Something funny about U-bolt tightening...

[Art-n-Marge]

Here's the scenario. Thanks to the MOC, I now know to check the U-bolt torque on the rig on a regular basis and the torque has been holding well.

A few days ago, I used 4x4 blocks and jack stands at the frame on the same side of the rig after using a bottlejack at the u-bolt to gain the lift to deploy the jack stands. Then I was free to spin the Monty tires to adjust the brakes and all looked good (a little adjustment was needed, but some was needed nevertheless). Then I removed the jacks from that side and did the other side. Nothing unusual at this point.

Now here's the curiosity. Just for grins after someone posted reminders about checking the nuts on U-bolts for proper torque, I figured it's been almost 6 months I may as well check them. So yesterday, I found most u-bolts nuts still holding the torque except for the ones that were used as a jacking point. Some of those needed some tightening but non-jacking U-bolts were 65 ft/lbs on the nose.

I'm guessing that in some cases the bottle jack pushing up on the U-bolt just might cause the U-bolt to seat up against the axle a little bit more and cause the nut to get a little loose. I do see that most U-bolts aren't always flush to the axle and there might be some gap however small. I went ahead and torqued them back to 65 ft/lbs (3 of 4 had this anomaly), but I was wondering if we should all remember to check the torque if the U-bolts were used as a jacking point.

Any thoughts? Extra concerns?

[exav8tr]

Art, They left the U bolts off mine. what do I do now??????

[8.1al]

Good observation Art

[Illini Trekker]

Good eye Art, 65 lb is not that much torque and I can see the jack helping seat the U bolts!

[H. John Kohl]

Art,
I do not jack on the AXLE even at the "U" bolts. The manual says DO NOT JACK ON THE AXLE. You are thinking the jack tightened the "U" bolt. I am thinking 3000 pounds to 6000 pounds may have bent the axle tubing and caused the "U" bolt to come loose. You have just given me another reason not to jack on an AXLE. Thanks. Good luck and let us know what you find.

[SlickWillie]

quote:Originally posted by H. John Kohl

Art,
I do not jack on the AXLE even at the "U" bolts. The manual says DO NOT JACK ON THE AXLE. You are thinking the jack tightened the "U" bolt. I am thinking 3000 pounds to 6000 pounds may have bent the axle tubing and caused the "U" bolt to come loose. You have just given me another reason not to jack on an AXLE. Thanks. Good luck and let us know what you find.

I saw a post where someone took their unit to the factory for service. The tech put the jack under the u-bolts and the owner questioned them. The tech told them that it was acceptable to use the u-bolts or the frame. I use the u-bolts myself. I suspect the "do not jack on the axle" is a liability issue. Jacks do have a tendency to slip off round surfaces if not placed properly.

[drknapp]

When I was doing our PDI I asked our dealer where it is recommended to jack the trailer and he told me at the axles. (probably not the first time a dealer has been wrong. :-) ) Where would the best place be?

[Art-n-Marge]

I've heard the best place to jack up the trailer is at the frame as close to the tire in question. I can see that this is the strongest place to do so. But on the Driver's side I have propane plumbing in the way and finding a place to jack up is tricky. The other corners are good, just tricky finding the frame because of the undercover and body panels.

The issue with the frame is that it is pretty high from the ground which means very tall jacks, jackstands and/or numerous blocks are needed. It also takes a long upwards travel distance to raise a wheel since when jacking from the frame, the frame has to raise quite a way before the suspension starts to raise the tire. I have all this stuff at home, but I don't like to carry all this weight and gear while on the road.

I now carry a set of 4x4 blocks and the bottle jack which are sufficient to raise from the frame and get the tire in the air. Prior to this, I have only had one emergency requiring to jack up a tire and used the U-bolt at that time. Now, with the blocks I won't even do that.

Phil (exav8tr), you can thank God you DON'T have to worry about this! You deserve to brag about that. They didn't leave the U-bolts off, they were nice enough to remove them as a potential problem!!! Let's just say you "paid" for the privilege.

[8.1al]

I have a dvd from Keystone on proper lug nut tightening and in the movie they have a jack on the ubolts. I questioned them on it and was told that was ok. Confusing isn't it? If I am home and doing maintenance I jack under the frame, if I am alongside the road changing a tire, I will use the axle. When using the frame you have to jack it up so high I wouldn't want to do it with traffic whizzing by blowing everything around

[skypilot]

Phil: Check the glove box - they probably put them in there as spares

Art: Good catch. I had to have my axles alligned and the shop actually built new U bolts saying the old ones were 'stretched'. Regardless, they mounted them flush with the spring and even then they jacked up on them to 'mate' them with the spring surface. Told me it made a longer lasting contact point to reduce future torque changes. Now just over a year and no problems with them.

[TLightning]

The manual says to place the jack under the frame near the spring hanger...NOT under the axle.

[Illini Trekker]

I use the u-bolt closer to the wheel has the wheel hub looks like it is pressed onto the axle. I would not use the inner u-bolt because that one looks like it has more give to it. To use the frame you should put the camper on the truck to take the weight off the front legs, also if you don't find the center of the frame the Ibeam could be rounded. I think picking the lesser weight at the inner u-bolt poses the less risk IMOP.

[pbahlin]

I've tightened mine 3 times in 3 mos. (65 lbs) and 2500 miles of towing.

Each time I find 3 or 4 that have loosened.

[Tom S.]

To try and raise one of these behemoths high enough to remove a wheel by lifting the frame is difficult, even with a 12 ton hydraulic jack, and potentially dangerous. But as several have noted, the manufacturer recommends you do not lift by the axle. So what to do? Use a large jack under the frame and lift it high enough to take the weight off the axle. NOTE: that does not mean you have to lift the tire off the ground! Now, put a smaller jack under the axle between or on the u-bolts and lift the wheel off the ground. This way, the only force on the axle is that of the spring, which is much less than the weight of the trailer.

[8e3k0]

You will not hurt the axle tube if the jack is centered properly under either u-bolt. That tube is minumum of a schedule 40 and is difficult to bend when the point of load is near the wheel. (The u-bolt adds to structural strength).
Jacking under the frame becomes very difficult and danderous because of the height required to relax the suspension. The reason the manufacture states not to do this is; someone will try and jack under the tube far away from the wheel and yes you can then bend or deflect that axle.

[Crossthread]

Just curious,does anyone know how far the spindel goes inside the axle tube? Bill

[Lambchop]

Yes, manufactures specifications are too vague at times. They print things that the owner should not do. Actually, most people do Not read the owners manual anyway. This is from experience in the auto & truck business.


Roy

[LonnieB]

Crossthread, most of the spindle shafts I have used go into the axle tube 8 to 10 inches, but I have seen them around 6 inches too. They DO go into the axle tube at least far enough past the U-Bolts to keep the axle tube from being crushed by the clamping effect of the U-Bolts.

I jack on the U-Bolts unless there is some reason, such as working on suspension components, when the weight needs to be off of the springs.

[Crossthread]

Thanks Lonnie,I too thought that they had to go past the u bolts. Bill