I'm trying to get my tongue loading right on my dual axle open trailer, and '05 durango (towing capacity around 7500, or 8750 if I would have gotten the lower final drive axle)

First thing I did was put the empty trailer on the hitch, and measure the height of the hitch from the ground. Then, me and my dad stood on the trailer right by the tongue (400 lbs) and measured the height again. It dropped 1.5-ish inches. Great. That means -1.5 inches is about 400 lbs of tongue weight, plus maybe 50-100 for the trailer itself (let's ignore for a second).

So, I put the car on the trailer, about centered on the front axle. The hitch was down about 4 inches, maybe 1000 lbs of tongue weight (trailer and car are 4000 lbs, so the tongue weight should be 400-600 lbs). Dang, I went way too far forward. I pull back, and back, and back, until my rear tires are about a foot from the beaver tail. Still too much tongue weight. I noticed at this point, my trailer has a slight slope upwards towards the truck, so I figure my rear trailer axle was holding more weight and becoming the pivot point that I need to center the car over.

*shrug*

How much do I care? The Truck should only have 800 lbs of tongue weight max, and the 4" (or something) drop hitch is rated at 600 lbs. Do I keep scooting the car back, get a bigger drop on the tow hitch, or say fuckit and overload the truck?

Anyone have a more reliable way to estimate tongue weight, besides a scale I think our "estimate" should be good since we have a measurement of drop with a certain (1.5" == 400 lb) weight, and spring rates should make it roughly proportional across any weight.

Let me know if you think I'm over thinking it, I can just toss the car at the back of the trailer and go.

 

Just a thought, but how much of a difference would you see if you backed the car onto the trailer (in that the front bias of the car is normally about 60-65%).

 

if you're towing with a 1/2 ton truck or better, i wouldn't even worry about tounge weight if you're tossing the R on a reasonably sized open trailer. just try and get the center weight point of the car just in front of the rear axle of the trailer.



that's what i do and i don't have any problems towing.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tnord &raquo;</TD></TR><TR><TD CLASS="quote">if you're towing with a 1/2 ton truck or better, i wouldn't even worry about tounge weight if you're tossing the R on a reasonably sized open trailer. just try and get the center weight point of the car just in front of the rear axle of the trailer. </TD></TR></TABLE>
Sounds like about what I was going to do. It should be fine, it's just that it's a new truck/trailer and my first experience towing is going to be 700+ miles one way to Watkins Glen.

Ah ha! Not perfect, but this might do.

 

Or you can do a free body diagram. If interested, I can walk you through it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by davidnyc &raquo;</TD></TR><TR><TD CLASS="quote">Or you can do a free body diagram. If interested, I can walk you through it.</TD></TR></TABLE>

I'd need to know the spring rates of the truck, the distance from the tongue to each axle, and it'd be pretty easy. I don't know the spring rates though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">
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I'm probably going to show my ignorance here but I don't follow this picture. Why do you need to use a multipier depending on the distance of the scale from tongue? Why wouldn't you just double the weight that is shown on the scale (1/2 the weight supported by the scale, 1/2 by the 2"x4" on the ground)? And why the pipes instead of just resting one end of the 4"x4" on the scale and the other on the 2"x4"? Thanks in advance for the explanation, I'm looking forward to be enlightened.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STS_Underdog &raquo;</TD></TR><TR><TD CLASS="quote">I'm probably going to show my ignorance here but I don't follow this picture. Why do you need to use a multipier depending on the distance of the scale from tongue? </TD></TR></TABLE>

Turn it upside down, and look at the 4x4 like a lever. Or, two levers if you like. Hell, how about two torque wrenches, one on each side (one to the scale, the other to the 1 foot metal pipe). The two torques in the torque wrenches have to cancel out.

Let's say the scale is 2 feet from the tongue. It is carrying 200 lbs of weight. That means it's applying 400 ft-lbs of torque at the tongue.

On the other side, the pipe has to do the same thing, and it must be 1 foot away from the tongue, so it has 400 lbs at one foot. If it wasn't 400 lbs, the torque would be off and you'd be rotating!

Total weight is 600 lbs, not just double what the scale reads, because it's farther from the tongue. It's the 200 lbs on the scale plus 400 on the pipe on the other side.

(We're adding "moments", not really torque, but I thought that analogy made sense, and the units are the same, it's the same concept)

 

Well damn. Now I gotta go measure my tongue weight again. Wonder what it's been for the last two years

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STS_Underdog &raquo;</TD></TR><TR><TD CLASS="quote">Why do you need to use a multipier depending on the distance of the scale from tongue? Why wouldn't you just double the weight that is shown on the scale (1/2 the weight supported by the scale, 1/2 by the 2"x4" on the ground)? </TD></TR></TABLE>

Derp! Here's another better example.

Look at it like an upside down teeter totter. The fat *** (pipe) sits close to the axis, the little girl (bathroom scale) sits at the far end, and the weight on the totter is just the fat *** plus the little girl.

Also-- the use of the pipe gives you an exact distance between each thing, since the 4x4 could make contact with the bathroom scale at any point on it, and it's a foot wide.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STS_Underdog &raquo;</TD></TR><TR><TD CLASS="quote">Well damn. Now I gotta go measure my tongue weight again. Wonder what it's been for the last two years </TD></TR></TABLE>

I'm sorta counting on the fact that Dodge designed trucks to be towed by people that can't tell the difference between free body diagrams and free pop tarts. I don't think I'm going to actually get that precise but it gives me something to look for.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Who ... are you &raquo;</TD></TR><TR><TD CLASS="quote">Just a thought, but how much of a difference would you see if you backed the car onto the trailer (in that the front bias of the car is normally about 60-65%).</TD></TR></TABLE>

If you get too much weight on the rear of the trailer, it will sway like a **** (ask me how I know ). You need to have a few hundred pounds of positive tonque weight to tow properly. The front to back CG on the Type R should be just rearward of the firewall. Try putting that point over or just in front of the front axle of the trailer. You should end up with positive tonque weight, but not too much. This is what I've been doing to tow with my 4Runner and 16' open and it has worked great. If for some reason, that doesn't work for you, I'd say use the configuration that puts more weight on the tonque. That truck and hitch should be able to handle the load just fine. If you get the car where you want it, but the trailer still angles up towards the truck, then you need a hitch receiver with a longer drop. You shouldn't move the car to get the trailer level, you should only move the car to get the tonque weight right. Once you get the car where you want it on the trailer, mark it and put stops there so that you can get the car in the same place every time. Good luck.

- Scott

 

Our Dakota is rated for 6010 with the factory tow package and 3.55 rear. The springs are supposed to be HD but in reality are not as strong as Dodge wants us to believe (I ruined my original set towing). Be very careful with the weight on the tongue. Whatever you do do NOT let the front end of the Durango come up very much. You can add Timbren helpers as I did and they really work. The CRX and R&R 20' aluminum trailer are a good pairing at ~3550 pounds. The position of the car is critical to get a maximum change in height of under 2" which is over 300 pounds, btw. What you have in the back or bed (will make a serious difference as well. Our trips to Watkins Glen, Pocono and BeaveRun have been fine except for the first one where the springs indeed could not handle the load and took a set that was permanent.
Our complete race package takes the truck to over 800 pounds of weight in the bed including crew. Add the tongue weight, fuel and whatnot to that and you are over the 6010. In your case you will be fine, if you believe the Gross weight decal.

As to positioning on any trailer-try to find the point where there is no change in tongue height and then go forward from there until you are at 10%-15% of the total weight of the trailer and car. This is a general rule, btw.
Happy travels-the track is simply terrific.

 

I know a guy who tows a 24' enclosed with 3000 pounds worth of racecar and chit in it with his Hemi Durango with no problems, and aside from the brake controller he hasn't had to add anything. In other words, too much tongue weight probably won't hurt much, just make sure it's not too little.