Fellow Sunline Campers
I know some of you may have been following my axle saga, well I have to report, all is good now. If any if you are having tire wearing problems, we might be able to help you check what to look for.
If you ever find your TT tires wearing tires at an accelerated rate, this post might help. It's long, but it ties axle alignment and installation all together. This is geared toward leaf spring suspension but some of the same alignment methods can apply to rubber torsion type axles.
Last fall I started a trouble shooting post and online research looking for anyone out there that has done TT axle alignment and posted about the details of doing it. I found a lot of bits and pieces but nothing that tied the whole thing together for a TT that is. There is a lot out there on semi trailers, just not a lot on TT’s in much detail. For those wanting more into the trouble shooting endeavors, see this post complete with a lot of pic’s
Tire Wear Pattern-Tandem Axle TT (Pic's) Where to look next
To keep the typing down I’ll try and do this mostly in pic’s so you can visualize better what I am talking about. Hopefully others who have done this before may see this post and can comment on easier methods to help others along. I’m not an alignment expert and if someone sees something not quite right, please point it out. I really had to dig to find this info readily available. However what I have now is light years ahead of where I was. And after 200 miles of towing, I still have not worn off the little rubber spikes on OD of my new tires. So I did some good and learned a lot about TT running gear that I never gave a thought to prior.
First I’ll make a few big picture statements.
1. Changing or aligning TT suspension is more then your average spring TT maintenance. This should only be attempted if you have the adequate equipment for the job and extreme caution exercised at all times. Working on machinery is inherently dangerous depending on what and how you are making repairs. What ever you do, it is totally at your own risk from anything you see here in my post. There may be a few tips that can be used to find out if you have a problem, then take your TT to a shop for repair. And then are those who are even more into this then I am. So have at it.
2. The words TT suspension, axle alignment, long lasting and the word “precision” are 4 sets of words that do not always go together. The unfortunate part is, with a little more care, following the axle manufacture guidelines, a few upgrades and axle adjusters, precision can be brought into most TT suspension setups’ easily and economically.
Now on with the show. First off my problem, burning up tires. I had one rear tire really grinding itself up in short order. This camper does not have a lot of miles on it. These pictures are of my tires with only approx 4,000 to 5,000 miles on them. How I bumped into this was my tires have aged out and I went looking for the tire size and, WOW these things are shot in less then 1 year from me owning the camper. I have put on about 2500 to 3,000 miles at the point of these pics and the prior owner rarely used the camper for long trips.
For compassion here is my spare tire, never yet used as seen by the little rubber spikes still sticking up. Nice and even in tread width and depth.
Now the best even wear. Left front.
And the worst wear, the left rear. Towing mileage about 4,000 miles did this.
Now the right side. Here the wear flipped. The Front is worse then rear and both have uneven wear.
I’m a firm believer in weighing the TT/TV combo many different ways and this TT is not close to full axle loads or GVWR, yet I have tire wear what I consider extreme wear. Here is a diagram of the basic wear pattern and axle weights.
Since the front left tire was wearing so even I thought that it was in alignment and the rest where off. Actually that front left was just that the front axle was so far off that it put the left front tire into alignment by coincidence.
The biggest problem I had was finding out what true alignment specs are for a TT. Once I found them, then the road to recovery was at least a straighter course. I knew where I had to end up. Here is what I found.
Axle alignment.
Front Axle: For tandem axle TT’s, the front axle is to pull true to the tow ball within +- 1/16” as measured from the ball to each wheel position. This insures that the front axle is towing straight behind the TV. If it is on an angle, the TT will steer to one side and can create what they call dog tracking going down the road.
Rear Axle: For tandem axle TT’s the rear axle is to follow the front axle within +- 1/16” of being parallel as measured at the wheel area. This insures that the rear axle is tracking in line with the front axle.
Note I used the wording “at the wheel area” I have found there is a lot of accumulated error in the components that actually are in the suspension. I my case, most times I used the machined surface of the brake drum as a datum point. Goal is to get that running surface in alignment.
See this sketch.
Also see here for a Dexter link
See page 19 of the down loadable Product Applications Manual.
Wheel Toe: Here different sources stated different things on what right is.
(source, Dexter tech service)
For Torflex axles: 0.00 degrees toe out to 0.31 degrees toe in
For leaf spring axles: 0.25 degrees toe out to 0.25 degrees toe in
(Source, Alko tech service)
For a loaded axle: 0.00 to 0.5 deg toe in.
(Source, trailer alignment shop)
For a loaded 5,200# axle toe angle: +- 1/32”
Axle camber Here different sources stated different things on what right is.
(source, Dexter tech service)
For 60 ksi tube axles: Unloaded axle measurements
For a 3,500# axle D35: 0.50 deg nominal. Min. 0.37 to Max 0.63 deg.
For a 4,400, 5,200, 6,000, 7000 and 7,200# axle: 0.90 deg nominal. Min 0.67 to Max 1.13 deg.
(Source, Alko tech service)
For a loaded 5,200# axle: 0.00 to 1 /2 degree. There should be no negative camber.
(Source, trailer alignment shop)
For a loaded 5,200# axle camber angle: 0.00 to 1.0 degrees.
So those where the spec’s I could round up. Now what I had. See here:
This is a text book case of just how messed up an alignment could get. Well almost, my camber was still at least positive and in range. However the axle alignment was way off and the toe was way out of range and in a heavy tow out condition. What caused this? From everything I can tell this much I know. The hangers on my frame are not true to the tow ball and they are not square to each other. Next the axle tubes themselves had the stub ends welded in wrong as there is no bend in the axle tube and the toe out is exactly equal on both ends. This all combined with large tolerance mounting methods used in TT manufacture sort of added up to the perfect storm to burn up tires by a high scrub angle with the road.
So now the recovery process. First was to rebuild the worn plastic nylon spring bushings and put in bronze bushings with grease fittings. This also included a heavy duty shackle upgrade and a Dexter EZ flex equalizer. See this post of mine of picture details on EZ flex post.
Dexter EZ Flex Equalizer Upgrade With Many Pic's
Here is the outcome of the bushing rebuild
Now that I had good tight bushings, I rechecked the axle alignment. Now it is even worse then before. The bushing play actually helped trick me as it slightly twisting the axles into better alignment then in a static state. Now I say better, but it was still out in left field and way out of spec. I was now able to confirm the original install was wrong starting with the hanger fit up and it escalated from there. So now what?
I started calling a few dealers if they aligned axles. The ones I called only changed them under warranty with new ones from the factory. So I called the factory. They only sell new axles and do not bend to align them. They did give me the name of the local axle distributor a few miles down the road who would sell me new axles. So I called them. Axle Inc in Elkhart IN. So after about 10 minutes I had 2 new 6,000# axle tubes on order that UPS would delver to my house. I had all my axle measurements already so I was good to go. After seeing the heavy toe out condition and the alignment issue, I really did not want a shop bending my original ones trying to fix all that problem. Axle tubes do not cost that much. I upgraded from 5,200# to 6,000# axles for only a little over $100 each plus freight. And I upgraded to the zerk greaseable axle ends for about $15 more an axle. Yes I needed to do the work, but for me, that is not a problem.
So here is the correction process.
Here is how the 2 new axles came to my house.
You can see here the grease hole that comes up just behind the inner bearing.
I also checked the unloaded axle camber before I got to far along. Used a 36” straight edge on center of the axle and measured the depth of the bend. Then used right angle trig to determine the axle camber angle.
Next comes jacking up the TT. Here caution needs to be exercised and you need heavy enough equipment. In my case I have 4, 6 ton jack stands holding up the 7,700# axle area of my camper. I use the larger jack stands for stability more then weight rating.
Tires off, TT on stands
I also use 4 bottle jacks under each axle seat area to keep the shackles from flopping down on me while I’m working on the axles. And I will need them for the alignment process later. I am not really lifting in this area, just supporting the roughly 100# of axle weight.
Next is to get the axles off the TT meaning dealing with rusted U bolts. Some just cut off the old, in my case I dressed up the threads a weekend or so before hand so on axle changing day I did not have to deal with frozen on U bolts. Start with lots of penetrating oil, soaking over night and then again fresh the next day. I also used a chaser die to clean up the threads first.
And a deep socket to run the die up with.
Now the threads are in usable condition. So out comes the breaker bar to break them loose. Oh, the kneeling pad helps the knees on my concrete….. I’m not as young as I use to be.
Now that I was past the U bolt issues, I leave one snugged up to hold everything in place as I take off the drums and back plate. You can drop the spring pivot bolts and take spring, axle and all out, but in my case it was easer for me to lift the tubes apart from the drums etc. And I did not want to be over working the new serrations of the spring bolts in the hangers I just installed a few weeks earlier by pressing them in the spring bolts again. So off with the axle nut.
Then the brake drum
And here is why you need to check your brakes often. A blown grease seal even on standard hand packed bearings. Since I bought this TT used, this is the 1st time I have had the drums off on all 4 wheels. Always use new seals when putting the drum on, they are cheap compared to this mess. The seal was nicked.
Now all that is left is the axle tube. Not that heavy.
And now no axle
And no axles at all.
The old next to the new
I check the toe on each axle before installing. Here is the setup. I put just the brake drum on each end of the new axle and place a 18” scale on the drum machined surface.
The use a tape measure and check each end.
Rear
Front
As you can see, on this axle there is a total of 1/32” toe in as measure at 9” from center. Doing some math that comes out to 0.10 degrees toe in. The other axle was 0.00 deg toe in. So I’m good to go.
Next I made axle adjusters so I can dial the final alignment dead on. This was an evolution as I made them for my 5,200# axles thinking I would reuse them. They started like this.
However my 6,000# axles, the axle seat was made different. So I had to change the approach. This is what I ended up with.
That last step was very important that the adjuster is dead flat against the axle seat. Slot the axle seat for the adjusting pin as needed so there is no air space between the axle seat and adjuster when you tighten up the U bolts. If not the spring pack will not be properly compressed.
Now to the next post. The assembly.
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