Sway questions

On a recent trip with my TM 3225 I noticed at 65-70 mph I had a bit of side to side swaying. It seemed to go away if I went a little faster or slower. I use a reese friction bar so it stayed in control but was enough to make me a little uncomfortable. I tow with a chevy suburban. Is this due to the way I packed the TM? Should I put more air in the tires than suggested when packed?

To answer your question, most sway is usually due to not enough weight on the tongue (i.e. too much weight to the rear) or poor trailer design.  Since TM carefully designs to eliminate sway, try redistributing the weight in the trailer to cure the problem.

I don't recommend adding any more than the max pressure listed on the tire sidewall (usually ~50psi).  Be sure to check tire pressure when cold, as the pressure will increases with use (heat).

As a caution:  There is no danger using a sway controller on a trailer that has no sway problems.... many people on this board do this.  (I have one but have never installed it)  However using a sway controller on a trailer that has a true sway problem can make matters even worse.  Sway controllers often mask symptoms (not cure them) until the sway gets out of control.

[Bill]

By accident, I discovered another cause of sway - fortunately before it resulted in a real accident. At the beginning of a long trip, I loaded several hundred pounds of stuff in the back of my Explorer - way back, so it would be easy to access on the road. Result? Immediate sway problems - and I had never had a sway problem before. I stopped beside the road, folded the rear seats down, moved everything forward as far as possible, rearranging the load to move the heaviest items furthest forward. Result? The tendency to sway completely disappeared.

I imagine that the tendency to sway depends, in part, on the lateral stiffness of the tow vehicle's rear suspension. You didn't mention what year/style of Suburban you have, but as SUVs evolve toward increased creature comfort, and away from their earlier workhouse image, it seems to me that we may see more of this sort of thing. Some vehicles used to have (optional) sway bars to stiffen the rear suspension and reduce sway. Do they still?

Bill

[Denny_A]

By accident, I discovered another cause of sway - fortunately before it resulted in a real accident. At the beginning of a long trip, I loaded several hundred pounds of stuff in the back of my Explorer - way back, so it would be easy to access on the road. Result? Immediate sway problems - and I had never had a sway problem before. I stopped beside the road, folded the rear seats down, moved everything forward as far as possible, rearranging the load to move the heaviest items furthest forward. Result? The tendency to sway completely disappeared.
Bill

Here's a thought about xtra weight in the back of the tow vehicle.

Most wt distribution system setups are adjusted to the normal trailering tongue weight + normal trunk wt.

Assume a tongue wt of 450 lbs + 100 lbs in the trunk. Then the equalizer is adjusted such that the % of down force on the tow vehicle (say 350 lbs) of the trailer and trunk is distributed evenly between the front and rear wheels. Vehicle  squats a bit, but stays level. Steering power is normal.

When an extra 200 lbs (f'rinstance) is loaded at the rear, the equalizer, not having been readjusted, will NOT respond properly. The front of the vehicle rides higher. Result - steering power decreases and any trailering loads which "tend" to produce sway will be more destabilizing. The extra weight in the rear of the tow vehicle also is destabilizing once lateral motion begins. Double wammy!

Them's my thoughts, taken from 30 yrs in aviation. An analog to the above would be reducing the designed size of an airplane's vertical stabilizer. Any gusts producing yaw would take longer to damp out - and in the worst case could cause loss of lateral control.

I may be wrong, but what I've said seems dynamically consistent with my own experience in aviation.


Denny_A

I agree with DenTed and share your hypothesis...

I once roade in a Vanagon with 12 boyscouts and the front wheels were barely on the ground!  Talk about sway problems!!

Whenever I pack my truck for our camping trips, I lay  our seats down and the heavy stuff goes in front of the rear axle as much as possible.  As an added bonus, my my truck was really loaded down when my RV dealer adjusted my equalizing hitch, so I know the set up is good for my "camping" load.

65 to 70? That's illegal in Illinois where I trailer most of the time.
Sorry, couldn't resist....
Dick_B

What is the speed limit in Illinois? I hope it is at least 65 mph.

As previously mentioned you want to put items in the trailer on or forward of the axle to help properly balance the load, but the back of the tow vehicle is also part of that equation.  

One thing that was suggested about handling sway is to apply the trailer brakes judiciously.  According to some, this can quickly negate the sway which would be aggravated by applying both the trailer and tow vehicle brakes at the same time.