2nd update -Towing Set Up - 2008 Sienna CE

[gunter]

Hello,

I have the following set up.

2008 Sienna CE (Canadian version with towing package)
E2 Hitch (weight distribution system) 600 lbs max loaded tongue
Airlift 1000 airbags
Tekonsha - Prodigy - Electronic Brake Controller
Jayco X17Z trailer - trailer weighs 3076 lbs according to Jayco


Yesterday I went to our local dump that has a scale and determined the following:

Sienna with me inside & trailer (loaded with camping gear) = 8,002 lbs
Trailer (loaded with camping gear) NOT hooked up to Sienna = 3,439 lbs
Trailer (loaded with camping gear) hooked up to Sienna = 2,932 lbs

I calculate my tongue weight as follows = 3,439 - 2,932 = 507 lbs

Is the tongue weight too much? The E2 Hitch manual says I need between 10-15% of the trailer's weight on the tongue for the intergrated sway control to work properly. 10-15% of 3,439 lbs = 344 to 515 lbs


Today I drove down to the weigh station and determined the following:

Sienna with me inside - both axels - no trailer = 4,497 lbs
Sienna with me inside - front axel - no trailer = 2,535 lbs
Sienna with me inside - rear axel - no trailer = 1,940 lbs

Sienna with me inside - both axels - trailer hooked up = 5,026 lbs
Sienna with me inside - front axel - trailer hooked up = 2,425 lbs
Sienna with me inside - rear axel - trailer hooked up = 2,601 lbs
Trailer axel = 2,904 lbs

Based on my current towing configuration, it appears all my trailer tongue weight is on the rear axel AND weight from the front axel is being transferred to the rear axel.

It appears to me that I need to adjust my E2 Hitch to shift some weight to the front wheels.


UPDATE: After spending several hours adjusting the E2 Hitch and re-weighing everything after each adjustment, these are the final weights:

Sienna with me inside - both axels - trailer hooked up = 4,928 lbs
Sienna with me inside - front axel - trailer hooked up = 2,574 lbs
Sienna with me inside - rear axel - trailer hooked up = 2,376 lbs
Trailer axel = 2,970 lbs

All the above weights were converted from kilograms to pounds.

I was able to "shift" some weight back onto the front wheels AND back onto the trailer.

Any and all thoughts/comments would be greatly appreciated. My principle concern is safety and not damaging anything.

Thank you for your time and effort.

Gunter

[brian_bp]

Everything is within limits, and certainly seems reasonable to me. Yes, the trailer and it's tongue weight are near limits, but they are still under them.

The tongue weight is higher than required for the trailer, but that's what the WD hitch is for... it's just not being used yet, and needs to be to limit stress on the rear structure of the van. Yes, the rear axle is the fulcrum of a lever, and the tongue weight pressing down on the hitch pries load off of the front axle - with the Sienna's proportions, about 40% (or more due to the extra length of the WD head) of the hitch weight. The WD system needs to be adusted to bend the spring bars more and bring the front axle load back closer to the load without the trailer.

The hitch doesn't need hitch weight to work to control sway, because it is not affected by the load on the ball at all, but it does need force on the bars to cause friction and you wouldn't want the resulting forward load transfer if there wasn't some hitch weight causing rearward load transfer.

It is strange to see weights in Canada in pounds - are they converted from kilograms?

[brian_bp]

It is strange to see weights in Canada in pounds - are they converted from kilograms?

All the above weights were converted from kilograms to pounds.

That makes sense - I have converted metric values to pounds for the convenience of the majority of SiennaChat members, too.

One reason that I was curious about this is that scales large enough for vehicles are impressively accurate, but still don't have one-pound precision, repeatability, or accuracy. In this case, all of the scale readings appear to be multiples of 10 kg (22 lb), because 10 kg is the precision of the scale - no matter how well the scale works, the reading could be 5 kg higher or lower than the actual weight. If you get a weight reading, remove the load, and replace exactly the same thing, the reading may not be exactly the same, because the repeatability is also not zero - if, for instance, the scale was generally reading high, it would not be always high by the same amount.

I would consider each reading to be correct +/- 10 kg (22 lb). Calculated values could be even further out, because the inaccuracies accumulate. For instance, the hitch weight was (correctly) calculated as 3,439 - 2,932 = 507 lbs; this was 1560 - 1330 = 230 kg. Due to the uncertainty in readings, this could really be
as high as (1560+10) - (1330-10) = 250 kg or
as low as (1560-10) - (1330+10) = 210 kg,
or in other words, 230 kg +/- 20 kg, or 507 lb +/-44 lb

My point is just that when the numbers don't quite seem to add up sometimes, that's not necessarily due to anything being done incorrectly, or any failure of the logic used to analyse the situation.

An example...
Adjusting the WD system shifted 149 lb to the Sienna's front axle, and 66 lb to the trailer's rear axle, but only shifted 225 lb from the Sienna's rear axle. The total obviously should stay the same, but there's enough uncertainty in each calculated number that they are consistent within expectations.

[brian_bp]

I have the following set up.

2008 Sienna CE (Canadian version with towing package)
E2 Hitch (weight distribution system) 600 lbs max loaded tongue
Airlift 1000 airbags

...

UPDATE: After spending several hours adjusting the E2 Hitch...

I think that the airbags are a great idea, especially without a WD hitch, but even with WD. They do introduce a challenge, because every time the WD system is adjusted the rear suspension load changes and thus so does the rear suspension height; however, every time the air in the bags is adjusted to correct the suspension height the angle between hitch and trailer changes and thus so does the bending of the spring bars and thus the action of WD system. It could be frustrating going back and forth to settle on the right combination.

[brian_bp]

Sienna with me inside - front axel - no trailer = 2,535 lbs
Sienna with me inside - front axel - trailer hooked up = 2,425 lbs

The WD system needs to be adusted to bend the spring bars more and bring the front axle load back closer to the load without the trailer.

UPDATE: After spending several hours adjusting the E2 Hitch and re-weighing everything after each adjustment, these are the final weights:
Sienna with me inside - front axel - trailer hooked up = 2,574 lbs

These three scale readings show the Sienna's front axle loads without trailer, with the effect of adding the trailer but without the WD system working, and after final adjustment. The front axle load after adjustment should be close to but not any higher than before adding the trailer, and in this case it is essentially the same, allowing for all of that scale reading error.

Success!

[gunter]

Hi Brian,

Thank you very much for helpful and informative comments.

One thought.... Should I back off the WD one adjustment (washer)? When I do, the front axel weight with the trailer is the EXACT same as the front axel weight without the trailer.

I realize the scale accuracy of +-10 kgs is the wildcard.

Gunter

[brian_bp]

hould I back off the WD one adjustment (washer)? When I do, the front axel weight with the trailer is the EXACT same as the front axel weight without the trailer.

My initial reaction is yes, because that would give the correct setup, and because over-application of a WD system causes instability by denying the rear tires of traction they need to control the mass at the rear of vehicle and front of the trailer.

I do realize that many people apparently successfully operate rigs with far greater load transfer to the front, that there is lots of margin to the front axle capacity (but will there be when the whole family is loaded in?), and that more front-biased load distribution means more drive traction for slippery slopes. I should also note that I am interested in the way WD systems work, and have worked through the physics of the configuration, but I do not have experience towing with WD.