Replacing leading arm axles

[Andrew Gibbens]

I regret to say I've become an infrequent visitor over here, but I got a query through the teardrops forum that I thought might be useful to repeat here.

A teardrop builder made his trailer frame with a normal Dexter axle mounted backwards - with its arms leading, not trailing like they 'should' be. I suggested he ask Dexter about it, but told him that some fiberglass trailers used to be built this way.

Here is the reply he got from Dexter:

Mounting the Torflex axle with the arm toward the front does not harm the axle. It can have a slight detrimental impact on the ride quality for the trailer. We have had some customers who have ordered their axles with the arm forward because of special clearance problems on their trailer designs. The ride quality decrease is worse with large down start angles and up start angles will not experience much difference in ride quality.

The brakes are left handed and right handed and should remain on the appropriate side of the trailer. Brakes mounted on the wrong side of the trailer will have a slight reduction in performance but a larger reduction in lining wear.

This is quite different from the usual "it can't be done" that some people here have been told when they have sought to replace their leading arm axles. It also repeats the point about ride quality .v. start angle that I suspect was the reason the original axles were mounted this way.

I hope this doesn't just cause confusion where none existed before!

Andrew

[Roy in TO]

It also repeats the point about ride quality .v. start angle that I suspect was the reason the original axles were mounted this way.

Good info Andrew.

FWIW, my research indicates the best "ride" angle for Dexter is 10 degree down, which gives an approximate zero degree under load.

I'll have to check my notes, Flexride specs are different for optimal ride.

Roy

[Benny K]

I may be wrong, but if you reverse the axel it will affect the built in toe in......the axel should have to be designed either for toe in or toe out as required.....unless there is no toe in on the Dexter axles and they can be interchanged....Benny

[Roy in TO]

I may be wrong, but if you reverse the axel it will affect the built in toe in

Interesting Benny,

That might make a case for using Flexride axles in leading arm arrangements. They use cartridges inserted into the main axle tube. One could potentially swap L for R arms keeping the main axle oriented as it was fabricated. I don't know if the toe in would be correct since there is a potential difference in the effect of vector forces on the arms.

[Kevin K]

Dexter axle should be installed as trailing arm. Go with the 10 degree down angle. I installed the 22.5 degree down angle and its a little high.(13" Scamp)

[Roger H]

The main reason for installing a 22.5* axle now is to raise the frame to the "rv standard hitch ball height" of 18". Many of the older scamps had a hitch height of 14" which was fine when towing with the family's '75 Plymouth Valiant, but now the RV industry has pretty much settled on a hitch height of 18" (give or take). Most hitch receivers and draw bars are built to accomodate that height.

Roger

Here's a Ford Falcon towing an Airstream Falcon.

[Roy in TO]

but now the RV industry has pretty much settled on a hitch height of 18" (give or take).

I did a 4" lift while switching to trailing arm. That allowed the axle to clear the floor with it's built in alignment. I used zero degree axle and switched to a ST145R12. I'm pretty close to that 18" standard with a 1/2 loaded trailer.
(and no it has not been drinking)

[rudock1]

I may be wrong, but if you reverse the axel it will affect the built in toe in......the axel should have to be designed either for toe in or toe out as required.....unless there is no toe in on the Dexter axles and they can be interchanged....Benny

I'm in the same boat with an old leading arm axle. I had an email exchange with Dexter on the toe-in subject and a bit more about brakes:

Me:
Hello, I have a plan to replace a 23 year old #9 Torflex axle. My question is about toe angle (toe-in). Your Applications Manual gives a definition for Toe Angle. Does your current Torflex #9 or #10 have a toe angle built into the axle?

Dexter:
Thank you for visiting the Dexter Axle website and sending us your question.

The allowable toe for our Torflex axle product line is 0 degree toe out to .31 degree toe in per wheel end.

Me:
Thank you for the prompt and helpful response. Could I interpret the answer as that the Torflex axles are essentially "straight", but that a 0 to .31 degree toe-in is the acceptable manufacturing tolerance range?

Dexter:
The axle tube is bent UP in the center to set the camber of the axle. The axle tube is "straight" front to back. The allowable toe is controlled in manufacturing by the sub-assembly of the spindle/torsion arm/inner bar.

Me:
Thank you again. You and your company have first-class customer support (and products)!

As you might have guessed, my old Torflex axle uses the defunct leading arms orientation. Converting the trailer frame to use a modern trailing arm configuration would require a significant undertaking. My questions about toe-in are considering mounting a new axle, reversed to the old style leading arm orientation.

A couple more questions:

1. Can I specify in my order that the toe-in I want should be 0 degrees?
2. Can I specify in my order that the frame mount brackets be "swapped" so that the axle position in the bracket is in a better spot?
3. I'd really like to use 10" brakes, but the #9 Torflex is set for 7". The trailer weighs in at close to 2000 lbs. near the top of the #9 range. The #10 Torflex is probably too stiff just to get 10" brakes. Can the #10 be ordered with a lighter load range? Or can 10" bakes be mounted on a #9?

Dexter:
1. No, you are not able to request specific toe.
2. You can not specify that the brackets be oriented 180 degrees front to back without submitting a proposal to our Sales & Marketing department to agree to a special axle design and typically they will want some committment of volume for doing that type of "out of the norm" assembly.
3. You can actually specify either the 10" brake on the #9 as a "hybrid" (capacity limited to maximum of #9 series) OR you can order the #10 which comes "standard" with 10" brake but specify that the custom rubber capacity be tuned down to as low as 2300 pounds.

So.... I'm guessing that "0 degree toe out to .31 degree toe in per wheel end" sounds close to straight to me - less than a third of a degree "per wheel". So, flipped around the toe would be 0 degree toe-in to a maximum of .31 degree toe-out. Since I do not know about these things, is that potential .31 degree toe-out trouble?
.... your thoughts?

Billy

[jeff y]

reading your post got me thinking and very confused. more so by dexters response. most toe in/out is expressed in inches and you must convert to degrees to compare what dexter is telling you. that takes some trapezoidal geometry. i do alignments and am an ase master tech but i'm not 100 percent sure of it so i looked up a couple things. you need your wheel size (tire and wheel diameter total)to be exact but really you dont need to be that precise. on my scamp with a new axle (foward arms) and 185/80/13 (23 inches overall diameter) i came away with 1/32 toe out per side(about.087 degrees per side, total both sides 1/16 or.174 degrees) most alignment machines specify .5 degree tolerance which i tighten up to .25 to.175 depending on application so you are likely well within tolerances no matter which way you mount your axle. toe out is probably better than in but shouldent matter that much i think. toe out probably creats some drag and tracks better(think funnel out at top in at bottom). equal is the most important each side and centrifugal force pulls outward at speed anyway so .087 is really negligable. one good pothole could adjust it for you anyway. confusing enough?? unless you want 20 inch chrome spinners and dragster tires it'll likely work fine and the trailing arms ride smoother i'm told. good luck.
jeff

[Pete Dumbleton]

Get wheelbarrow, load it and try to 'push' it over brick. Then 'pull' it back over brick. First is leading arm, second is trailing arm -- There is indeed a difference.

[Ken J]

I just purchased a Perris Pacer - it needs an axle - like bad - it has not been used much over the years and has mostly sat - worst thing for rubber....

Anyway - I agree it would be better to use trailing arms - wheel barrow example is good - having said that - all these trailers were built with leading arms and its seems to work as they are on the road after many years.

Specific to the Pacer, there is very little framework forward of the axle, so it seems to my my only option is a leading arm axle....

So its seems to need to decide 10 or 21 degree angle - right now its in the negative territory.

Ken J.

[Kevin K]

My Scamp with 22 1/2 degree down trailing arm axle.



Before replacement

[Ken J]

That looks a lot better - yeah mines a "low rider" too - Scamp must have a different frame than the Pacer....

Ken J.

[jeff y]

kevin your 83 is a trailing arm axle? built that way or did you change the direction? it does make a huge difference in clearance and ride. is the floor lower all the way to the dinette or just in front of the door.
jeff

[Roy in TO]

That looks a lot better - yeah mines a "low rider" too - Scamp must have a different frame than the Pacer....

Ken J.

They are all different, but similar. Here's a cross section of mine. The grey is the original frame, the orange is what was added to convert to a trailing arm using 0 degree. If you want I can send you a full sized diagram so you can go out and measure for yourself and compare.





There is a full description of a scamp axle swap either here or on Yahoo scampers with pictures showing the frame. I've got a years worth of fixes to catch up on documenting and finish posting before I will get to how I installed mine last week.

Here's a link to the post here:
http://www.fiberglassrv.com/board/in...howtopic=28062

[Roy in TO]

Till I can post the entire fix, I will post two more pictures. One of the trailer post axle swap and the other of the streetside view of the metal addition. The rear is to your right in both.




You'll find before and interim pictures in a lot of my posts here on FGRV in other threads.

[Roy in TO]

I've tried to enhance the drawing a bit, hope this shows everything a little better.





BTW, Final hitch height is pretty close to 18" - I'll know the exact once we get it loaded for travel.

[Kevin K]

jeff y
Mine was a leading arm and I changed it over to a trailing arm . I used a Dexter #9 axle 22 1/2 down. My floor raises up by the dinette.
Dexter information
http://dexteraxle.com/i/u/1080235/f/6-8K%2...0-05_80_res.pdf
I bought mine from red trailer. Site http://www.redtrailers.com/ On my Scamp I had to add some rectangular steel

[Ken J]

Great pic! What I have now is just a 2" or so flat bar under that side of the trailer - I guess I could replace that with the bar that you show - hmmm major surgery....

With the trailer up higher like that, do you get any sway while towing?

Ken J

[jeff y]

thats real interesting kevin. i just replaced the axle with an original from scamp. looking now i kinda like the trailing arms better. not sure. did you run a cross beam linking your rail additions for rigidity? the box on the original frame seemed thin and i worried it might shift under the loads. was the replacement tube thicker? i posted some pics in mods section under "scamp gets an axle". it went right in and measured perfectly to track straight. did you have any trouble locating it front to rear or side to side? also did it change the weight proportioning front to rear and get any sway side to side at rear? im not sure if the dynamics of the axle pivot point change loading or is it the location of wheel center(bearing) that determines balance? i think it should be wheel center but your towing experiences before and after would really tell. thanks
jeff y.