold colored ring is the new grease seal.
And here is the hub, installed on the spindle with the new grease cap. Once I add a little grease via the fitting visible in the center of the cap, I’ll install the rubber plug.
And last, item #3; Rehab the rusted leaf springs and spring hanger system
So the springs are a little what, you might say? Most springs are.
Springs are exposed to the elements for sure, they are soaked from every mud puddle and rainstorm you drive through, they collect salt and ice melting chemicals in the winter, they just get a lot of abuse!
Springs that get rusty simply cannot work as designed, that is, they loose the ability to slide against each other as the leaves flex.
Less flex equals a rougher ride. Why should you be concerned with how the trailer rides, after all, no people are in the trailer while its being towed, right?
While no people are in the trailer to be bounced around, your cargo is...and the trailer is connected to your tow vehicle, which will have every bump and bounce transmitted to it through the tow ball connection. As I pointed out earlier, if the trailer is only used for short infrequent trips around town, it won't matter so much, but if you tow the trailer many miles a year, and prefer a smooth comfortable ride, it matters!
Here is a look at one of the spring sets.
And here is the same set after sandblasting the outside.
While it sure looks better, cleaning the outside doesn’t do anything for the ride, here is the set after taking it apart, showing why they need to be cleaned.

Before we get back to cleaning and painting, I’d like to point out another easy upgrade that can be done while the springs are apart; Springs are square cut on the ends. Over time, a spring set that rubs back and forth against the adjacent spring can wear a groove, or recess. Once this happens, the spring can bind, which won’t allow it to flex.
This problem, or possibility can be removed simply by grinding a bevel on the ends of the leaves that make contact with other leaves.
Now that the bevels have been ground, I can paint the spring leaves.
I applied three coats.
Here, I’ve applied a generous coating of high quality grease. The gray powder sprinkled into the grease is graphite. Graphite is a good lubricant, and along with the grease will allow the spring leaves to slide against each other with ease. The grease will also help to keep moisture out.

Here is the completed set, minus the 4th leaf that we won’t be using.

The spring sets are now ready to be reinstalled on the axle.
The last upgrade I’m going to make is with the shackles and shackle bolts. These are the parts that hold the springs/axle to the trailer frame.
The picture below shows the old shackle bolt (silver) and the old bushing (yellow).
The old bushings are made of Nylon. They work okay for allowing the bolt to move in the spring eye as the springs flex, but don’t last very long. When they wear out, the bolt stars to wear, and also grinds away at the metal of the spring eye and spring hangers (the metal brackets that are welded to the trailer frame).
The black bolt, along with the bronze bushing is the upgrade. The bolt is called a “wet bolt” because it is drilled and tapped, like the spindle, to allow grease to be pumped through the fitting in the end of the bolt, to an opening in the center of the bolt. When the bushing is installed, grease will be pumped between the bolt and the bushing, providing constant lubrication.
This is what the old bolts and one of the shackles looked like after only 800 miles…no lubrication…
Here is the bronze bushing partly inserted into the spring eye.
And here is the wet bolt going through the bushing.
The wet bolts came in a kit with new heavy duty shackles.
As you can see in the last picture, there is 1 wet bolt that holds the shackles to the trailer frame, but there isn’t any reason to pump grease into it, as there is no bushing. It is supposed to be this way… I decided to put the old nylon bushings to good use. I cut them to length so they would fit between the spring hangers welded to the trailer frame, and inserted them over the wet bolt. Now the grease can be pumped into the nylon bushing, and squeeze out where the bolt rides against the hanger, offering lubrication.
Here are a couple pictures of the axle being bolted back on.
When the work was finished, the trailer was tested at 75+mph both loaded and empty.The trailer rides very well!
Everything is well lubricated, lights all work, coupler and safety chains are in good order, and the tie downs and accessories are installed inside.
Now it is ready to hit the road!
Here are a couple of parting shots; the accessories installed, and the bike loaded up!
I spent in the neighborhood of 16 hours labor and $120 for parts rehabbing the hubs, springs, and wheels. Well worth the effort and expense considering my friend will be pulling the trailer more than thirty three hundred miles round trip each year.
It goes against the grain to have to spend good money to "fix" something that is new, but...
As with most consumer products, there is a demand for "inexpensive".
We all appreciate a low purchase price, but we must not overlook what upgrades the manufacturers omit in order to meet our desire...
My friend bought this trailer for a very good price. So even after all the upgrades, he still has less invested in it than the average NEW cargo trailer sells for, and it is much better than a brand new model that still needs upgrading. If you're considering buying a new trailer, you might want to think about spending a few extra dollars up front for the upgrades as it is less expensive than rehabbing the trailer down the road, and FAR better than having to call a tow truck...
If you have an old trailer, it isn't that difficult to make it ride "better" than new!

AGAIN - This article is from Rob @

Please go to his site for additional articles, since it is so great I have decided to reprint it here because it is really a must read for anyone who tows a cargo trailer with leaf springs, so 90% of the crowd.


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