Yet Another Towing Calculation

[12stepper]

Hi, I have a 2005 Toyota Sienna and have been shopping for a pop-up.  I have tried to figure out the best tradeoff between weight (want less) and size (want more) that can be safely towed.  Since bikes and people and stuff are sometimes hard to estimate, I was willing to build in a safety factor and get a lighter pop-up.  Please let me know what you think of my calculation below..it assumes a bit of a bigger pop-up.

I believe these numbers are correct:

GCVWR for 2005 Sienna is purported to be 8800 lbs.
Curb weight is 4120 lbs (assume this means 'in drivable condition', w/ gas, etc.)
I then subtract 8800 - 4120 = 4680 lbs. to start seeing what happens when I account for the trailer weight, and weight of people and gear.

Assume the loaded trailer is 3450 lbs (which is the GVWR of the camper I'm looking at in this scenario, and just below the 3500 lb tow rating of my vehicle, which I realize is less critical than looking at GCVWR, from what I've read here).

So from above I got 4680 lbs (roughly the amount of weight that I can add to the van before reaching the combined weight limit -- GCVWR -- of 8800 lbs) and if I subtract the most my trailer can ever be (3450) I get 1130 lbs.  

So, based on this, I should never add more than 1130 lbs of anything...bikes, people, gear, etc, to the van.  Two adults and two older kids can approach half of that, leaving maybe 600 lbs for gear, bikes.  In one sense, this seems to be cutting it close.

Fudge factors:

There is a built in fudge factor above...that is, assuming the loaded trailer weighs 3450 lbs.  "Unloaded Vehicle Weight" for this camper is 2485 lbs, almost 900 lbs less.  So I guess it's important to know what the real number is, but I'd bet it's somewhere in between, but not right up to 3450 lbs.

Am I cutting it too close w/ this camper?  Assume some flat driving and some moderate (Blue Ridge) hills.

Thanks for allowing me to beat this not-quite-dead horse.  I appreciate your insights.

[AustinBoston]

Without going into details about the numbers, there is one thing you will need to do.

Once you are set up and ready to go, at least once (once a year is better) go to a truckstop with a scale and get weighed.

With this setup, you will be in a range where you can comfortably tow safely, but you can also easily get overloaded.  The only way to know for sure is to get weighed.  If you are on the scale and find you are over, take note and make adjustments.  If you find you are well under, then you can be a little less weight-stingy.

Then quit worrying and go out and camp!

Austin

[wavery]

Hi, I have a 2005 Toyota Sienna and have been shopping for a pop-up.  I have tried to figure out the best tradeoff between weight (want less) and size (want more) that can be safely towed.  Since bikes and people and stuff are sometimes hard to estimate, I was willing to build in a safety factor and get a lighter pop-up.  Please let me know what you think of my calculation below..it assumes a bit of a bigger pop-up.

I believe these numbers are correct:

GCVWR for 2005 Sienna is purported to be 8800 lbs.
Curb weight is 4120 lbs (assume this means 'in drivable condition', w/ gas, etc.)
I then subtract 8800 - 4120 = 4680 lbs. to start seeing what happens when I account for the trailer weight, and weight of people and gear.

Assume the loaded trailer is 3450 lbs (which is the GVWR of the camper I'm looking at in this scenario, and just below the 3500 lb tow rating of my vehicle, which I realize is less critical than looking at GCVWR, from what I've read here).

So from above I got 4680 lbs (roughly the amount of weight that I can add to the van before reaching the combined weight limit -- GCVWR -- of 8800 lbs) and if I subtract the most my trailer can ever be (3450) I get 1130 lbs.  

So, based on this, I should never add more than 1130 lbs of anything...bikes, people, gear, etc, to the van.  Two adults and two older kids can approach half of that, leaving maybe 600 lbs for gear, bikes.  In one sense, this seems to be cutting it close.

Fudge factors:

There is a built in fudge factor above...that is, assuming the loaded trailer weighs 3450 lbs.  "Unloaded Vehicle Weight" for this camper is 2485 lbs, almost 900 lbs less.  So I guess it's important to know what the real number is, but I'd bet it's somewhere in between, but not right up to 3450 lbs.

Am I cutting it too close w/ this camper?  Assume some flat driving and some moderate (Blue Ridge) hills.

Thanks for allowing me to beat this not-quite-dead horse.  I appreciate your insights.

You did that well

Now that you are fairly sure that you don't exceed your GCWR, just be sure that you don't exceed an other weight ratings IE, Tires, Frt & RR axles, tow rating, tongue weight etc.

I'd say that you got an "A" on that little exercise. It took me awhile to figure all that out at first. Once I realized that the tow rating means very little on it's own and that there are very many of the individual weight ratings that must be considered when towing, I was amazed at how complicated it all became.

[coach]

What's the weight carry tongue weight limit for your hitch? 350 lb?
won't you be over that? anything over 350 lb needs a WDH?

[12stepper]

The listed tongue weight rating on my Class II hitch is 350 lbs.

If properly setup, I should be able to stay below that, and still be w/in the 9 to 11% range I have seen recommended for actual tongue weight (that is, 9 to 11% of fully-loaded trailer weight, or GVWR, which for this trailer in question is 3450 lbs (resulting in a corresponding recommended tongue weight of 345 lbs).

However, I don't think tongue weight just magically falls into a certain range...I would imagine I should have to weigh it.  If I can find a bathroom scale that accurately goes up to 350 lbs (they probably make more of those nowadays!) I should be able to see whether it is too heavy or (equally problematic) too light, right?

Not sure how to compensate if it is too light.  Load up the trailer more?

I was planning to look into the weight distribution bars anyway, to find out if they provide better control in any event.

[AustinBoston]

The listed tongue weight rating on my Class II hitch is 350 lbs.

Far more important than the dead weight rating of the hitch is the dead tongue weight rating of the vehicle.  It's not about causing the hitch to fail, but overloading the rear suspension.  I've owned an otherwise very capable tow vehicle that had a 200 lb. tongue weight rating and a 6,000 lb. usable tow capacity.  That same vehicle had a class IV hitch with a 500 lb. tongue weight rating.  A 350 lb. tongue weight trailer would seem to be OK, but it would have been truly unsafe.  Excessive tongue weight can cause steering problems and cause the rear suspension to be damamged.

BTW, on that vehicle with the 200 lb. tongue weight rating - the rating went to 750 lbs. with a proper equalizing/weight distributing hitch.  The rating with air bags? Still 200 lbs.

Austin

[coach]

The listed tongue weight rating on my Class II hitch is 350 lbs.

If properly setup,

IMO, properly setup means a class III hitch and litght duty WDH. Brake controller for trailer brakes. It is a front wheel drive vehicle, right? And you'll pack heavy stuff behind the rear axle? Tow package? ...

Good luck!

[12stepper]

IMO, properly setup means a class III hitch and litght duty WDH. Brake controller for trailer brakes. It is a front wheel drive vehicle, right? And you'll pack heavy stuff behind the rear axle? Tow package? ...

It's a FWD minivan, probably the heaviest thing behind the rear axle will be the camper on the ball.  I do have the brake controller, and the minivan came w/ a tow package (window sticker said "3500 lb Tow Prep Package - heavy duty radiator, fan 150 amp alternator and power steering oil cooler").  I may consider the WDH, particularly if it adds a margin of safety/improved handling.  

Far more important than the dead weight rating of the hitch is the dead tongue weight rating of the vehicle.

Not sure what "dead tongue weight rating of the vehicle" means, the only number I see is on the hitch which was installed aftermarket, and that rating says 350lbs. Can you elaborate on how one can come up w/ a tongue weight rating of the vehicle (it sounds like what the rear suspension can handle?).  Is it based on experience, or a specification of the TV, or some type of calculation?  

Thanks all for the input, by the way.  This has been extremely helpful.

[AustinBoston]

Far more important than the dead weight rating of the hitch is the dead tongue weight rating of the vehicle.
Not sure what "dead tongue weight rating of the vehicle" means, the only number I see is on the hitch which was installed aftermarket, and that rating says 350lbs. Can you elaborate on how one can come up w/ a tongue weight rating of the vehicle (it sounds like what the rear suspension can handle?).  Is it based on experience, or a specification of the TV, or some type of calculation?

"Dead" tongue weight rating is the tongue weight rating without using a WDH or equalizing hitch.  It should be in the specifications of the vehicle, where you find the tow rating, GVWR, GCVWR, etc.  I've found it in the manual of every vehicle I've ever towed with...except the '04 Dodge Durango we own now.    I have not been able to find a tongue weight rating for that thing anywhere.

It is important to note that you can't exceed either the tow vehicle's tongue weight rating, the hitch's tongue weight rating, or the trailer's coupler weight rating.

Austin