Replacing an Axle - leading arm to trailing arm

[Roy in TO]

Background

We bought our 1972 boler American knowing it needed a lot of work to restore it. Our trailer tracked fine during the initial 10 hour drive to its new home even though we thought it sat a little low. We had a big trip planned two months down the road and had a lot of work to do. We did what we could, when we could, where we could. New tires were installed while at Bolerama 2006 and they scrubbed the wheel wells on the way home. Link to tire change post.

With less than 10 days to go before our big trip, we knew we had to do something before we left. We got a local welding shop to cut off the old axle, – weld 2x2” square tubing to the underside of the frame and weld the axle back on. It was a cheap quick fix that worked not only for the trip, but also for the next year or so while I researched axles here and elsewhere on the web. There was a lot to learn about axles and a lot of varying opinions to filter through.

On the way home from our 1st big trip we came within inches of T boning a police cruiser as it came flying through an intersection against the lights. I distinctly remember the wide open eyes of the officer in the passenger side of the cruiser as he watched the front of my truck bearing down on him. The sound of squealing tires competing with the siren. Carol Ann remembers the faint single thank you wave as I finally stopped as the officer’s window passed her side of the truck. Once the adrenaline rush was over and the heart rate came down to normal my mind switched from uttering a flow of expletives to proclaiming the trailer was getting electric brakes if at all possible.

Once home we started to learn more about torsion axles. We compared our trailer to lots of pictures on the web, then read many posts on what others have done. Our 34 year old trailer showed all of the following:

1. Low riding appearance

2. Less than 3” clearance from top of tire to wheel well

3. Tire marks on wheel well

4. Minimal torsion movement in axle with “bumper bounce test”

5. Things bouncing around in the trailer, jumping out of cupboards etc.

6. Uneven tire wear

All this led us to believe we still had the original axle that needed replacing.

Comparing the specs for both Dexter and Flexride (2200 Lb axles) at the recommended down angles (10 and 24 degrees respectively) both provide for about 3.25” (+/- 0.1”) of movement of the spindle between no load and shock load. Dexter has a little more movement between no load and loaded, that is trailer off the ground and trailer setting on the ground. Dexter is at 2.34” and Flexride at 1.69”.

The spindle should drop about 2” when you jack up the trailer. When setting down on the wheels the trailer should have about 1.25” of movement between the body of the trailer and the top of the rim if somebody is jumping up and down on the bumper. If these numbers are out of whack, chances are your axle needs replacing.

Another way to check to see if your trailer is riding low is to level the trailer on level ground using the tongue crank and no jacks. Then measure the height from the ground to the floor at the door and compare that to the specs for your trailer. For the boler American, total height is specified at 6’ 11”, inside height 6’ 1” giving a difference of 10”. That should equal the height of the floor at the door.

There are a great number of discussions on leading arm vs. trailing arm configurations for these trailers. Many of our trailers came with the leading arms which have worked well over the years. Today the axle manufacturers recommend the trailing arm configuration. There are some reports of manufacturers saying that a leading arm is still OK. Consensus for leading arms seems to indicate that a low down start angle to up angle is what is recommended and that a high down angle be avoided.

Some have reported using brakes on a leading arm arrangement. This usually requires switching the brakes to the opposite side since brakes are left and right handed and all axles are currently manufactured on assembly lines to be trailing arms. For our trailer I chose to install a new trailing arm axle with electric brakes. I felt this would be the safest and that it could be done without major modifications to the frame.

Changing to a trailing arm, requires raising the trailer about 3.5” to allow the main bar of the axle to be located under the dropped kitchen floor rather than behind it. Raising the trailer can alter the center of gravity of the trailer making it more unstable side to side. I tried to keep the amount of rise to a minimum for stability, appearance, function and towing considerations. By using the smaller diameter tire and zero degree angle the net change was more in the line of 2.5” higher than stock. Considering the trailer had probably settled 2.5” over the last 36 years, the net change was approximately 5”. Raising the trailer also reduced the air dam effect experienced in towing with my 4x4 Ranger.

In all honesty, it was a complex decision to make. I had to put all the specs for the various axle manufacturers into a spread sheet to compare the final ride heights and space under the wheel wells to accommodate the movement of the tire and axle. I then added various tire and rim dimensions into the spreadsheet to find the best match for my wants and needs. Keep in mind the original 6.00 – 13” tires are no longer available.

Many of the Bolers and its descendants have the body offset from the center of the frame by an inch towards the street. Some have stated that this is to balance the weight from side to side. I do not think that is the case because the side with the greatest weight is furthest from the frame. I feel this was done to maximize floor space by keeping the frame as close to the curbside closet as possible. The wider kitchen counter allows for the frame to be set further in without affecting floor space.

This in turn keeps the curbside of the trailer more in line with the passenger side of the tow vehicle, while the streetside extends further out from the TV. The end result is the wheel and tire end up closer to the outer body on the curbside than on street side.

How I did this will follow in the next few posts.

[Roy in TO]

This is what our trailer looked like when we picked it up.




It sits quite a bit lower than the one shown in this 1976 brochure. Note the position of the tire and rims to the body.




The original axle has the following information plate welded to it:




Which reads:
INGERSOLL RUB-R-RIDE
MFG. UNDER NEIDHART PAT.
CAPACITY 1200 LBS.

The tag on the trailer lists the weight at 850 Lbs. with a maximum gross weight of 1250 Lbs. Note the trailer is rated higher than the axle. It is known that the early trailers were understated for weights with actual weights coming in at 1000 Lbs or more empty. It is not too hard to put in over 200 Lbs in gear. These axles probably spent their entire life at or over their rated capacity. Below on the left is a picture of the axle from another boler American, on the right mine.




Both axles are positioned higher than what I believe was initially a zero degree start angle. That is the arm should be parallel with the frame under load. Mine on the right was quite a bit higher.

Continued …

[Roy in TO]

The quick fix.

The tire on the left was the original 6.00-13, the middle the P165/70R13 car tire that was on the trailer when we got it and the tire on the right a ST 175/80R13, the recommended replacement ST trailer tire.




In hindsight it is quite easy to understand why the trailer tires scrubbed when I installed them. My torsion arms of the old axle had the spindles located about 2” higher to the wheel well, and the larger tire added another inch. There goes my recommended 3” clearance and the tires would scrub over bumps in the road.

The quick fix was to weld a 2x2” square tube between the frame and the axle.





I didn’t notice this until composing this post, but the picture on the right shows the bent torsion arm and spindle. Note how the top of the tire is canted inwards where is should be canted out. No wonder I got such excessive tire wear on the curbside tire.

The temporary quick fix raised the trailer making it look a little more like it should and stopped the new tires from scrubbing.




Though it still does not look like the trailer is sitting high enough, it did get us through a 3 week trip to the East Coast and the better part of 2 ½ years till we could get the new axle installed.

Continued …

[Roy in TO]

The final modification …
· changed the axle from a leading arm, to a trailing arm configuration

· centered the axle under the body instead of the frame.

· Raised the body a little more and

· added electric brakes.

The challenge was getting everything to fit just right.

After a lot of research, measuring and calculating I came up with this diagram of a cross section of the trailer through the wheel wells.




The diagram below from Red Neck Trailer provides some clues as to the clearance required for the electric brake drums.




The original hub face to hub face was 64”, allowing a minimum of 6” for each drum leaves 52” between the drums and less than an inch clearance on the curbside if I was to center the axle under the body. So I chose to go for a 64.5” hub face to give that extra room. The key to shifting the axle was to move the mounting brackets ½” curbside from center. Dexter Engineers said it could be done but the assembly line said they couldn’t.

The decision was made to space the mounting brackets 1” more and change the streetside rectangular steel to 3” wide and this would shift the axle over the ½” required centering it under the body. I then used a spreadsheet to compare various axle angles in combination with various tire/rim combinations to get a final hitch height between 17” and 18”. The best combination came from using a Carlisle premounted ST145/R12 and a Dexter Torflex axle with the following specifications:

Dexter # 9 Torflex rated at 2200 Lbs.

7” Electric brakes 5 on 4.5” hub with EZ lube

Standard inboard mount with hanger kit

0 degree

50” to Outside of Brackets

64.5” Hub Face

This is what the frame looks like once the axle has been removed.




Streetside




Curbside

When it came time to weld, the welder did not have any 3x4” rectangular tubing for the streetside, so we used a 2” wide and left the streetside bracket overhanging by ½” from the frame extension. The metal was cut a little longer than the length of the axle mounting brackets, flaring out 45 degrees to the frame on either side. The wheels were put onto the axle and the lifts clamped onto the mounting brackets. The entire assembly was lifted into place. A notch was cut into the center U Channel under the floor to allow for the axles camber and everything was checked for the correct positioning and alignment before welding into place.




The notch is just above the welders head shown above.

And a close up below.




Continued …

[Roy in TO]

Streetside view




And Curbside view:




The angle on the curbside closest to the door had to be notched for the frame support.
This is best seen looking from inside the frame as shown below:




A little closer view




And as viewed from the outside




Continued …

[Roy in TO]

The size difference between tires is shown below. The final ST 145/R12 is on the left, the original 6.00-13 in the middle and its recommended replacement the ST175/80R13 is on the right.




Once everything was installed this is how the trailer looks.





The trailer feels and sounds like it has less resistance towing now that it is a little higher. Things no longer fly around on the inside while towing. I can definitely feel a big difference in stopping with the electric brakes. I am not as scared about having to stop fast while driving. It is a major reduction in stress.

The axle with brakes cost a little over $400 CDN including taxes. Installation $300 CDN, 3 new tires and rims about $300 more. Total cost was just over $1000 CDN plus a few hundred hours of researching, measuring and planning.

You can read about the entire chronological restoration of our trailer here.

[Raya]

Roy,

This is great information - thank you for taking the time to post it so well

(Quick note about the 1250# gross weight vs. the 1200# axle capacity: I bet they were subtracting the 50# difference for the "unsprung" weight of the axle itself. Of course that's still under-rated for how most people load their trailers; I'm just noting where the "missing" 50# might have come in.)

Looking forward to the rest...

Raya

Edited to add that that the axle, rims, and tires would probably be more than 50# in actuality - probably closer to 200#? So that "gives" a bit more favor to the lower axle rating as compared to the actual trailer weight. (Sheesh, it's hard to explain what I mean!)

[Pete Dumbleton]

I agree with Raya about the 'missing' 50 lbs. Nice job of replacement and documentation!

[Roy in TO]

I thank both of you.

[Raya]

Your Boler sure looks perky with the new axle!

[Alf S.]

Hi: Roy in TO... Looks like the new axle has given you quite a "lift". Do you need a step stool to get in now???
Alf S. North shore of Lake Erie

[Andrew Gibbens]

I bet they were subtracting the 50# difference for the "unsprung" weight of the axle itself.

More likely it was the tongue weight that made the difference - 1250lb gross trailer weight less, say, 150lb tongue weight is 1100lb, so well within the 1200lb axle rating.

Andrew

[Carol Ann in TO]

Hi: Roy in TO... Looks like the new axle has given you quite a "lift". Do you need a step stool to get in now???
Alf S. North shore of Lake Erie

Alf: now that you mention it, I remember "tripping" into the trailer on the first trip away with the new axle.

Carol Ann

[Bill D]

With all the time cutting, welding and measuring, is there any reason one couldn't fab some kind of spring hangers and install a regular axle with leaf springs? (just thinking out loud) Bill

[Roy in TO]

is there any reason one couldn't fab some kind of spring hangers and install a regular axle with leaf springs?

3 thoughts come to mind.
Since the kitchen floor is 3" lower than the bottom of the frame you would have to raise the trailer a little too high to get everything to work under the trailer with a straight axle.
If you used a "drop" axle (the spindles are higher than the axle), ground clearance would be in the 4-6" range.
3rd reason is that the frame ends at the door. One may not have enough room for shackles unless you are using really short springs.

[Raya]

Andrew,

Oh, interesting - I hadn't thought about counting tongue weight as "unsprung" weight along with the running gear itself (axle, rims, tires, brakes).

Now I see even more how the earlier trailers could use a 1200# axle (although it may have been a bit light - and they did switch to 1600# - now it's not as crazy as it first sounded). Thinking out loud:

If the rig weighs 1600# loaded, you could now subtract
Tongue weight of 200# (12.5%)
Running gear weight of 200#
So your "sprung" axle weight is ...1200# exactly.

Still a bit close, and certainly not what I would purchase now, but not as crazily low as I had been thinking. Subtracting the tongue weight makes a big difference.

But... are we sure that's correct? What if one is going up a hill and/or over bumps? Do you still "get" to subtract the tongue weight?

Raya

[james kent]

Raya
That's like asking, "How much does a pound of cement weigh if your flying at a thousand feet?"

So the answer is ....YUP.

[Alf S.]

Hi: All... Trailer weights are subjective... Like the age old question "Whats a Greecian urn"??? I always look for the Gross Weight rating for the axle and work backwards from there!!! I seem to do best working BACKWARDS!!!
Alf S. North shore of Lake Erie

[Raya]

James,

I just wasn't sure if, say, you were driving up a steep, bumpy hill, that some of the tongue weight would not be shifted to the trailer axle. It still seems to me like it would, but I'll accept that it must be one of those things that seems to be true but isn't.

So that does take that 10% - 15% off the weight that must be applied to the axle's rating then (along with the unsprung weight of the running gear itself).

Good to know.

Raya

[Pete Dumbleton]

I would expect the axle's rating to include the normal use of up/down hills and in turns where the weight is shifted to one side or the other. They specify a static weight because that's the easiest to measure and is understood by all.