shum02 wrote:



How much he spent on his hitch.

Gman22 wrote:

If there so much validity to it, why doesn't Ford mention it in my Expedition's manual?

Ron Gratz wrote:



Can you please list some factors which you consider to be much more important than TV and TT weight and explain why?

Ron

Road Ruler wrote:

If folks paid more attention to balance, aerodynamics, suspension, centre of gravity, brake controller quality/setup, and hitches they wouldn't have to be so concerned about weight and length.

Some of the best handling combinations that have ever graced this earth have....

A. A tow vehicle that weighs 1/2 as much as the trailer and

B. A 30' plus trailer that is being towed by a TV that has a wheel base less than 120"

roughing_it wrote:

---Regarding sway stability, here are is my prioritized list that is backed up by a theoretical understanding and some instrumented testing:
1. Yaw inertia of the trailer - lower is better (see http://www.towingstabilitystudies.co.uk/measuring_stability.htm) for more information. This is very important, but hard to measure. In my pop up, the cargo weight is a much more significant part of the total weight and when I loaded for low yaw inertia, the sway was much better. I have also done experiments where the tongue load is always 10%, but we varied the yaw inertia and it had a huge effect on the sway stability.
2. Longer axle to ball distance, this tends get longer with longer trailers, so it is rarely something that distinguishes TT's from each other. However boat trailers tend to have this distance be longer than TT's and also have lower tongue weights and you generally see much fewer anti-sway devices on boat trailers.
3. Tongue weight - more is better
4. Trailer tires (cornering stiffness which is influenced by inflation pressure and tire type)
5. Tow vehicle rear overhang to wheelbase ratio (less overhang is better, longer wheelbase is better, consider shortening your ball mount)
6. Tow vehicle wheelbase - longer is better
7. Tow vehicle cornering stiffness - higher is better (this is a function of the tires and suspension. Also heavier vehicles tend to have higher cornering stiffness)

Quote:

I have never used or tested a Hensley (or ProPride), but I can see that it does 2 things:
1. It makes the trailer better behaved because the pivot point is further away from the trailer axle(s) which reduces the tendency for the trailer to sway.
2. It makes the tow vehicle much stiffer laterally since the lateral loads go in something like 55 inches forward of the hitch, so the overhang is around zero.

npenn wrote:



Engineers use facts from calculations that are extremely accurate and do not rely on experiences and unfounded assumptions. Most calculations are conservative and allow for the many other variables as noted in this thread. Deviating from the calculations requires other factors to be in specifications or even better then specifications. Does not mean that one cannot as you pointed out deviate from the numbers and not achieve success. However, doing so raises the possibility of failure and the potential failure may occur under circumstances that have not presented themselves under your experiences.

That said, the formulas help make decisions especially when one is trying to vary more then a small deviation from the calculations. Lets say the TV can handle a 23 ft. TT but you are looking at 32 ft models that are in your GVW. I would suggest you consider a new TV or a smaller TT. However, if you are looking at a 25 ft TT with all other properties correctly configured then this deviation maybe acceptable.

I respectively disagree with your junk comment, the calculations are a very good reference point and should be considered.

Travel Safe

Ron Gratz wrote:


Perhaps we could limit this discussion to the more "conventional" TV/TT combinations -- i.e. the vast majority which are not an Airstream trailer towed by a Dodge Intrepid (or something similar).

Quote:

Those old formula are still valid.

Quote:

The physics of towing travel trailers has not changed.

Ron Gratz wrote:


Nobody seems to know how or by whom the old "formula" was derived; so it's pretty hard to know if it was ever valid. Perhaps it has some merit if you want to tow a 1950s/60s TT with a 1950s/60s sedan.


I agree. Physics has not changed. However, tow vehicles and travel trailers have changed.

The formula says that a 130" WB 3/4 ton Suburban cannot safely tow a TT longer than 25'. And, we must assume the 25' is ball-to-bumper since the formula does not state otherwise.

I doubt the formula was based on physics. More likely, it was based on loosely-applied statistics for TV/TT combinations of the day. Physics says TT weight should matter; the formula says it does not. Physics says TV weight should matter; the formula says it does not. Physics says TV rear overhang should matter; the formula says it does not.

There are better ways of determining how much a TV can tow.

Ron