trailer axles

The concept of tandem axles in a turn has been explained very well. If you think you have strain with tandem axles in a tight turn, think about what happens with triple axles. In fact, some rubber torsion axle manufacturers don't recommend even using those axles in a triple axle configuration.

Misc. pics - distortion in lower beam flange, spring hangers bent sideways from lateral force applied to TT, wheels out of camber by lateral force applied to TT, separated weld in aluminum framing of superstructure (from frame movement). Last photo is right angle turn in a CG. The plastic spring bushings in this TT were all totally shot in just over 2K miles from new (due to continual spring hanger movement). When the trailer was on a hoist, the spring hangers all bent sideways in one direction and when back on the ground, they all bent in the opposite direction - and this was without any lateral force applied. This is a fabricated/welded 3-piece beam. This frame is a failure waiting to happen. This frame is used on many ultra-lites.

I will also say that this is the reason that I try to avoid making turns that are any sharper than necessary. The greater the radius of the turn, the less the lateral drag.

NCMODELA wrote:
Hi, I have a 2011 keystone summerland. I have noticed that when I go around curves like a coldest that the front and rear axles are not aligned. They have a different camber. But after driving in a straight line they shore back up. There is no irregular wear on the tires. Is this what they mean by floating axles?

Thanks bill

Yes it's normal. Also when backing in, and turning sharply you will see the tandem out of line. It is best to always back far enough to be able to pull up, and straighten them out.

But that is why trailer tires are built differently tan TV tires. They are designed to slide sideways in a turn, and not pull off the rim

True that. Small world, I have a 2001 BMW 530i.

You are lucky to have a box frame. I don't think there's many around anymore on TTs. Vintage stuff can often be much better. My old BMW 2002 was built like a tank - they just don't built cars like that anymore.

When we bought our first TT, I thought all you did was hook up, drive off, and go camping happily ever after. Not the case as it turns out, lol! So many things that can happen, things you need to maintain, not to mention the things you end up learning that you thought you never would.

westend wrote:
Gil,
Just one more reason I appreciate my vintage rig more. I have torsion axles with shock absorbers mounted on a full box frame. The frame is a straight as the day it was made. The Hilton tracks as straight as an arrow and I can park without stab jacks and be comfortable, there is very little movement. I haven't really looked at what the axles do around a tight corner but I bet the tires are taking most of the sideways "scrub".

Gil,
Just one more reason I appreciate my vintage rig more. I have torsion axles with shock absorbers mounted on a full box frame. The frame is a straight as the day it was made. The Hilton tracks as straight as an arrow and I can park without stab jacks and be comfortable, there is very little movement. I haven't really looked at what the axles do around a tight corner but I bet the tires are taking most of the sideways "scrub".

This is my take on this phenomena.

It may be kind of "normal" in the sense that it does happen a lot, but IMO it's not good. When you go around a corner, each axle has a different turning radius. One axle and set of tires will literally be dragged sideways across the pavement. If the tires go out of camber, it's because something is bending, and when steel is forced to bend all the time, that is definitely not good.

When this happens, the bottom of the spring hangers get forced sideways. If you have over-slung axles and the taller 6" spring hangers, the effect is worsened due to increased leverage. The axle tubes are paper thin and they will flex. With continual flexing of the spring hangers side to side over time, the vertical web of the I-beam will be forced to flex and will eventually develop fatigue cracks. If you have a lite-weight TT with the I-beams fabricated from 3 pieces of mild sheet steel and look like a normal I-beam, these are very susceptible to developing cracks. Often, the cross-bracing between the I-beams does not have gussets. If you look at photos of frame cracks, you will see that the cracks (which run lengthwise) are right where the cross-bracing is attached behind the I-beam. This point becomes a pivot point.

If you see this happening, first inspect the I-beams immediately above the I-beams for signs of cracks. Then you can consider strengthening the frame. Cross-bracing between the bottom of the left and right spring hangers will help. Mor/Ryde makes them or you can make your own.

Gussets welded onto the side of the beams above the hangers helps. A length of 2x2 welded to the underside of the I-beams between the hangers helps. Some frames come from the factory this way, while many have no additional bracing or stiffening at all.

You can take a straight-edge and put it on top of the lower I-beam flanges above the hangers. If your hangers have been flexing a lot, you will find the I-beams are distorted.

When you are towing your TT, does the tail end seem to bob up and down a lot? That can be a sign of vertical flex in the I-beams. The longer a TT is, the more this can potentially happen, especially with the "fabricated" I-beams. If this happens, it will transfer movement to the TT superstructure and even cause damage to aluminum framing. Adding shock absorbers to tame the vertical movement would help minimize any potential damage to the superstructure.

If your TT seems to have a lot of "bounce" when set up with the stab. jacks down, that can be another sign of a flexing frame.

Lite-weight TTs can often be close to the GVWR when all loaded up. Sometimes you can end up overloaded simply by towing with one full holding tank. Overloading of course puts even more stress on a frame.

If you do indeed have excessive spring hanger movement, it is hard on the spring bushings and they can fail prematurely, and in some cases, fairly quickly.

Not only can frame cracks happen, I suspect that over many miles of towing, the hangers will move sideways even while driving in a straight line due to the weight of the TT moving side to side, creating a sideways lateral force on the hangers. The result can be increased tire wear. To the best of my knowledge, nobody out there has studied this - tire professionals or TT owners. The more a person can do to minimize hanger movement, the longer your frame and tires will last.

If you do some googling for TT frame cracks, you will find that they typically crack just above the spring hangers. What I described above is why. The frame manufacturers simply build the lightest and cheapest frames they can unless a savvy TT manufacturer specifies something better. If you are still under warranty on a TT and nhave frame problems and you try to make a warranty claim, often the frame manufacturer will simply tell you that you must have overloaded your frame and it's your fault. Some are completely unaware of what's going on until something breaks or prematurely wears out (tires, eg.) and then they say "what the @#$%".

Yes - it is odd to see the first time, but it is perfectly normal. The 'pivot point' for the trailer is actually between the two tires. For this reason, they have to move opposite directions in a turn. The sharper the turn, the more severe the effect.