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Old 05-22-2023, 03:40 PM   #1
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Axle alignment

Can anyone tell me how critical axle alignment is?
(Please see corrections to measurements in following post)
Measuring the distance between two axles on my 2007 2499, I'm finding that the right side is 5/8" further apart than the left side. Measuring from the hitch back to the front axle I get a 1/8" longer distance to the front axle on the right side, so it seems that the front axle needs to move forward 1/8" on the right and the rear axle needs to go forward 3/4" on the right if I have that correct.
I just replaced all four springs, but how they get so far off is a mystery to me since there is a locating pin on the spring that goes into a hole on the plate which doesn't allow for much fore and aft movement.
Thanks,
Rich
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Old 05-22-2023, 03:59 PM   #2
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Sorry for the confusion, I wrote that wrong. The LEFT side axles are 5/8" further apart than the right. So I'm thinking that the front axle needs to move forward 1/8" on the right and the rear axle needs to move 1/2" further to the rear on the right.
Rich
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Old 05-23-2023, 08:11 AM   #3
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Hi Rich,

The numbers you have posted are not good. If the places you have taken the dimensions from are correct, they are really bad, and you will wear tires at an accelerated rate.

First, let's sort out how "exactly" you took them. There can be a lot of errors in the wheel alignment measurement depending on how and where you took them from. Tell us how and where you took the measurements. Pics help greatly.

The short version of this per Dexter's recommended spec I have shown in this sketch



This post has a lot more detail, and there is a link to a prior investigation post where I had to sort out the causes of bad wheel alignment.
https://www.sunlineclub.com/forums/f...ics-10043.html

Here are some things to help sort out how you ended up where you are now.

1. First, do you "still" have each tire where it came off the camper in the known mounting location before the spring change? We can use the tire wear pattern to back into how good or bad the alignment was before the spring change. But you must know which tire came from which location and, ideally, a good number of miles on the tires.

2. Can you estimate how many miles are on the tires before the spring change?

3. New springs can be made differently than your old ones. Do you still have the old ones and know which spring came from which location? We have had a member report with documented numbers that they had flipped the springs around, and the alignment came back in spec. But they were not out as far as you are and were still on the original springs.

Read this over and come back with more info on how exactly you measured the system.

Hope this helps,

John
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Old 05-24-2023, 04:28 PM   #4
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Hi John,
Thanks for all that help. I'm pretty sure the tires are back in the same place because I have tire pressure monitors and I don't think I had to move any of them when I remounted the tires on the axles. Bad memory these days. But regardless, the old springs may have been aligned well (I had installed the axle flip kit 5 or so years ago) because I don't see that the tires are wearing abnormally. They've been on the camper maybe a year, year and a half. The thing is, now they probably will wear faster with the axles out of alignment.

I still have one of the old springs and I have another new set due to a shipping mix-up (long story). So today, after reading your reply and post on axle installation, I decided to measure to see if maybe there was a long side and a short side. I measured the Chinese made new springs (not the ones I installed) and found that one side on all four was about 1/16 or so shorter than the other. That's not enough to be in the design, I figure just a manufacturing discrepancy. I also measured the old spring I took off and found no difference from the center out to the spring eyes. Now, I want to remove the wheels and measure the new springs that are on there.

The reason I changed them was because one had broken and I figured after 16 years, another one won't be far behind. I also installed new U bolts and nuts after reading about doing that. Now, I'm a little concerned about loosening and re-torqueing the U bolt nuts to move the axle where needed, but I think it needs to be done.

The measurements I took were done by rolling straight into a parking lot on level concrete and measuring from the back of the hitch jack tube to the tires. Not terribly accurate, but I wanted to get an idea of what was going on. I had already measured the distance between the axle tubes to find that they were closer to each other on the right side than the left by 5/8". When I have the wheels off again, I hope to be able to measure more accurately.
BTW, I tried to email you before I did the spring change, did you change your email address?
Thanks,
Rich
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Old 05-24-2023, 11:26 PM   #5
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Hi Rich,

A few things, I'm assuming when you did the axle flip, you changed the spring center bolt around so the round pilot on the end of the center bolt would be in the spring Ubolt mounting plate. Is this correct?

When assembled, some areas can add up against you when setting the axles.

Spring center bolt pilot to U bolt plate. Commonly, the hole in the U bolt plate is larger than the pilot pin of the spring pack. I have seen on some springs the gap in the U bolt plates was 1/8" larger than the pilot bolt. That means one axle could be up to 1/16" moved from the center if you pushed it to the extreme. And if the other axle on the same side of the camper was made to the extreme in the opposite direction, 1/16", then the two axles can be 1/8" apart. This can be 1/8" of your 5/8" problem.

If the spring is made not central from the spring eye in the hanger to the center bolt by 1/16" short, this shifts the axle center 1/16" close to the hanger. If, by chance, you install the front spring, 1/16" short, and the rear spring, 1/16" short to the hanger, then this adds up to 1/8" longer between the 2 axles. This 1/8" wider spacing plus the 1/8" from the center bolts can create 1/4" of your 5/8" problem.

Springs flatten under load, and the flatter spring will change the distance from the center bolt to the spring eye in the hanger. If one side of the camper is heavier by an "amount," that side will be flatter than the other side. The less flat side will have more distance between the two axles than the heavier side. Here again, if the flatter spring creates a 1/16" difference in each spring, then there is another 1/8" wider on the lighter side of the camper. If 1/8" added up against you, adding this to the error above, you may have found 3/8" of the 5/8" problem.

And then, there is the placement of the hangers and how they are welded to the frame. 1/16" is common weld tolerance. If one side of the camper has the front and rear hanger spring pin holes 1/8" wider than the other side, here is another 1/8", which, if it adds up against you, that can now be 1/2" of your 5/8" problem.

Here are some things to check before you jack the camper back up to change things.

With the camper tires on and the camper on the ground (a hard flat level surface) and the camper leveled out, measure from the top of the axle tube to the bottom of the frame and record each wheel location. Like this


By comparing those numbers, you can see which springs might have more load creating a flatter spring. From here, at least, you know if there is any difference between the left and right sides.

When you assemble the springs, flip the eyes to make the error in the center bolt to the spring eye on the front or rear hanger in your favor and not against you for the center distance between the axles.

When you tighten up the U bolts, pull the axle in your favor to help reduce the center distance. I use ratchet straps positioned as needed to pull the play out in the direction that is in your favor before tightening the U bolts. Like this


Tire wear, If you can accurately measure the tread depth across the face of your 1.5-year-old tires, you can see how they have been wearing on the old setup. By the naked eye, looks good, which can mean you cannot see by uneven eye wear, and it is good "enough", but you are not seeing gross wear. Unless you do cross country, most tires age out before they wear out if the wheel alignment is tolerable. And since you did not see gross wear on your old setup, whatever was there in alignment was OK. By odd chance, do you have dimensional data on the old setup before you took it apart?

While the Dexter spec is +/- 1/16" between axles, from what I have seen, you can run somewhat further out from that can get tolerable wear. 1/8" - 3/16"
difference loaded with weight, will have a slight level of wear and be in the group of they age out before they wear out. When you get into the 1/2" and up differences, you get gross to wear in about 3 years. It does not seem linear; there is a point where tolerable wear changes to gross wear, and I have not yet found that point.

Unless you measure it with a tread depth tool of sorts, you usually cannot see low-level wear that will show up in the numbers. But you can with a depth gauge of sorts. I used a caliper depth gauge. There is still a small error still in this, but it is accurate enough. See here,




This is what I call gross wear at 1/2" out of position


This is what in Dexter spec looks like after 2,500 miles; it is really good.


Here are all four tires after my alignment. I had an adjustable axle seat to dial that in that well.


You want to keep an eye on the tow ball to the front axle; if that is off a lot, the front tires take that hit for wear. The rear tires take that hit on wear with the spacing front to the back axle. You really need to reduce that 5/8" problem.

On your new eyebolts, as long as you have not towed much with them, loosening them up, correcting spring positions and then retorquing in an X pattern would be OK from my view. And do retorque checks on the U bolts after you start towing. 100, then 200, then 300 miles, then 500-600 miles would be prudent.

hope this helps and let us know how it goes.

John
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Old 05-25-2023, 06:22 AM   #6
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Hi John,
I'm up against a time crunch because we're heading out for the month of June to Maryland, buttonwood, then the adirondacks, Moffitt beach. So, I have to do the best I can to get it reasonably straightened out.
When you mentioned flipping the pilot bolt, are you saying that the center bolt that holds the spring leaves together was to be removed and reinstalled the opposite way? I didn't see that mentioned in Dexter's instructions.

I'll take measurements like you spelled out. Its parked on a level gravel pad right now, I wont have time to move it to a level concrete surface. I like your ratchet strap method. I'll also check tread depths.

Thanks for all of your help,
Rich
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Old 05-25-2023, 08:58 AM   #7
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Quote:
Originally Posted by vcrt View Post
When you mentioned flipping the pilot bolt, are you saying that the center bolt that holds the spring leaves together was to be removed and reinstalled the opposite way? I didn't see that mentioned in Dexter's instructions.
Hi Rich,

Yes, when you do the axle flip (over/ under), the spring center bolt should be turned over as well, so the round pin end is what is going into the new axle seat. The pin nut would then be up and in the U bolt plate.

If your spring pin is 3/8"-24 fine thread, go with 50 ft. lb of torque on dry threads (not lubed) on the spring pin.

This has come up before. Dexter did not mention this in their instructions, but not flipping the pin means the hex bolt nut is doing the axle seat piloting, which is incorrect.

See here for more discussion on this spring pin being turned over if you have time to read it.
It starts here, https://www.sunlineclub.com/forums/f...tml#post157965

And is mentioned here with the torque on the size of the pin.
https://www.sunlineclub.com/forums/f...tml#post158190

If the concrete surface is not level on measuring the axle to the frame, adjust the tongue jack to make the camper frame parallel to the concrete, assuming the concrete is straight, just not level. The objective is to have the axles loaded close to what you do when you tow down the road. Not nose-high or nose-low, as that can change the spring loading depending on which way the camper nose is.

Good luck and happy camping.
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Old 05-25-2023, 12:16 PM   #8
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I checked the axle to frame measurements and found a difference, then I realized since it's on gravel and there are some high and low spots, the wheels are at different heights, so those measurements won't be meaningful.
I need to set aside some serious time to sort this out after I get through other things I'm working on, probably tomorrow.
Thanks,
Rich
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Old 05-29-2023, 06:53 AM   #9
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I wanted to post a conclusion to this thread. With a lot of help from JohnB, I was able to take measurements from the hitch to the front axle, finding it to be in alignment, but the rear was the problem because it was closer to the front axle on the right side than on the left. Measuring the springs from the center bolt to the spring eyes, I found that the right rear spring bolt was not centered like the right front was, so I turned the rear spring around. Then, with the u bolts loosened up, used ratchet straps to pull the left side forward and the right side rearward. Oh, almost forgot, John's advice was to flip the center bolt on these rear springs because the round head is a smaller diameter than the nut, which gives more movement within the axle mount hole. With tension on the ratchet straps, torqued all u bolt nuts to 60 ft. lbs. (Dexter recommends 45-70 ft. lbs. for 7/16" u bolts). Now, I'm getting a closer measurement front axle to rear, but the gravel ground isn't totally flat as would be concrete or asphalt, so I need to recheck once I can tow to a flat, hard surface.
Thanks John!
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Old 05-30-2023, 11:34 PM   #10
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Hi Rich,

You are very welcome. Glad you made the situation better.

Here is how you can check if your rear axle may have bent along the way when you can. A high curb or a bad pothole may have happened some time ago, and you not realize it.

This is one way to do a "quick" check. There is more to this if the numbers come up bad, but if they come up good, then you have good odds the axle is not bent out of alignment.

1. On a hard, smooth surface, tow the camper straight, about 75 feet, and stop. You do not want to be in any part of a turn when measuring, as the axles flex in turns.

2. Facing each tire, find the tire's center and mark off at the 3:00 & 9:00 locations. Use a level if needed. Make a mark on the side of the tire by the tread area. Chalk, if you have it works, or even a piece of painter's or masking tape and draw a line on the tape.

3. Let's start with the front axle, the 3:00 location, on the left side of the camper. This would be the camper's back side of the tire on the left side. Using a tape measure and some duct tape, locate a tire tread and place the end of the measure clip "tight" deep into the tread face at 3:00. Find a crisp tread feature, and the measure will rest on the high spot. Get a good image of that location, as you will look for that same spot on the opposite tire on that axle. Duct tape the measuring end in place.

Looks like this


4. Pull the tape measure tight to the camper's other side (right side) and line up the tape measure with the same tread spot you picked for step 3. Since you went to the other side of the camper, you will measure at the 9:00 location straight across to the back side on the same axle.

Looks like this


Pull tight and read the number at the 9:00 location. Write down the number. Try and get the dimensions in 1/32" increments.


5. Now, do the front side of the front axle using the same method in steps 1 - 4. Record the distance.

6. Repeat the process for the rear axle.

Compare the numbers on each axle for the same axle's front and rear tread distances. What you are looking for is the toe angle of the wheels about the axle tube.

A. If both front and rear tread distances are the same axle, this is a 0-degree toe angle of the wheel on that axle. A good tire wear condition.

B. If the front tread distance is greater than the rear tread distance, this is a toe-out angle of the wheel on that axle. A slight toe-out is OK.

C. If the front tread distance is less than the rear tread distance, this is a toe-in angle of the wheel on that axle. A slight toe-in is OK.

Then compare the front axle to the rear axle. If one axle spindle is bent, it will create a more significant difference between them in either a toe-in or tow-out condition. In your case, your front tires were wearing acceptable. Ideally, the rear axle measures out close to the front.

The above is a quick "big picture" way to find a bent axle. It gets more involved with math and measuring to determine if the toe angle is in or out of spec. and which axle stub is bent. Or if both are bent. We can drill deeper into this as needed if there are larger differences between the front and rear axles.

Hope this helps

John
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Old 05-31-2023, 06:17 AM   #11
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We'll be heading out on Tuesday, so I'll pull over and check that. Will also crawl underneath to re-check u bolt torque.

I'm also putting up a post on awnings, look at that.

Thanks,
Rich
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Old 06-01-2023, 01:33 PM   #12
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Out of spec alignment can put more side force on the tire structure. This along with the normal "Interply Shear" found on multi-axle trailers can lead to belt separations and even a blowout.
Car alignment specs are usually in the +/- 1/8" range or less if you want o know the range.
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