Passport Axle Alignment

[Flyguy]

Wheel alignment is something that the RV owner seldom thinks about after buying a new RV until the tires start to show unusual wear after a short period of time. Some suspensions have adjustments on them to correct for things such as “Caster, Camber, and Toe-in”, my RV does not, I have a spring suspension system that is common on many RV’s today, there’s an arch in the axle that I can see that points up and I suppose that it allows for the trailer load so that the wheels remain flat to the road when towing, all the settings for caster, camber, and toe-in, are contained in the "factory bent axle tube and welded end plates", anyway all that I can see that I can do is to reposition the axles on their spring attachments so that they are perpendicular to the centerline of the trailer. Figure 1 shows the tolerances that I think I will have to deal with to get the axles lined up.



Upon the initial inspection I found that the two axles are NOT parallel to each other, measuring between wheel hub centers (measurement C), one side measures 14” and the other side measures 14 ½” and that’s certainly out of tolerance. The Passport series has a “spread axle” type of design so the distance between axles is greater than most trailers, the up side to this design is better load distribution, but the down side is increased tire wear due to a greater arc that the rear axle has to make especially in a sharp turn and this may explain why the rear axle isn't parallel to the front axle anymore (just a thought). The initial plan is to take the measurements as indicated in figure 1 and then shift the axles on their spring mountings so that they are within the tolerances as listed by loosening the U bolts on one side of one axle at a time and hit it with a small sledge hammer until it slides into tolerance then tighten the U-bolts in a cross pattern (X type pattern) and retorque to the following specs: ½” bolts = 55-60 ft-lbs, 9/16” bolts = 65-70 ft-lbs. First I need to measure from the tongue jack post to each side of the forward axle (measurement A) and get it straight and then set the rear axle parallel to it, anyway that’s the plan, and I will let you know how it works out.

[Flyguy]

My axles have slipped and rotated on their U bolt seats probably due to normal braking, when you apply the brakes the resistance of the tires on the road causes a torque force on the axle tube which is held in check by the U-bolts if they have the proper torque on the nuts. I have never checked the torque on the U bolts since the trailer was new and I guess this is my fault for not doing that, here's the info from my Dexter axle manual that came with my trailer:



I need to take the time to read my manuals. Also please note that the shackle bolts, spring eye bolts and equilizer bolts are only tightened to a snug fit as per the manual on page 59, the complete manual is on my homepage in the towing folder under Dexter Axle 600-8000lbs.

[Flyguy]

Well, after crawling around under my trailer I have to say that what I thought about the Dexter axles rotating was wrong, the axle spring seats are welded to the axle tube so there is no way that the tube could rotate under braking in their U bolts. One thing is clear though, the camber bend in the axle tube is not there anymore and this could be caused by overloading the trailer (though I don't think that this is the case), what I think is the case is that the axle rating is not great enough for the expected load, I would have liked to see 3500lb axles used. I found the stamping on the axle tubes and they say "2800lbs", now my trailers GVW is 6040lbs minus the tongue weight of about 600lbs leaves about 5440lbs to be carried by the axles and 2800 X 2 = 5600lbs total load carrying capacity for the axles. I figure that my fully loaded trailer ready to go is about 5600lbs, the trailers empty weight is about 4580lbs, at 5600lbs my tongue weight is about 575lbs, so 5600 - 575 = 5025lbs to be carried by the axles, this should not over tax the axles but somehow it evidently did at some time, anyway I am not equipped to rebend the axle tubes so I guess I need to talk to the local frame alignment shop here in town as I'm sure that they have all the tools need to do the job. At some time in the future I would like to just replace both axles with some other system, I have talked to MorRyde in Indianna and they gave me a price of $2000 to replace the spring suspension system with their rubber ride IS system and I'm considering that option. I'll let you know how everything turns out.

[Flyguy]

Here's the manual for the IS system: http://eaa1358.com/Passport/Disk%20B...S%20MANUAL.pdf and here's an animation in color of how it works: http://eaa1358.com/Passport/Disk%20B...suspension.swf click on the play button to see it in action.

[Flyguy]

Well I deceided to go with two new 3500# brake axles, I got a good price from a manufacturer in GA ($140 each), these are new and complete with new brakes and hubs and even comes with the EZ-lube type bearings. The new axles should be here by 5 July and it won't take long to replace the axles. I will try to remember to take pictures and post. For those of you with Passport TT's you will find the axle rating stamped on the axle tubes to see what Keystone installed in your TT, hopefully it will say 3500#'s.

[GBHRPS]

I'm thinking that I need to take a closer look at my setup, although the tires on my 5er show nothing but normal wear.

Fascinating! Please keep us posted!

[Flyguy]

If your tires are wearing ok then your probably ok, if you look under the trailer from the rear at the axles you should see an upward bend to the center when the trailer is unloaded (assuming that you have a spring suspension system) and this cranks the wheels inward at the point where the tires meet the road so that when the trailer is loaded the tires sit flat and square on the road, on my trailer that upward bend is gone when unloaded and bends down when loaded, I think that Keystone must have put the wrong axles on it at the factory or the temper of the axle steel was not what it was meant to be, either way these axles are toast and will be gone in a week or two.

[Terrydactile]

Originally Posted by Flyguy

Well I deceided to go with two new 3500# brake axles, I got a good price from a manufacturer in GA ($140 each), these are new and complete with new brakes and hubs and even comes with the EZ-lube type bearings. The new axles should be here by 5 July and it won't take long to replace the axles. I will try to remember to take pictures and post. For those of you with Passport TT's you will find the axle rating stamped on the axle tubes to see what Keystone installed in your TT, hopefully it will say 3500#'s.

The axles on my Passport are 2800# just barely heavy enough for the advertised loaded weight. So far the tubes are still arched up in the middle and the alignment to each other and to the hitch is still within spec. Hopefully all will stay put. I did upgrade the brake wiring to 10 gage and wow, what a difference.

[Flyguy]

Terry, tell me more about the upgrade in wiring to #10 wire, did you rewire from the brakes through the axle tubes and through the under belly cover all the way to the hitch? This answers the question "did Keystone put 2800# axles on by mistake", not likely since we both have the same axles, it could be that the temper in the steel on mine was not what it was suppsed to be.

[Terrydactile]

Originally Posted by Flyguy

Terry, tell me more about the upgrade in wiring to #10 wire, did you rewire from the brakes through the axle tubes and through the under belly cover all the way to the hitch? This answers the question "did Keystone put 2800# axles on by mistake", not likely since we both have the same axles, it could be that the temper in the steel on mine was not what it was suppsed to be.

Your axles were not a mistake, thats what they use. If you do some figuring you'll find that if tongue weight is not taken away from the weight capacity rating and you are loaded to max weight allowed the axles are not big enough without subtracting tongue weight. For instance 2800 X 2 = 5600lbs max axle rating for both but the trailer fully loaded can weigh max 6040. 6040 is already heavier the the axle rating. 6040 - 5600 = 440lbs. Guess what they say the advertised tongue weight is, 440lbs. They got it figured down to a frog hair with no room to spare.

I had heard and read discussions on the brake wire size used throughout the TT industry being undersize and in some cases several pieces twisted together like they were using up the scrap pieces. Undersized wiring in a brake circuit can mean a voltage drop over the run. I was at the time having some braking issues so based on forum discussions about the brake wiring I decided to take a look at mine expecting to find a loose connection some where. Didn't find it but I did notice that the wiring they used was grossly undersized according to Dexter's wire sizing chart. Keystone used what looked like #16 gage wire. It might have been #14 but I knew it was smaller than the required minimum size stated by Dexter for my/our TT's. Dexter reccomends #12 for 4 brakes up to 30 feet from the hitch. In fact Dexter doesn't reccomend using any wire size less than #12 for any brake set up even on single axle installation. I used #10 because thats what I had, but at any rate for your Passport it should be a min of #12. Its probaly undersize. Before I started I could only get about 6 volts back at the magnet at full power, after the rewire I get about 11 volts. Quite a difference and a noticable difference in braking.

So I replaced all the wiring from the junction box at the front (behind the battery) all the way to each pigtail coming out of the magnets. The wiring on mine runs down the curbside just inside the I-beam and up inside the underbelly plastic. I just pulled down that one side enough to work with the wiring. On a side note: If you pull down your underbelly covering enough to look in there you are going to be amazed at how all the wiring is just laying there on the plastic and on frame members. Its terrible. One of these days I'm gonna pull it all off and run the wires in a better way. After seeing this, I can understand why they use they underbelly covering. Its cheaper and faster to assemble if you don't tie up and run the wiring neatly. Then they use the underbelly covering as a selling point. I say if it wasn't there they couldn't sell them like that. Take a look, you'll see what I mean. I also ran the new wiring outside of the axle tubes but behind them to offer some protection from road debris. I reccomend that you upgrade the wiring if it is undersize when you replace your axles. Its very easy to do.

Hope this helps.

[Flyguy]

Thanks for the info Terry, I'll check to see what gauge of wire they used on my trailer. If your axles are still looking good then mine must have been a bad temper or hardness on my axle tubes, I've seen that on other things before, anyway I'll feel better knowing that the axles are rated for 7000#'s instead of 5600#'s, it seems that 3500 is more of a standard than 2800, I've looked through the Dexter catalog for spare parts and 2800# axles are hard to find, must have been a special order for Keystone.

[Flyguy]

Got the axles changed out today, this first picture (1678) was when we were ready to back into the garage, next pic (1681) we're in position to jack up the trailer, 1682 is a pic of the new 3500# axles, 1684 is jacking up the trailer, 1688 is the removal of the shackle bolts after placing jack support on the axle the shackle bolts were hard to remove and even harder to install, 1690 the rear axle is out, 1691 the new rear axle is in, 1692 & 1693 is the reinstalling of the shackle bolts, 1695 the front axle is coming out, 1697 is a shot of the old axles, 1698 is the new axle in front, 1699 is installing the last shackle bolt which did not want to be installed (it's always the last one that gives you the most trouble) but we got it! Everything works fine and it rides nice.

[Flyguy]

Continued:

[Flyguy]

Here are the final pictures:

[THedges]

I believe I have a undersized axle problem. Same issue that you had my axles combined with tongue weight are just at the GVW. I'm getting bad inside tire wear on the back axle. I have 3500 lb axles and I'm thinking about going with 5200 lb axles. The problem with this is, along with everything else, I will have to change out all 6 wheels ( I carry 2 spares), to 6 hole wheels.

Now that you have had the new axles for awhile are you glad you changed them out?

Thanks