TM Towing Problems

It can't be emphasized enough that putting bike racks and all kinds of heavy loads behind the axle of a TM is toying with danger! The proper place to carry your bikes is somewhere else, such as on the roofs of your tow vehicles. If you're going to push the center of gravity of your TM to the rear of its axle, you're going to induce swaying.

Recently a familiy in our church was involved in a bad accident that was caused by swaying of their 5th wheeler. When gusts of wind somewhere in Nevada caused the husband to lose control of the trailer, both tow vehicle and trailer rolled over several times. He and his granddaughers had minor injuries but his wife sustained a broken neck. Fortunately she had no paralysis, but had to undergo surgery and wear a "Halo" neck stabilizer for many weeks.

The primary reason most of us purchase TMs is because they have marvelous towing characteristics. Why, then would any TM owner knowingly degrade those characteristics - to flirt with injury and death.

A sway control device may dampen out some side-to-side oscillations caused by a rearward center of gravity. All it may take, however, to overpower your sway controller is a strong gust of wind or any oily patch of roadway. In a few seconds your pleasure trip has turned into a disaster.

I've experienced severe swaying a couple of times while towing small trailers. Both times the trailer was small enough that it couldn't overpower the tow vehicle but, believe me, both occasions were frightening!

[G-V_Driver]

10-4 on no sway control. You shouldn't need one. I would pay anybody (other than maybe Jeff Gordon) who can make mine sway. I had a scary moment on a rainy day in Cheyenne, WY this summer when I was forced to make the most severe evasive maneuver I can ever remember. TM swerved with me, but no more.

If it doesn't sway when it's empty (take your empty trailer out on a deserted stretch of road and try to make it sway. I did and it didn't. Be sure the insurance is effect first.)

If it exhibits sway tendencies when it's full and doesn't when it's empty, you will know that loading is the problem. If it sways when it's empty, check the mechanical condition of the unit.

If your unit sways, and your TV is capable of towing it (consult your TV manual as well as numerous posts on this subject) something else is causing the problem. If the TM is structually sound (tires, wheels, springs, attachments, etc.) it's even more probable that the problem is loading.

An easy way to check (or build) your loading plan is with a bathroom scale and a simple diagram. First, weigh the stuff you know you will take. If possible, and depending on your AQ (anal quotient) write the weight on the object (unobtrusively) with a sharpie so you will know how to rearrange when you get something else that you just can't live without.

You know the axle runs between the wheels, and the wheel wells are under the cabinet. The weight of anything you store behind the cabinets reduces tongue weight and therefore decreases stability. Anything you load forward of the cabinets has the reverse effect. The further forward or back you put it, the more impact it creates on the center of gravity and tongue weight. Once you know what you take and where you put it, you will have a better idea of the impact it will have on stability. And if you move something around, you can SWAG the impact.

Be aware that the fresh water tank is (in my case) ahead of the axles and the grey water tank is aft. So if you leave with a full fresh water tank and return with a full grey water tank, you will have effectively moved the CG aft and thereby reduced the tongue weight. Water weighs 8# per gallon, so 20 gallons of water (160#) could be your single largest weight consideration.

Write down the weights of the stuff you take and keep the list in the TM. Keep another copy in the TV, so if sway starts you can review the list for the most likely culprit. "Oh, darn it, Jane, I inadvertently put my blacksmithing anvil in the back storage compartment rather than on the sofa where I usually store it."

Ray,
I am planning to add two Trojan 6V batteries to the rear of my 2005 2720SL. This will add about 120 to 144Lbs. My TV is a 2004 F150 4x4 Supercab 5.3L 3.78 with a 6.5' bed. I haven't had any problems with sway. Will this upset the cart. Will the 24Lbs make a difference if I go to the smaller battery. This mod was posted by mjlaupp in electical on 03-07-2004.


Thanks

[Denny_A]

Re: my 10-03-04 post regarding "cold" tire temp s/be 70 deg F.

Assumed 70 F is considered to be the temp appropriate for a 50 psi. Question is, what would be the appropriate pressure at a different temp. Assume the tire volume is constant (in a close-enuff-fer-gumint-work way), then P2 = P1*(T2/T1), where P is in psi and T is deg. Rankin. Math indicated a Temp change of 10 F should result in a 1 psi tire pressure change.

Sampled my tire pressure 3 days ago at 40 F and today at 70 F. Result:

P(@40 F) = 45 psi. P(@70 F) = 48 psi. Tire was not adjusted in any way. Temp change of 30 F resulted in a 3 psi change.

Although this was an obviously limited test, and a larger Temp difference would have been more statistically significant, it nevertheless appears to confirm the rule of thumb: Cold tire pressure changes 1 psi for each 10 deg F change.

Time to adjust my tire pressure back to 50 psi(translation: my tire is 2 psi underinflated) .

Denny_A

Are you suggesting that I (living in hot south Texas) should lower my psi when it is 100F? Instead of 50 it should be at 47? It seems to me that would increase heat build up and lead itself to self destruct.

Originally Posted by mjlaupp

Al,
The 2720SD should tow without sway. I doubt that your bike rack biased the weight that much to the rear. The 2720SL & 2720SD models have an extra 50-70 pounds tongue weight that should offset the weight of the bike rack and bikes.
The other thing that will cause sway is low tire pressure. They must be pressurized to 50 psi. The independent suspension on the TM will allow the unit to start bouncing from tire to tire if the tire pressure is too low. This bouncing is turned into sway by the TV/TM hitch connection.
HTH
MJL

When we arrived home I found the tire pressure in one tire a few
lbs lower than the 50PSI spec.

[Denny_A]

Al,

I believe that if the tongue weight is at least 10% or greater (of the trailer weight) there should be no problem. Therefore if lightly loaded, as you indicated, the trailer was likely near or under 3500 lbs. You had two bikes on a bumper hitch. Let's try a little math exercise using assumptions.

Assume: Trailer 3500 lbs; tongue weight (w/out rack) 12% of 3500 = 420 lbs.
N.B.: I had the geometry wrong in original post. Below was amended to reflect moment arms measured from axle attachment point on the frame.
Geometry: Axle-to-rear bumper = 7'3".; Axle-to-hitch = 12'9".; bike rack arm behind bumper approx 1 ft(?).
Bikes plus rack = 2@35 lb + 10 lb = 80 lbs total. (replace with actual weights).

Moment around trailer axle = 420 lbs*12.75 ft - 80 lbs*8.25 ft = (5355 - 660)lb-ft = 4695 lb-ft. (sum of moments)

Question: What is the new tongue weight?

Answer: Tongue Wt = Sum of moments / Arm = 4695 lb-ft / 12.75 ft = 368lbs.
Result: Tongue weight dropped from 12% to 10.5%.
Reason: Long moment arm to the bike rack.

The point - small increments of weight at a long moment arm have a large effect. The geometry is such that each 10 pound increment of additional weight behind the bumper removes about 6-7 lbs pound from the hitch. If the bikes and rack weighed more than in the example, and the hypothetical tongue weight were even less than I used, the final tongue weight could be closer to 9%.

Denny_A

Originally Posted by ColoradoAl

-------snip---------noticable sway----snip
The trailer was lightly loaded and so was the TV since we were out for a quick three day camping trip. I'm aware that it is
recommended that the bulk of the weight should be concentrated in front of the trailer axle and that's where I stowed most of the things we carried inside the trailer. However, I had the dealer install a hitch on the rear of the trailer for my bike rack and I had two mountain bikes mounted there for this trip. I just occurred to me that that could be my problem.

As a greenhorn to the trailer world, I may have shot myself in the foot. I would appreciate any constructive advice on how to deal with this fine mess I may have gotten myself into. ----snip-----------
ColoradoAl

Our 2619 had the water tank located under the driver-side dinette seat, which was located in front of the axle. One way to add tongue weight is to carry water (8#/gal). The advantage of the extra tongue weight far outweighs the disadvantage that extra weight has on mpg. Our current trailer has a 50 gallon water tank under the front-mounted queen bed. It is always full when we leave home.

I don't know where the water tank is located on the 2720SD, but if it is in front of the axle, try filling it at home and experiment with your towing stability.

Thanks for the analysis. My bikes and rack weight 95 lbs and that weight
extends about a foot behind the TM bumper. Following your work I arrived
at a TW of 359 lbs or a reduction from 12% to 10.25%.

[RockyMtnRay]

Originally Posted by ColoradoAl

However, I had the dealer install a
hitch on the rear of the trailer for my bike rack and
I had two mountain bikes mounted there for this trip.
I just occurred to me that that could be my problem.

Greetings to a fellow resident of Colorado Springs and welcome to our online community!

Yes, as Denny-A's math quite conclusively proves, putting those two bikes on the back of the trailer is undoubtedly at least 90% of the cause of your sway problem. Certainly, the other recommendations like correct tire pressure and filling the water tank will reduce the potential for sway but the solution is to get those bikes off the rear of the trailer.

As the owner of a very similar 2720SL who's had each tire of my loaded trailer weighed, I would strongly caution you to NOT fill the water tank over half full as you're very likely to exceed the axle limitation for the street-side tire if you also have a full load of food in the fridge and a filled hot water tank. Besides which, because the water tank is just barely in front of the axle on the 2720SD (and SL), its affect on the trailer's center of gravity (and anti sway stability) is pretty minimal.

IMO, bikes (or any other weighty object) simply should never be carried on the back of the smaller TMs as their weight that far behind the axle substantially reduces the inherent sway resistance of the trailer. I also think that Dave Unruh and the gang at The Car Show (presuming that's where you bought your TM) are doing buyers a major disservice by offering to install hitches on the rear bumper so people can put bikes back there.

I am overwhelmed by the large variety of anti-sway
devices and weight-distributing hitches out there.
They all seem to be designed for towing trailers much
larger and heavier than the 2720SD. Moreover, reading
through many of the posts found here, it seems like
few TrailManor owners have encountered trailer sway
and when they are loaded correctly they tow like
there's nothing back there without the need for anti-
sway devices and weight distributing hitches.

Do NOT mask your sway problem with an anti-sway device. Folks with convential TTs have to use them because they have no alternatives. TM owners have the far better alternative of relocating weight to solve the problem. Since you have a Jeep GC that can readily carry cycles on the roof rack, I'd definitely suggest that alternative. My previous tow vehicle was a Jeep Cherokee (not the GC) and a roof rack worked very well for carrying my mountain bike. Another alternative that works very well (I use it on my current tow vehicle, a Toyota Tundra pickup) is this Swagman "towing" 3-bike carrier that I bought at Camping World in Denver. You can also get them at cycle shops here in the Springs but CW was quite a bit cheaper if you are a member of their President's Club. This rack clamps over the hitch bar of the WDH and carries the bikes over the trailer's tongue. I've had zero clearance problems with the trailer and it would work equally well on your 2720SD as you also have horizontal propane tanks.